Western Digital's Expert 9.1G HDD

7200 RPM & Ultra ATA/66 - Western Digital's AC29100 7200RPM Expert™ Hard Disk Drive
With today's high speed CPUs and powerful new graphics accelerators, bottlenecks have been somewhat relegated to the IDE data bus. The Expert™ 7200 RPM family of hard disk drives from Western Digital leave conventional 5400 RPM drives behind with near 33% faster disk transfer rates. Add to the higher spindle speed, the enhanced performance and data integrity of the new Ultra ATA/66 interface , and you've got a high performance drive that is ready to meet the challenge of today's high performance system. It can even be a cost effective alternative to SCSI in SOHO workstations.


Physical Specifications
Formatted Capacity 9115 MB
Interface 40-pin EIDE
Actuator Type Rotary Voice Coil
Number of Platters 2
Data Surfaces 4
Number of Heads 4
Bytes Per Sector 512
User Sectors Per Drive 17,803,440
Servo Type Embedded
Recording Method PRML
ECC Reed Solomon
Head Park Automatic

Performance Specifications
Average Seek (Read) 9.0 ms typical, 9.5 ms maximum
Average Seek (Write) 9.5 ms typical, 10.5 ms maximum
Track to Track Seek 2.2 ms typical, 2.9 ms maximum
Full Stroke Seek (Read) 15.5 ms typical, 18 ms maximum
Full Stroke Seek (Write) 16 ms typical, 19 ms maximum
Index Pulse Period 8.33 ms (nominal)
Average Latency 4.17 ms (nominal)
Rotational Speed 7200 RPM (nominal)
Transfer Rate (Buffer to Host) 66.6 MB/s (Mode 4 Ultra ATA)
33.3 MB/s (Mode 2 Ultra ATA)
16.6 MB/s (Mode 4 PIO)
16.6 MB/s (Mode 2 multi-word DMA)
Transfer Rate (Buffer to Disk) 139.61 Mbits/s minimum
224.31 Mbits/s maximum
Interleave 1:1
Buffer Size 2048 KB (2 MB)
Error Rate (Non-Recoverable) <1 in 1013 bits read
Spindle Start Time
- From Power-on to Drive Ready
18s typical, 31s maximum
Contact Start/Stop Cycles (CSS) 40,000 minimum

Currently limited to support for Ultra ATA/66 to super7 chipsets SiS530/5595 and Via Apollo MVP4, we tested the performance of this drive on EPoX EP-MVP4A mainboard using Ziff-Davis' Winbench 99 Disk tests under the following system specifications.

Test Configuration for Western Digital AC29100
Expert 9.1G 7200RPM Ultra ATA/66

Mainboard EP-MVP4A
Chipset VIA MVP4
L2 Cache 512KB PBSRAM
Processor AMD K6-III 400MHz
Memory 1x64MB PC100
Corsair CM 654S64-BX2
Hard Drive(s) Quantum Fireball EX 12.7G Ultra ATA/33
WD Expert 9.1G Ultra ATA/66
Graphics Adapter On Board MVP4/Trident Blade3D
Using 8MB of Shared System Memory
Operating System Windows 98

We tested the drive against the Quantum Fireball EX 12.7G Ultra ATA/33 HDD using both the Ultra ATA/33 and Ultra ATA/66 interfaces by switching from the 80-wire/40-pin IDE cable to a standard 40-wire/40-pin IDE cable with the following results averaged over 5 runs of each test.

bench3.gif (8762 bytes)

bench2.gif (5686 bytes)

bench1.gif (5585 bytes)

While Western Digital's touted 33% faster data transfer rate translates through the benchmark application to more like 18-20%, the Expert is nevertheless one of the fastest IDE drives currently available.

awardgold.gif (6926 bytes) The exceptionally low CPU utilization rate in UDMA Mode 4 (Ultra ATA/66) is a major plus for multi-threaded applications and multitasking.  I have to mention also that the drive is exceptionally quiet compared to WD's Caviar drives leading to a sense of security that the drive is indeed well designed and crafted.  Temperature also does not seem to be a factor as the drive remained an exceptional cool 80-84F throughout the test period.

All in all the drive is simply first rate and seems to be very fairly priced in the $200-$230.00 price range. Personally, I am a bit more comfortable with a drive of this size over say, the WD Expert 18G HDD, as it keeps the timeframe for executing disk management utilities such as defrag, scandisk and antiviral applications down to reasonable levels without the need for creating multiple partitions.

Western Digital offers a software utility switch for disabling UDMA mode 4 so that you can purchase this upgrade drive without the need for Ultra ATA/66 chipset support especially in Intel BX, LX and ZX board's, whose Award BIOS correctly identify the interface but create conflicts since the core logic cannot support it.

To find out more about Western Digital Hard Disk Drives, visit their web site at Http://www.westerndigital.com

June 14, 1999

MediaTek All Rights Reserved