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1996-04-27
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233 lines
[Products]
Large Disk Integration
The extensive growth in the Personal Computer marketplace, coupled with the
popularity of applications such as multimedia, gaming, and the downloading
of information from on-line have caused a great demand for larger and
larger disk drives. In order to build up the existing industry-standard IDE
interface to allow for faster, higher capacity drives, Western Digital,
along with other key industry players, led the effort to strengthen the
existing IDE interface in 1993.
The new interface, called Enhanced IDE (EIDE) removed the four primary
limitations of the existing IDE interface. These were the 528MB capacity
barrier; the IDE transfer bottleneck (faster disks); support for up to four
IDE devices; and enabling non-disk peripheral connectivity (such as ATAPI
CD-ROMs).
A New Era of Computing:
The original capacity limitation of 528MB was due to the number of bits
allocated for specifying the cylinder, head, and sector address information
at both the Interrupt 13h interface level and at the IDE interface level.
This barrier was surpassed with the implementation of EIDE by either a
software "fix" which was shipped with retail upgrade kits by Western
Digital and other leading drive manufacturers, or the addition of a
controller card, or a BIOS (Basic Input Output System) upgrade.
As the industry crossed the 1024 cylinder level with the first
"barrier-breaking" drive (drives over 528MB in capacity), BIOS developers
were facing yet another barrier at the 4095 cylinder limit. The solution
for the 1024 barrier was the translating BIOS. However, with some
implementations of a translating BIOS, a BIOS limitation occurs -- limiting
the maximum cylinders accessible by the BIOS to 4095, or 2,113,413 bytes
(4095 cylinders, 16 heads, 63 sectors, 512 bytes), or drives over 2.1GB.
BIOS Limitation:
Depending on the exact method used by BIOS developers to implement the
translating BIOS, the BIOS limitation reacts in a number of ways on drives
larger than 4095 cylinders (over 2.1GB). Distinct reactions exist with
individual BIOS s from each BIOS manufacturer. Because of the variety of
BIOS manufacturers, the number of BIOS upgrades, and the differing
timelines of OEM implementation of BIOS upgrades within system
configurations, it is difficult to predict system reactions for a specific
PC.
Western Digital's research has shown that many BIOS's dated from
approximately 1992 to February, 1996 will cause the PC to experience a BIOS
limitation upon drive installation. These PCs will require a system
limitation fix to achieve full benefit of the large drive capacity.
The following chart is an estimated percentage of systems affected by the
BIOS limitation. These figures are based on BIOS's shipped from
approximately 1992 through February, 1996 by major BIOS manufacturers.
528MB or less Truncate 5%
BIOS's 92-96 Lock-up 47%
BIOS's 92-96 Truncate 28%
New OK systems Access full capacity 5%
Unknown (misc. PC clones) ? 15%
The following reactions are seen when combining a large drive with more
than 4095 cylinders and a BIOS containing a limitation that cannot support
larger disks.
Note: BIOS manufacturers have made the required changes to their products,
and new systems moving forward should not experience the BIOS limitation.
BIOS Limitation Scenarios:
* The BIOS can view only a maximum of 2.113 GB or 4095 cylinders and
truncates, or shortens, the remaining space. In the case of a 2.5GB
drive, the end user will not be able to derive the full benefit of a
drive╞s capacity, missing approximately 400MB of capacity.
* The BIOS shortens the number of cylinders at 12 bits, limiting the
drive capacity to approximately 400MB, and losing 2.1GB.
* At boot time, the BIOS will cause a system lock-up, making the entire
system inaccessible.
BIOS Limitation Solutions:
There are numerous ways to get past the BIOS limitation in order to utilize
the full capacity of the drive, as well as any other situation caused by
the translating BIOS. Continuing Western Digital's commitment to provide
the easiest and most complete solutions to the market, each method is
detailed below. Western Digital recommends that users revise the CMOS
set-up and install the software utility. However, should this solution not
work with an individual PC, Western Digital has included an additional
solution, which includes the use of one more jumper, so that all users
should be able to gain full use of a drive. An extra jumper is shipped with
all Western Digital Caviar retail kits and distribution sales for this
specific purpose.
1. Flash BIOS Upgrade
If a system contains a flash BIOS, or user programmable BIOS chip, it
is possible to upgrade the system with a newer BIOS version that
corrects the limitation using the manufacturer's provided flash
utilities and BIOS update images. The new BIOS could correct the
limitation that causes the lock-up or truncation (space shortening)
situation so that full use of a 2.5GB drive would be possible. To find
out what type of BIOS is in an individual system, the user should
contact their system manufacturer. This solution requires no
additional software. Users may gain additional BIOS features with the
upgrade (such as bootable CD-ROM, Plug and Play features), without
added cost. However, this scenario requires some expert knowledge to
run the flash utility, and errors made during flash programming can
render a system unusable. As with the Flash BIOS, some vendors may not
have flash BIOS upgrades available. This is a difficult task to
undertake, and if not offered free of charge, can cost upwards of $35.
2. Non-flash BIOS (ROM BIOS) Upgrade:
This solution is identical to the above with the exception that the
system does not support end user reprogrammable features of the BIOS.
The user is required to obtain an upgrade ROM chip for the system,
remove the existing BIOS and install the upgrade ROM. This new BIOS
would have the ability to support drives 2.5GB or larger. To determine
the type of BIOS in an individual system, users should contact the
system manufacturer.
As with the above, this solution requires no additional software, and
the user may gain additional BIOS features with the upgrade. This
solution also requires expert knowledge, and may cause system damage
if done incorrectly. As with the above, not all vendors may have ROM
BIOS chip upgrades available, and an additional cost may be incurred.
3. Software Add-on:
In situations where the BIOS causes a truncation or shortening of
drive capacity, causing a loss of approximately 400MB, or a wrap
around BIOS-caused loss of 2.1GB, a software utility can be used to
access full drive capacity. With the software solution, the drive
automatically supports full capacity in systems with the BIOS
limitation, and no additional hardware tools are required.
To gain full drive capacity, the user needs to go through the following
steps:
- Install drive
- Boot drive
- After boot, the drive will not be able to access full capacity
- Install software, the EZ-Drive software from Micro House
International will make the remaining space available on the drive
Note: This solution alone will not work in the case of a system
lock-up as the system will lock-up prior to the boot process.
If the system supports user definable drive type, the user may choose
to configure the device for less than 4095 cylinders prior to drive
installation. Once the drive is installed, the user may then use the
EZ-Drive software to access the full drive capacity. To do this, the
user simply selects the user definable drive type option in the BIOS,
enters 4092 (to revert the system to configure the drive at 2.1GB) for
the number of cylinders on the drive, and then proceed to install
EZ-Drive. EZ-Drive is provided free-of-charge by Western Digital with
the Caviar AC32500, 2.5GB drive.
The use of the software utility does require that a user enter the
BIOS set-up and configure a drive manually. This may cause some
difficulties if the user does not have the system manual. If the
system is not user definable, the set-up program cannot be entered,
and the drive cannot be installed without a BIOS upgrade or use of the
extra jumper.
Western Digital Recommendations:
In order to provide the best possible solution for BIOS limitations,
Western Digital has opted to ship the Caviar AC32500 with the EZ-Drive
software utility, and an additional jumper (which is to be used if a system
does not support user-definable drive types). With any implementation of
these solutions, a BIOS upgrade is not necessary.
CMOS Set-up Revision and Software Utility:
Most systems can be reconfigured to gain full access of a 2.5GB drive with
a simple CMOS revision and use of the software utility. Systems generally
provide a CMOS set-up program that accesses information on system
configuration. Users should check their systems manuals for further
information on CMOS set-up.
Drive types generally offered in CMOS include auto config, user defined and
predefined. Selecting the auto config drive type automatically sets up the
Western Digital hard drive parameters. This drive type is used for DOS,
Windows 3.1x, Windows NT, Windows 95, OS/2 2.1x and OS/2 Warp. Resetting
the system configuration for auto config, coupled with the installation of
EZ-Drive should provide full access to the complete 2.5GB drive capacity.
System BIOS Doesn't Support Drives With Over 4095 Cylinders:
If a system BIOS does not support drives with over 4095 cylinders, there
are a number of solutions available. When a system locks up before CMOS can
be entered, a user can simply turn off the system, and disconnect the IDE
cable from the system in order to access CMOS set-up. This will enable the
user to then select user defined drive type, enter 1023x16x63, and
reconnect the IDE cable to the system. Combined, these procedures will
allow the user to reboot the system without locking up, and install
EZ-Drive.
Additional Jumper Usage:
Systems that do not support the user-definable drive types require one
additional step during the installation process to get to the 2.5GB
capacity point. These systems can overcome the BIOS limitation by either a
BIOS upgrade or may use a special jumper setting to access the drive. A
special jumper setting will trick the system and limit the drive at boot
time to 4092 cylinders (2.1GB), so that the BIOS will not cause a system
lock-up. Once the system has booted, the user can install EZ-Drive, which
will recognize the special configuration and jumper setting on Western
Digital drives. EZ-Drive will then query the drive for true capacity, and
set the drive system parameters to the 2.5GB capacity point.
Note: Drives configured with the additional jumper will always need to be
used with the second jumper in order to read data.
As the PC market continues to grow as a mass consumer market, Western
Digital continues to strive to present full and complete storage solutions
to the consumer. Western Digital is the only drive company to currently
provide the EZ-Drive software utility and additional jumper to its
customers to ensure the easiest transition through the BIOS limitation, and
achieve full use of large EIDE disk drives. Western Digital's charter is to
educate the consumer, and make the computing experience a less frustrating
one.
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