A C - 2 2 5 0 WESTERN DIGITAL NO MORE PRODUCED Native| Translation ------+-----+-----+----- Form 3.5"/SLIMLINE Cylinders 2233| 1010| | Capacity form/unform 256/ MB Heads 3| 9| | Seek time / track 13.0/ 4.0 ms Sector/track | 55| | Controller IDE / AT Precompensation Cache/Buffer 64 KB Landing Zone Data transfer rate 3.000 MB/S int Bytes/Sector 512 5.750 MB/S ext Recording method RLL 1/7 operating | non-operating -------------+-------------- Supply voltage 5/12 V Temperature *C 5 55 | -40 60 Power: sleep 0.3 W Humidity % 8 80 | 5 95 standby 0.3 W Altitude km -0.305 3.048| -0.305 12.200 idle 1.5 W Shock g 10 | 70 seek W Rotation RPM 3322 read/write 3.0 W Acoustic dBA 36 spin-up 12.0 W ECC Bit REED SOLOMON MTBF h 250000 Warranty Month 24 Lift/Lock/Park YES Certificates CSA,SDA,FCC,IEC950,TUV,UL1950 ********************************************************************** L A Y O U T ********************************************************************** WESTERN CAVIAR AC1170/AC2250/AC2340 TECHNICAL REFERENCE MANUAL +---------------------------------------------------------+ | |XX | |XX J2 | |XX Inter- | |XX face | |XX | |.X | |XX | |XX | |XX | |XX | |X1 | |+-+ | || |J8 | |+-1 | |XX Power | |XX J3 +---------------------------------------------------------+ 1 ********************************************************************** J U M P E R S ********************************************************************** WESTERN CAVIAR AC1170/AC2250/AC2340 TECHNICAL REFERENCE MANUAL Jumper setting ============== J8 Master/Slave/Cable Select Configuration ------------------------------------------- +5-3-1+ Single Drive +5-3-1+ Master Drive |o o o| Configuration |X o o| Configuration |o o o| |X o o| (Dual Drives) +6-4-2+ +6-4-2+ +5-3-1+ Slave Drive +5-3-1+ Cable Select |o X o| Configuration |o o X| Configuration |o X o| (Dual Drives) |o o X| (Dual Drives) +6-4-2+ +6-4-2+ The Caviar can be assigned as either a single, master, or slave drive. Single Drive Mode ----------------- If you are installing the Caviar drive as the only intelligent drive in the system, you do not need install jumpers on the J8 connector. This is considered a standard single drive installation, and no jumpers are required. Note that even with no jumper installed, the Caviar checks the DRIVE ACTIVE/SLAVE PRESENT (DASP) signal to de- termine if a slave intelligent drive is present. If you have a dual installation (two intelligent 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 Caviar. 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 powerup reset. This feature prevents overloading of the power supply during powerup. 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. 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 ********************************************************************** I N S T A L L ********************************************************************** WESTERN CAVIAR AC1170/AC2250/AC2340 TECHNICAL REFERENCE MANUAL Notes of Installation ===================== Installation direction ---------------------- horizontally vertically +-----------------+ +--+ +--+ | | | +-----+ +-----+ | | | | | | | | | +-+-----------------+-+ | | | | | | +---------------------+ | | | | | | | | | | | | | | | | | | +---------------------+ | +-----+ +-----+ | +-+-----------------+-+ +--+ +--+ | | | | +-----------------+ Orientation ----------- The Caviar can be mounted in many different ways depending upon the physical design of your system. 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 mother- board, 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 Caiar 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 mother- board or adapter card. Dual Installations ------------------ Dual Installations require a master/slave drive configuration, where one drive is designated as the promary (master) drive and the other is designated as the secondary (slave) drive. The Caviar drive is compatible in dual installations with other intelligent drives that support a master/slave configuration. If your installation requires the use of an adapter card, it is useful to know that you may also be able to connect your floppy drive(s) to the adapter card. Mounting the Drive ------------------ For dual installations, it is usually easier to completely install one intelligent drive in the lower position first. The order of intelligent drives is unimportant if you are using to 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 to minimize the noise which is induced on the data and control buses. Also, if you are connecting two drives together, you need a daisy- chain cable that has three 40-pin connectors. 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 J2 connector. The female connector on the interface cable should have a plug position 20 to prevent incorrect connection. Make sure that pin 1 on the cable is connected to pin 1 on the connectors. Mounting Screws --------------- Mount the caviar 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. Power Connectors and Cables --------------------------- Power Connector: 4-pin MOLEX P/N 15-24-4041 or equivalent Mating Connector: Body AMP 1-480424-0 or equivalent Pins AMP 60619-4 or equivalent Power Cable Wire Gauge 18 AWG Buffer RAM ---------- A 32/64-Kbyte (optional 128/256-Kbyte) static RAM buffer enhances data throughput by buffering sector data between the Caviar and the AT system bus. The buffer is accessed by two channels, each having a separate 16-bit address and byte-count register. The channels operate simultaneously, accepting read and write operations from two data paths. Spindle Motor ------------- The spindle motor assembly consists of a brushless three-phase motor, spindle bearing assembly, disk mounting hub and a ferrofluid magnetic seal. The entire spindle motor assembly is completely enclosed in the HDA and bolted to the base casting. The motor rotates the spindle shaft at approximately 3322 RPM. Proprietary spindle electronics sense motor speed and angular position by monitoring the spindle motor's back electromotive force (BEMF). Using BEMF sensing, instead of the Conventional Hall effect ot inductive motor position sensors, lowers the power consumption and increases reliability. Motor driver circuits ynamically brake the spindle during motor spin down. 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 sectors per drive are: AC1170 - 333,300 AC2250 - 499,950 AC2340 - 666,600 Each sector consists of 512 bytes. The minimum values for any translation parameter is one. The maximum value for any translation parameter is as follows: Sectors/Track - 255 Heads - 16 Cylinders/Drive - 2048 ********************************************************************** F E A T U R E S ********************************************************************** WESTERN CAVIAR AC1170/AC2250/AC2340 TECHNICAL REFERENCE MANUAL Zoned Recording --------------- The AC1170, AC2250, and AC2340 drives employ Zoned Recording to in- crease the data density on the outer tracks of the drive. The outer- most tracks contain 71% more sectors than the innermost tracks, thereby increasing the total capacity of the drive. Advanced Defect Management -------------------------- The Caviar is preformatted (low-level) at the factory and comes with a full complement of 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 ---------------------- The Caviar festures an embedded servo concept as the means of providing sampled position feedback information to the head position servo system. 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. Servo bursts are located along a radial path from the disk center, ensuring that head positioning data occurs at constant intervals. Seek Time --------- Average Seek Sub-13 Milliseconds Track-to-Track Seek 4 Milliseconds Maximum Seek 26 Milliseconds Index Pulse Period 18 Milliseconds Average Latency 9 Milliseconds Voice Coil Assembly ------------------- The voice coil assembly consists of an upper and lower magnetic plate a flat rotary coil, a bidirectional crash stop and a pivot bearing. The pivot assembly fits in the actuator block bore. 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 sector cylinder and head numbers for all defects. The purpose of the sector/track map is to manage the reallocation of spare sectors and tracks after they have been assigned. Defects managed at the factory are sector slipped. Grown defects that can occur in the field are handled by realocation to spare sectors on the inner cylinders of the drive. Format Characteristics ---------------------- In order to be compatible with existing industry standard defect management utility programs, the Caviar supports logical format. 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 interleave table identifies any bad sectors on a given track. The interleave table must contain all appropriate number of bytes of data. There are two bytes per sector for each entry in the interleave table. The first byte marks the sector as good or bad. ********************************************************************** G E N E R A L ********************************************************************** WESTERN TIPS WESTERN DIGITAL 3.5-INCH DRIVES FREQUENTLY ASKED QUESTIONS ---------------------------------------------------------- 1) Will a Caviar drive work in my system? If your computer is 100% AT compatible and has either a 40-pin AT IDE interface on the motherboard or an IDE controller card with a 40-pin data cable. 2) What are the master/slave jumper settings on Western Digital drives? All Western Digital drives are configured the same. On the back of the drive between the 4-pin power connector and the 40-pin data connector, there is a jumper block J8 consisting of 6 pins. Western Digital hard drives are shipped with a jumper shunt in the neutral storage position (across pins 5 and 3) for future dual drive use. - If you are installing the Western Digital hard drive as the only hard drive in your system, leave the jmper shunt in the neutral storage posiition. Jumper shunts are not required for single hard drive installations. - To designate the Western Digital hard drive as the master (C:), place a jumper shunt on pins 5-6 - To designate the Western Digital hard drive as the slave (D:), place a jumper shunt on pins 3-4. 3) What are the drive type and the drive parameters in the CMOS, for Western Digital drives? On top of the drive, the number of cylinders, heads and sectors per track are printed on the label. Precomp and L-zone should be set equal to the drive's cylinder count + 1. Select user type or custom type (typically type 41 or 42) for your drive. This will allow you to type in the parameters. Older systems that do not offer a user type can either upgrade the system BIOS or set the drive to drive type 1 (which should be a smaller drive size), and run Ontrack Disk Manager from A drive to get the full capacity of the drive. If you do not follow one of these procedures and your system is pre-1994, you will be limited to the largest size drive your BIOS will allow. 4) What is the Ontrack Disk Manager software that came with my drive and what does it do? Ontrack Disk Manager is the original hard disk installation package that will initialize, partition, and prepare your hard drive for use. Ontrack Disk Manager also allows you to access the full capacity of the drive even when your system BIOS can't. It is compatible with 32-bit disk access. Note: Ontrack Disk Manager must be installed from floppy drive A. If your A drive is a 5.25-inch floppy drive, copy the contents of your Ontrack Disk Manager disk to a formatted 5.25-inch disk and re-run Ontrack Disk Manager. 5) I just installed Ontrack Disk Manager on my Caviar drive and tried to install DOS. DOS attempted to write to my drive and it formatted my drive back to 528 MB which is my BIOS limitation. How do I install DOS and still get the full capacity of my drive? After Ontrack Disk Manager installation, you must create an Ontrack Disk Manager rescue disk. There are two ways of accomplishing this: OPTION 1: - Create a clean DOS bootable disk. - Copy 2 files from the Ontrack Disk Manager disk to your bootable disk: XBIOS.OVL, and DMDRVR.BINs Create a CONFIG.SYS file on this bootable disk with these 3 lines: DEVICE=DMDRVR.BIN FILES=35 BUFFERS=35 - Remove the floppy and reboot the system. - When you see the message "Press spacebar to boot from diskette", press the spacebar (system halts). - Insert the rescue disk in the A: drive. - Press any key (system resumes boot process). - At the A: prompt, remove rescue disk, insert DOS installation disk and type SETUP. - You can now install DOS without overwriting the Ontrack Disk Manager files. OPTION 2: - Create a clean DOS bootable disk. - Insert Ontrack Disk Manager disk in the A: drive. - At the A prompt, type: DMCFIG/D=A:. You will be prompted to insert a bootable floppy in the A: drive. - Follow the prompts on the screen. Ontrack Disk Manager will ask you to change disks a few times. - Continue until Ontrack Disk Manager is finished. - Remove the floppy and reboot the system. - When you see the message "Press spacebar to boot from diskette". Press the spacebar (system halts). - Insert the rescue disk in A drive. - Press any key (system resumes boot process). - At A prompt, remove rescue disk, insert DOS installation disk and type SETUP. - You can now install DOS without overwriting the Ontrack Disk Manager files. 6) CHKDSK or SCANDISK reports a few bad sectors. How do I go about fixing the problem. You can use the Western Digital defect management utility WDATIDE. One of its options is the comprehensive surface analysis. This procedure will mark all grown defects bad if indeed there are any and it will compensate for the lost capacity by utilizing spare tracks. Note: This utility is data destructive. Back up all data on the drive before using it. Due to the thoroughness of this operation, WDATIDE can take quite a bit a time depending on the capacity of your drive. 7) Do I have to do anything with my original drive when adding a new drive to my system? Yes, one hard drive must be designated as the master drive (preferably the newer, faster drive) and the other must be designated as the slave drive. Typically, most drives need to have a jumper placed on them to specify the Master or Slave position. For information on non-Caviar hard drives, please contact the appropriate manufacturer. 8) I installed my new drive and entered the drive parameters in the CMOS, but the drive will not boot or it displays the message "HDD controller failure." Your drive must be partitioned and formatted before it will be bootable. If your system will support drives larger than 528 MB, and you have a copy of MS-DOS or PC-DOS version 5.0 or greater, insert the setup diskette in your floppy drive and turn on your computer. Follow the prompts and DOS will partition and format the drive for you. If you do not have a copy of MS-DOS or PC-DOS version 5.0 or greater, you will need to boot from a bootable disk and then run the FDISK command to partition your drive, and then format the drive using the DOS FORMAT command. After running format, you should be able to reboot your computer from your hard drive. 9) How can I use the full capacity of my Caviar drive of 540 MB or greater? You can use Ontrack Disk Manager to obtain full capacity if your system does not support LBA mode. If your system does support LBA mode, you can enable LBA in your CMOS setup utility. 10) How can I get 32-Bit Disk Access in Windows on my Caviar AC2540, AC2700 or AC31000 in Windows 3.1x? If your BIOS supports the drive at full capacity (i.e., the BIOS supports Logical Block Addressing) you use WDCDRV.386, Western Digital's FastDisk device driver. This driver is contained in a file named WIN31.EXE available for downloading from our bulletin board (714/753-1234), our Web server (WWW.WDC.COM), our FTP site (FTP.WDC.COM), our forum on the Microsoft Network (Go word WDC), and our forum on America On-line (keyword WDC). If your BIOS does not support LBA mode and you have installed your drive using Ontrack Disk Manager (v6.03 and above), run DMCFIG to install WDCDRV.386 and obtain 32-Bit Disk Access. 11) My drive will not spin up or spins down after a few seconds. This is a drive failure. Return the drive to the distributor or contact a technical support representative to receive a Return Materials Authorization (RMA). 12) CMOS, FDISK and File Manager in Windows report less than the capacity of my new drive, but CHKDSK reports the right number of bytes. Which is correct? Setup (CMOS) and FDISK use a binary definition of a megabyte which is calculated at 1,048,256 bytes per megabyte. All hard drive manufacturers and the DOS CHKDSK utility use a decimal definition of a megabyte which is calculated at 1,000,000 bytes per megabyte. This is why some utilities show 515 MB for a 540 megabyte drive and some show the actual number. 13) How Can I install OS/2 for Windows, OS/2 3.0 WARP, Windows NT 3.5x or Windows 95 on my drive which was initially installed using Ontrack Disk Manager? If you have Ontrack Disk Manager version 6.03, 6.03a, or 6.03b, download the file named DMPATCH.EXE from Western Digital's online services: ftp site: ftp.wdc.com World Wide Web Site: http://www.wdc.com/ Microsoft Network (MSN) - Go word WDC America Online (AOL) - Keyword: Western Digital Western Digital's BBS at (714) 753-1234 This file has the latest Ontrack Disk Manager drivers which will allow you to install OS/2 version 2.1x, OS/2 WARP, Windows NT 3.5x or Windows 95 on your hard drive. Please read the included readme file with this file for further detail. 14) My drive will work as a slave but not as a master (or vice- versa). Check master/slave jumpers on all drives. Also, some drive's speed and timing differ drastically as to the initial spinup sequence. This might confuse the system and cause one of the drives not to be recognized. The best solution for this situation is to exchange drives (make the master a slave and vice-versa). 15) My drive will not partition when I run FDISK. It hangs the system or it displays the message: "Runtime error." This is usually caused by corruption or damage to track zero. Use the Western Digital utility WDFMT to format the drive. If that does not help, call Western Digital Technical support at 1-800-ASK-4-WDC to get further instructions. 16) Can a hard drive be mounted on it's side, edge, or upside down? Drives can be mounted on any side but it is preferable to mount the drive right side up. It is also important to use all four screws to hold the drive firmly in place. 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. The Caviar AC21600, AC32100 and AC32500 drives monitor read error rate, start/stop count, spin-up retry count, and drive calibration retry count. 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. ==================================================================== 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.