A C - 3 3 2 0 0 WESTERN DIGITAL Native| Translation ------+-----+-----+----- Form 3.5"/SLIMLINE Cylinders | 6296| | Capacity form/unform 3249/ MB Heads 5| 16| | Seek time / track 11.0/ 3.0 ms Sector/track | 63| | Controller IDE / ATA4 Precompensation Cache/Buffer 256 KB ADAPTIVE Landing Zone Data transfer rate 10.000 MB/S int Bytes/Sector 512 16.600 MB/S ext PIO4 Recording method GCR8/9PRML operating | non-operating -------------+-------------- Supply voltage 5/12 V Temperature *C 5 55 | -40 60 Power: sleep 1.1 W Humidity % 8 80 | 5 95 standby 1.4 W Altitude km -0.305 | idle W Shock g 10 | 150 seek 5.1 W Rotation RPM 5200 read/write W Acoustic dBA 40 spin-up W ECC Bit REED SOLOMON,SMART MTBF h 350000 Warranty Month 36 Lift/Lock/Park YES Certificates CE(EU),CSA,EN55022,FCC,IEC... ********************************************************************** L A Y O U T ********************************************************************** WESTERN AC11200/22000/22500/33200/34000 TECH.RE.MANUAL 79-860026-005 +---------------------------------------------------------+ | |XX | |XX J2 | |XX Inter- | |XX face | |XX | |.X | |XX | |XX | |XX | |XX | |X1 | |+-+ | || |J8 | |+-1 | |XX Power | |XX J3 +---------------------------------------------------------+ 1 J2 J8 J3 +39------------------------------------1++9-7-5-3-1++-------+ |o o o o o o o o o o o o o o o o o o o o||o o o o o||O O O O| |o o o o o o o o o o o o o o o o o o o||o o o o o||4 3 2 1| --+40------------------------------------2+10-8-6-4-2+++-+-+-++---- | | | +12V (Pin 20 keyed) | | +- GND | +--- GND +----- +5V ********************************************************************** J U M P E R S ********************************************************************** WESTERN AC11200/22000/22500/33200/34000 TECH.REF.MANUAL 79-860026-005 Jumper setting ============== J8 Master/Slave/Cable Select Configuration ------------------------------------------- +5-3-1+ Single (Neutral Position) |xxx o| Factory default. The jumper in this position has no effect |o o o| on single hard drive configurations. +6-4-2+ +5-3-1+ Cable Select +5-3-1+ Master Drive |o o X| option. |X o o| Configuration |o o X| |X o o| (Dual Drives) +6-4-2+ +6-4-2+ +5-3-1+ Slave Drive |o X o| Configuration |o X o| (Dual Drives) +6-4-2+ The Caviar can be assigned as either a single, master, or slave drive. Dual Installations ------------------ Dual Installations require a master/slave drive configuration, where one drive is designated as the primary (master) drive and the other is designated as the secondary (slave) drive. The Caviar drive is compatible in dual installations with other IDE drives that support a master/slave configuration. Jumper Settings --------------- The Caviar drive has a jumper block (J8) located next to the 40-pin connector on the drive. The Caviar can be assigned as either a single, master, or slave drive. Caviar drives are shipped with a jumper shunt in the neutral storage position (across pins 5 and 3). Single Drive Mode - If you are installing the Caviar drive as the only hard drive in the system, leave the jumper in the neutral storage position. Jumpers are not required for single drive installations. Note that even with no jumper installed, the Caviar checks the DRIVE ACTIVE/SLAVE PRESENT (DASP) signal to determine if a slave IDE drive is present. If you have a dual installation (two hard drives), you must designate one of the drives as the master and the other as the slave drive. The jumper pins on the J8 connector need to be configured for the dual installation. Master Drive Mode - To designate the drive as the master, place a jumper shunt on pins 5-6. With the Caviar configured as the master drive, the Caviar assumes that a slave drive is present. The jumper on pins 5-6 is optional if the slave drive follows the same protocol (Common Access Method AT Bus Attachment) as the WD Caviar drive. Slave Drive Mode - To designate the drive as the slave, place a jumper shunt on pins 3-4. When the Caviar is configured as the slave drive, the Caviar delays spin up for three seconds after power-up reset. This feature prevents overloading of the power supply during power-up. Cable Select (CSEL) - Caviar also supports the CSEL signal on the drive cable as a drive address selection. Place a jumper shunt on pins 1-2 to enable this option. When enabled, the drive address is 0 (Master) if CSEL is low, or 1 (Slave) if CSEL is high. Do not install the CSEL jumper shunt when installing the Caviar drive in systems that do not support the CSEL feature. J3 DC Power and pin connector assignments ------------------------------------------- +------------+ pin 1 +12 V | 4 3 2 1 | pin 2 GND +------------+ pin 3 GND pin 4 + 5 V Alternate Jumper Settings for Drives Larger than 2.1 GB ======================================================= On initial boot, the system BIOs may lock up on drives that have more than 4095 cylinders (driver larger than 2.1 GB). Alternate jumper setting have been provided for the Caviar drives that are larger than 2.1GB to overcome this system BIOS limitation. These jumper settings cause the drive to report 4092 cylinders (instead of the usual 4960,6296 or 7752) in Word 1 of the Identify Drive data. The true capacity is still reported in Word 54 and Word 60-61. All other Identify Drive data remains the same. Special software is required for DOS and Windows operating systems to utilize the full capacity of drives larger than 2.1 GB. +5-3-1+ Single Drive +5-3-1+ Master Drive |X X o| Configuration |X o X| Configuration |X X o| |X o X| (Dual Drives) +6-4-2+ +6-4-2+ +5-3-1+ Slave Drive |o X X| Configuration |o X X| (Dual Drives) +6-4-2+ ********************************************************************** I N S T A L L ********************************************************************** WESTERN AC11200/22000/22500/33200/34000 TECH.REF.MANUAL 79-860026-005 Notes On Installation ===================== Installation direction ---------------------- horizontally vertically +-----------------+ +--+ +--+ | | | +-----+ +-----+ | | | | | | | | | +-+-----------------+-+ | | | | | | +---------------------+ | | | | | | | | | | | | | | | | | | +---------------------+ | +-----+ +-----+ | +-+-----------------+-+ +--+ +--+ | | | | +-----------------+ The drive will operate in all axis (6 directions). Orientation ----------- The Caviar can be mounted in the X, Y, or Z axis depending upon the physical design of your system. It is recommended that the drive be mounted with all four screws grounded to the chassis. Screw Size Limitations ---------------------- The Caviar is mounted to the chassis using four 6-32 screws. Recommended screw torque is 5 in-lb. Maximum screw torque is 10 in-lb. Caution: Screws that are too long will damage circuit board components. The screw must engage no more than six threads (3/16 inch). Side mounted screws should engage a maximum of .188 inches (3/16"). Bottom mounted screws should engage a maximum of .250 inches (1/4"). Grounding --------- It is recommended that the drive be mounted with all four screws in the side grounded to the chassis. The drive must be grounded with at least one mounting screw. Side mounting: Use four metal screws. Top face mounting: Use four metal screws. Determining Your Configuration ------------------------------ You can configure the Caviar in one of two ways: 1. The drive is cabled directly to a 40-pin connector on the motherboard, or 2. The drive is cabled to an adapter card mounted in one of the expansion slots in the computer. Both configurations use a 40-pin host interface cable. If you are using the Caviar drive as one of two hard disk drives in the computer (dual installation), you may use either configuration. In dual installations, you must use a 40-pin host interface cable with three connectors and daisy-chain the two drives to the motherboard or adapter card. Mounting the Drive ------------------ For dual installations, it is usually easier to completely install one IDE drive in the lower position first. The order of IDE drives is unimportant if you are using two Western Digital drives. As explained previously, one must be jumpered as the master drive and the other as the slave drive. When installation is complete, the drives are daisy-chained together. Cabling and Installation Steps ------------------------------ Make sure your interface cable is no longer than 18 inches (including daisy chaining) to minimize noise that is induced on the data and control buses. When connecting two drives, use a daisy-chain cable that has three 40-pin connectors. Connectors should be placed no more than six inches from the end of the cable. If only one drive is connected, it should be placed on the end of the cable. Caution: You may damage the Caviar drive if the interface cable is not connected properly. To prevent incorrect connection, use a cable that has keyed connectors at both the drive and host ends. Pin 20 has been removed from the J2 connector. The female connector on the interface cable should have a plug in position 20 to prevent incorrect connection. Make sure that pin 1 on the cable is connected to pin 1 on the connectors. The order in which you perform the following steps will vary depending on your system. 1. Attach the end of the 40-pin interface cable to the 40-pin J2 connector on the back of the Caviar hard drive. For dual installations, connect the two drives together by using a three-connector interface cable. Match the orientation of pin socket 1 on the 40-pin IDE cable to pin 1 on the connector. 2. Thread the cable through the empty drive bay and slide in the Caviar drive. 3. Mount the Caviar drive in the drive bay using four 6-32 screws. Be sure to use the correct size screws. Do not install the screws past six threads (3/16 inch). Screws that are too long will damage the Caviar drive. For proper grounding be sure to use ALL four screws. Interface Pin 39 HDASP (I/O) Drive Active/Slave Present ------------------------------------------------------- This open collector output is a time-muliplexed signal indicating drive active or slave present. At reset, this signal is an output from the slave drive and an input to the master drive, showing that a slave is present. For all times other than reset, HDASP- is asserted by the master and slave drives during command execution. ********************************************************************** F E A T U R E S ********************************************************************** WESTERN AC11200/22000/22500/33200/34000 TECH.REF.MANUAL 79-860026-005 General Description ------------------- Western Digital's latest generation of high-performance WD Caviar drives, the AC11200/22000/22500/33200 and AC34000 Enhanced IDE hard drives, set new standards for storage, performance and reliability. With storage capacities up to 4.0 gigabytes, these wotkhorse WD Caviar drives are engineered to handle today's most storage-intensive desktop, workstation, multimedia and internet applications. Built on the proven track record of the 3.5-inch, low-profile WD Caviar design, the Caviar drives combine enhanced electronics woth leading-edge head and read-channel technology. The result is the highest WD Caviar performance ever. Advanced Product Features ------------------------- - CacheFlow5 - Western Digital's unique, fifth-generation caching algorithm evaluates the way data is read from and written to the drive and adapts on-the-fly to the optimum read and write caching methods. CacheFlow5 minimizes disk seeking operations and the overhead due to rotational latency delays. CacheFlow5 supports sequential write cache. Incorporating write cache with other CacheFlow5 features enables the user to cache both read data as well as write data. Multiple writes can now be held in the cache and then written collectively to the hard disk later. Data is held in the cache no longer than the time required to write all cached commands to the disk. CacheFlow5 constantly evaluates not only the size of the read data request but the type of data request, that is, whether the data request is sequential, random, or repetitive. CacheFlow5 selects the appropriate caching mode for optimum system performance. - Advanced Host Transfer - The AC11200/22000/22500/33200/34000 support Mode 4 PIO (16.6 MB/s) and Mode 2 multi-word DMA (16.6 MB/s) as defined by the ATA-4 standards. To achieve Mode 4 PIO burst transfers, hard disk drives must be able to throttle the host via the IORDY signal. Systems typically require a high-speed VL or PCI local bus in order to support Mode 4 PIO. - High-Speed DMA Capability - DMA Read and DMA Write commands are ATA-4 compatible and provide significant improvement in CPU bandwidth over conventional PIO data transfers. The system CPU is free to accomplish other tasks while the Caviar drive transfers data directly to/from system memory. - Power Conservation - The AC11200/22000/22500/33200/34000 supports the ATA-4 power management command set. This command set allows the host to reduce the power consumption of the drive by issuing a variety of power management commands. - Block Mode - ATA-4 compatible Read Multiple and Write Multiple commands are supported. Block mode increases overall data transfer rates by transferring more data between system interrupts. - Logical Block Addressing (LBA) - The AC11200/22000/22500/33200/ 34000 support both LBA and CHS-based addressing. LBA is included in advanced BIOS and operating system device drivers and ensures high-capacity disk integration. - Automatic Head Parking - Head parking is automatic with Caviar drives. On power down, the heads retract to a safe, non-data landing zone and lock into position, improving data integrity and resistance to non-operational shock. - Advanced Defect Management - These Caviar drives are preformatted (low-level) at the factory and come with a full complement of automatic defect management functions. Extensively tested during the manufacturing process, media defects found during intelligent burn in are mapped out with Western Digital's high performance defect management technique. No modifications are required before installation. - Embedded Servo Control - These Caviar drives feature an embedded servo concept as the means of providing sampled position feedback information to the head position servo system. Servo bursts are located along a radial path from the disk center, ensuring that head positioning data occurs at constant intervals. This high sampling rate supports the high frequency servo bandwidth required for fast access times as well as highly accurate head positioning. The embedded servo concept provides the means of generating accurate feedback information without requiring a full data surface as would a dedicated servo control concept. - Dual Drive Operation - These Caviar drives support dual drive operation by means of a "daisy chain" cable assembly and configuration options for master or slave drive designation. They also supports Cable Select (CSEL) for master or slave designation. - Universal Address Translation - These Caviar drives provide a linear disk address translator to convert logical sector addresses to physical sector addresses which provides for easy installation and compatibility with numerous drive types. - Guaranteed Compatibility - Western Digital performs extensive testing in its Functional Integrity Test Lab (FIT Lab) to ensure compatibility with all 100% AT-compatible computers and standard operating systems. - Reed Solomon ECC On-the-Fly - The Caviar implements Reed Solomon error correction techniques to obtain extremely low read error rates. This error correction algorithm corrects errors on-the-fly without any performance penalties. It allows for hardware corrections of up to a 72-bit error span on-the-fly. - Automatic Defect Retirement - If the Caviar drive detects a defective sector while writing, it automatically relocates the sector without enduser intervention. Defect Management ----------------- Every Caviar undergoes factory-level intelligent burn in, which thoroughly tests for and maps out defective sectors on the media before the drive leaves the manufacturing facility. Following the factory tests, a primary defect list is created. The list contains the cylinder, head, and sector numbers for all defects. Defects managed at the factory are sector slipped. Grown defects that can occur in the field are mapped out by relocation to spare sectors on the inner cylinders of the drive. Format Characteristics ---------------------- The Caviar is shipped from the factory preformatted (low-level) with all the known defects mapped out. In order to be compatible with existing industry standard defect management utility programs, the Caviar supports the logical format command. When the host issues the Format Track command, the Caviar performs a logical version of this command in response to the host's interleave table request for good and bad sector marking or assign/unassign the sector to/from an alternate sector. If the host issues the Format Track Command during normal operating modes, the data fields of the specified track are filled with a data pattern of all zeros. The Format Track Command can be used to mark/unmark bad sectors, and reassign unrelocated sectors. Automatic Defect Retirement --------------------------- The automatic defect retirement feature automatically maps out defective sectors while writing. If a defective sector appears, Caviar finds a spare sector. Error Recovery Process ---------------------- The Caviar has four means of error recovery: - ECC On-the-Fly - Read/Write Retry Procedure - Extended Read Retry Procedure - Extended (Firmware Assisted) ECC Correction and Realocation ECC On-the-Fly - If an ECC error occurs, the Caviar attempts to correct it on-the-fly without retries. Data can be corrected in this manner without performance penalty. Read/Write Retry Procedure - This retry procedure is used by all disk controller error types. If this procedure succeeds in reading or writing the sector being tried, then recovery is complete and the controller continues with the command. Each retry operation also checks for servo errors. This procedure ends when error recovery is achieved or when all possible retries have been attempted. Extended Read Retry Procedure - This retry procedure tries combinations of positive/negative track offsets, and data DAC manipulations to recover the data. This retry procedure is applicable only to read data recovery. The Read/Write Retry procedure is used to perform the actual retry operation. When an extended retry operation has been successful, the controller continues with the command. The controller ensures that any changes in track offset or data DAC settings that exist are cleared before the command continues. Extended (Firmware Assisted) ECC - If an ECC error is too large to correct using ECC on-the-fly, the Caviar can attempt to correct the error using Extended Error Correction. This allows correction of large ECC errors that ECC on-the-fly cannot correct. However, the Extended Error Correction process takes more time than ECC on-the-fly to return the corrected data. REED SOLOMON ECC On-the-Fly --------------------------- The WD Caviar implements Reed Solomon error correction techniques in hardware to reduce the uncorrectable read error rate. This allows a high degree of data integrity with no impact on the drive's performance. Because on-the-fly corrected errors do not require the drive's firmware to assist with error correction, they are invisible to the host system. To obtain the ECC check byte values, each byte within the sector is interleaved into one of three groups, where the first byte is in interleave 1, the second byte is in interleave 2, the third byte is in interleave 3, the fourth byte is in interleave 1, and so on. Interleaving and the ECC formulas enable the drive to detect where the error occurs. A maximum of one byte can be corrected in each interleave without firmware assistance. Firmware Assisted ECC ---------------------- With firmware assisted ECC, a maximum of 3 random bytes can be corrected in each interleave. In this case, a 113-bit single-burst error span is the maximum that is always correctable with firmware assistance because the entire error span will never occupy more than three bytes in each interleave. Universal Address Translation ----------------------------- The Caviar implements linear address translation. The translation mode and translated drive configuration are selected by using the Set Drive Parameters command to issue head and sector/track counts to the translator. Caviar supports universal translation. Therefore, any valid combination of cylinder, head, and SPT can be assigned to the drive as long as the total number of sectors is not greater than the physical limits. The product of the cylinder, head and sectors/track counts must be equal to or less than the maximum number of sectors available to the user. The maximum number of sector per drive is: AC11200 - 2,503,872 AC22000 - 3,807,008 AC22500 - 4,999,680 AC33200 - 6,346,368 AC34000 - 7,814,016 Each sector consists of 512 bytes. The values in the Sector Count Register and the SDH Register determine the Sectors Per Track (SPT) and heads. Regardless of the values of the SPT and the heads, Caviar is always in the translation mode. Power Conservation ------------------ The AC11200/22000/22500/33200/34000 support the ATA-4 power management commands that lower the average power consumption of the disk drives. For example, to take advantage of the lower power consumption modes of the drive, an energy efficient host system could implement a power management scheme that issues a Standby Immediate command when a host resident disk inactivity timer has expired. The Standby Immediate command would cause the drive to spin down and enter a low-power mode. Subsequent disk access commands would cause the drive to spin up and execute the new command. To avoid excessive wear on the drive due to the starting and stopping of the HDA, the host's disk inactivity timer should be set to no shorter than ten minutes. High-Speed DMA Capability ------------------------- By engaging an ATA-4 compatible, Mode 2 multi-word DMA, the host CPU bandwidth is increased because the peripheral data transfer burden is off-loaded to the system's DMA channel. With the exception of DMA data transfers, which are limited to Read DMA and Write DMA commands, all other commands must be performed using PIO. DMA or PIO data transfer mode selection by the host is performed on a command-by-command basis. Advanced Host Transfers ----------------------- The AC11200/22000/22500/33200/34000 support high-speed Mode 3 and 4 PIO. These are data transfer modes that utilize hardware handshaking between the host and the drive via the IORDY signal. When the drive deasserts the IORDY signal, the host extends the read/write cycle until IORDY is asserted, thereby eliminating data corruption from overrun and underrun conditions. When in Mode 3 PIO, data can be transferred in bursts to and from the host at a rate of up to 11.1 MB per second; in Mode 4 PIO, the data can be transferred at a rate of up to 16.6 MB per second. Mode 3 and Mode 4 PIO are enabled on the drive by issuing a Set Features command. If Mode 3 or Mode 4 PIO is enabled, it can only be disabled by issuing another Set Features command, a hard reset, or by cycling power. To support Mode 4 PIO, Flow Control must be enabled in the host system. If this mode is enabled on a system that does not support Flow Control, host FIFO errors can occur. Mode 3 and Mode 4 PIO timings were defined to facilitate EIDE drive integration into VL and PCI local bus systems. Zoned Recording --------------- Zoned Recording is a mechanism for increasing the capacity of the drive by increasing the Bit-Per-Inch (BPI) density of data written on the longer outer tracks of the drive. Track capacity (number of sectors) is constant within groups of tracks or zones, and is increased when the tracks are sufficiently long to accommodate a significant number of additional sectors. This incremental increase in track capacity moving outward on the disk surface creates a series of concentric zones with different data densities. Self-Monitoring, Analysis, and Reporting Technology (S.M.A.R.T.) ---------------------------------------------------------------- S.M.A.R.T. enables a drive's internal status to be monitored through diagnostic commands at the host level. These WD Caviar drives monitor read error rate, start/stop count, spin-up retry count, drive calibration retry count, G-list entry count, and multi-zone error rate. All of these attributes are updated and stored on the hard drive in the reserved area of the disk. The hard drive also stores a set of attribute thresholds that correspond to the calculated attribute values. Each attribute threshold indicates the point at which its corresponding attribute value achieves a negative reliability status. WESTERN DIGITAL Defect Management Utility ----------------------------------------- All Caviar EIDE drives are defect-free and low level formatted at the factory. After prolonged use, any drive, including Caviar, may develop defects. If you continue receiving data errors in any given file at the DOS level, you can use the defect management utility WDAT_IDE.EXE to recover, relocate and rewrite the user data to the nearest spare sector and maintain a secondary defect list. Caution: As with all format utilities, some options in the WDAT_IDE utility will overwrite user data. Dual Drive Option ----------------- WD Caviar drives support ATA-4 dual drive operations by means of configuratin options for master or slave designation. The WD Caviar is 100% ATA-4 compatible regarding the timing of the PDIAG- and DASP- signals. A jumper must be placed in the drive's option area for both master and slave configurations. If a jumper is placed in the drive's option area for both master and slave configurations. If a jumper is placed on the cable select (CSEL) option, the drive address selection will be determined by the CSEL signal on the drive cable. Connection to the host is implemented by means of a daisy-chain cable assembly. The SDH Register contains the master/slave select bit for the Caviar. The DASP- signal is a time-multiplexed indicator of Drive Active or Slave Present on the Caviar's I/O interface. At reset, this signal is an output from the slave drive and an input to the master drive, showing that a slave drive is present. For all times other than reset, DASP- is asserted at the beginning command processing and released upon completion of the comand. If the master drive option has been configured, the WD Caviar will not respond to commands or drive option has been configured, the WD Caviar will not respond to commands or drive status on the interface when the slave bit is selected in the SDH Register. ********************************************************************** G E N E R A L ********************************************************************** WESTERN ALLGEMEINES QUESTION -------- Which hard drive specification is most important to overall system performance ? - Host Transfer Rate - Drive RPM (revolutions per minute) - Disk Transfer Rate (Media Rate) - Seek Time - Cache Size - PC Data Handling - All of the above Answer ------ The correct answer is actually a combination of "all of the above," keeping in mind most of the above specifications are interrelated when it comes to optimizing system performance. The pie chart illustrates the relative influence of factors affecting drive performance during a typical random I/O operation (reading and writing to a hard drive). The major determinate of hard drive performance is mechanical factors which are one hundred times slower than the high-speed electronics contained in a drive. Factors Affecting Hard Drive Performance (In their relative order of importance) MECHANICAL LATENCIES Mechanical Latencies include both Seek Time and Rotational Latency. The seek time is a measure (in milliseconds) of how fast the hard drive can move its read/write heads to a desired location. Rotational latency is a measure of the average time (also in milliseconds) the read/write heads must wait for the target sector on the disk to pass under them once the read/write heads are moved to the desired target track. Mechanical latencies are the main hindrance to higher performance in modern Enhanced IDE (EIDE) hard drives. The time delays of mechanical latencies are one hundred times higher than electronic (non-mechanical) latencies associated with the transferring of data. Therefore, reducing mechanical latencies (a lowering of seek time and rotational latency) should be the top consideration in improving hard drive performance. RPM --- This is the rotational speed of the media (disk), also referred to as the spindle speed. Hard drives only spin at one constant speed. Typical speeds are 3600 to 3880, 4500, and 5200 to 5400 revolutions per minute. The slower the RPM, the higher the Mechanical Latencies. Disk RPM is a critical component of hard drive performance because it directly impacts the rotational latency and the Disk Transfer Rate explained below. DISK TRANSFER RATE ------------------ The Disk Transfer Rate (sometimes called media rate) is the speed at which data is transferred to and from the disk media (actual disk platter) and is a function of the recording frequency. Typical units are bits per second (BPS), or bytes per second. Modern hard disks have an increasing range of Disk Transfer Rates from the inner diameter to the outer diameter of the disk. This is called a "zoned" recording technique. The key media recording parameters relating to density per platter are Tracks Per Inch (TPI) and Bits Per Inch (BPI). A track is a circular ring around the disk. TPI is the number of these tracks that can fit in a given area (inch). BPI defines how many bits can be written onto one inch of a track on a disk surface. To greatly simplify, the Disk Transfer Rate (the rate at which data is read and written to the disk) is dependent upon the speed of the disk (RPM) and the density of the data on the disk (BPI). Even most modern, high-speed, 5000 RPM hard drives are generally limited to a maximum Disk Transfer Rate of approximately 9 to 10 MB per second. This specification is critical to performance and must be weighed carefully against such electronic latencies as Mode 3 PIO and Mode 4 PIO host transfer rates explained below. PC DATA HANDLING ---------------- After the data moves down the IDE cable from the drive to the host interface, there are several factors that can affect drive performance over which the hard drive has no control. PC Data Handling is independent from the hard drive and very dependent upon the CPU type and speed, the BIOS overhead (how the system issues commands to the hard drive), speed and size of the system RAM and RAM cache, CPU-to-memory speed, and storage subsystem performance. PC Data Handling is also affected by the caching methods of such software applications as SMARTDRIVE, 32-bit disk access operating system drivers, etc. HOST TRANSFER RATE ------------------ The speed at which the host computer can transfer data across the IDE or EIDE interface. Processor Input/Output (PIO) modes and Direct Memory Access (DMA) modes are defined in the ATA-2 industry specification as follows: Mode 3 PIO 11.1 MB/sec Mode 4 PIO 16.6 MB/sec Mode 1 DMA 13.3 MB/sec Mode 2 DMA 16.6 MB/sec Modern host computer systems usually support most of the above modes. Faster Host Transfer Rates in the future will use multi-word DMA modes as the industry will not support any future PIO mode standards beyond mode 4. The computer system manufacturer is responsible for implementing a Host Transfer Rate that is high enough to ensure that the host computer is not the performance bottleneck. Implementing increasingly higher Host Transfer Rates without corresponding increases in Disk Transfer Rates on the hard drive will not result in increased drive performance. Cache Buffer Size - Is Bigger Always Better ? A Cache Buffer is similar to a water glass. When you are writing to a hard drive, the host computer fills the glass and the disk media empties it. If you are reading data from a hard drive, the disk media fills the glass and the host computer empties it. The reason that a bigger cache buffer is not always better (or faster) is because the host computer (with Mode 4 PIO or Mode 2 DMA capabilities) can empty or fill the glass much faster than the hard drive can empty or fill it. When the host system can transfer data in or out of the cache buffer faster than the media rate, a larger buffer size becomes irrelevant because the host system is always "waiting" for the hard drive. Western Digital hard drives are designed with cache buffer sizes that are matched to the Disk Transfer Rate capabilities of the drive and the Host Transfer Rates of modern computer systems. All of our drives are benchmarked with various cache buffer sizes to verify that the most cost-effective and performance-effective cache size is implemented. Confusion Over Mode 4 and Mode 2 DMA ------------------------------------ The Enhanced IDE program created the long-range road map for performance enhancements which included faster disk and host transfers, Mode 3, Mode 4, Mode 2 DMA, etc. Currently, computer systems and hard drive controller silicon have most of the elements needed to implement Mode 4 PIO or Mode 2 DMA (a 16.6 MB/sec Host Transfer Rate). However, to take advantage of these performance modes, physical drive architecture must also make some performance improvements in the area of Mechanical Latencies and Disk Transfer Rate (media rate) as defined earlier. Some competitors, in their eagerness to supply a new feature, are prematurely marketing Mode 4 and Mode 2 DMA. While their drive controller silicon supports these modes (which is very easy and inexpensive to implement), spindle speeds (RPM), rotational latency, bit density, and other factors have not yet been improved (these being very difficult and costly). The result is hard drives which have the electronic capability to do Mode 4 and Mode 2 DMA transfer rates, but can't take advantage of these modes due to the slower Disk Transfer Rate of the drive. Western Digital will not be implementing Mode 4 or Mode 2 DMA on older drive products as the host systems into which these drives are designed are not electrically capable of these data transfers, nor are the Disk Transfer Rates on these drives beyond current Mode 3 capabilities. As next generation systems are introduced, they will be paired with next generation drives. Those drives will require and offer true Mode 4 / Mode 2 DMA capability from a total drive architecture standpoint. ==================================================================== AC2540/2635/2700/2850/21000/31000/31200/31600 Windows 95 Operating System Addendum ------------------------------------ The information in this addendum supersedes that supplied in Windows 95 section on pages 35 and 36 of this manual. Please refer to thos addendum for Windows 95 questions. Although Windows 95 is capable of recognizing the full capacity of hard drives larger than 528 MB in systems with a translating BIOS, some restrictions apply to systems without a translating BIOS. For Systems With a Translating BIOS ----------------------------------- Enter your CMOS setup and select a drive type that will recognize the full capacity of your drive. This is usually done by selecting the auto config drive tape. The boot partition can be set up to be as large as the full capacity of your hard drive. For Systems Without a Translating BIOS -------------------------------------- Enter your CMOS setup and select a user defined drive type. Enter these parameters: cylinders = 1024, heads = 16, sectors = 63. Your system's total disk space will be limited to a maximum of 528MB. If you want your system to utilize more than 528 MB of disk space, you must use Ontrack's Disk Manager software (or a similar third- party installation software). Installing Windows 95 on a Hard Drive with Ontrack Disk Manager Already Installed --------------------------------------------------------------- The Windows 95 installation program will analyze your computer system and install seamlessly with Ontrack Disk Manager. Computer Systems with Windows 95 Already Installed -------------------------------------------------- If you are installing a Western Digital hard drive and Ontrack Disk Manager on a computer system with Windows 95 already installed, you must install Ontrack Disk Manager as described here. Enter your CMOS setup and select a user defined drive type. Enter these parameters for drives with capacities over 528MB: Cylinders = 1024, Heads = 16, Sectors = 63. Save these changes and reboot your computer. 1. Select the Start icon from the Windows 95 main screen. DO NOT open an MS-DOS menu from Win 95 to install Ontrack Disk Manager. 2. Choose the Shut Down option. 3. Select Resatrt Computer in DOS mode. When your computer restarts, you should be at the DOS prompt. 4. Install Ontrack Disk Manager. Windows 95 will noe recognize the full capacity of your hard drive and run in 32-bit disk access mode for optimum performance.