Western Digital's 18Gig Ulta ATA66

Western Digital's 18Gig Ulta ATA66 - Page 1

Western Digital's 18Gig Ulta ATA66

Expert WD-AC418000

EIDE Drive technology took another leap forward this year with the advent of the Ultra ATA66 standard. Hot Hardware took a close look at a 5400 RPM ATA66 drive a few months back. This technology was fairly new then and it is still early on for the ATA66 standard. However, with the recent addition of new motherboards that are able to support this new higher bandwidth standard and DMA66 drives, we felt it was time to look at another from this field.

This is a run-down on a new drive from the perennial drive manufacturer, Western Digital. Western Digital has been around forever making high quality drives. Their reputation speaks for itself. They have recently flushed out their ATA66 Drive line-up with a bunch of 7200 RPM drives. These are drives that have a spindle speed of 7200 RPM vrs. their slower siblings at 5400 RPM. Here are the rest of the details...


  • Formatted Capacity - 18,042 MB
  • Interface - 40-pin EIDE
  • Actuator Type - Rotary Voice Coil
  • Number of Platters - 4
  • Data Surfaces - 8
  • Number of Heads - 8
  • Bytes Per Sector - 512
  • User Sectors Per Drive - 35,239,680
  • Servo Type - Embedded
  • Recording Method - PRML
  • ECC - Reed Solomon
  • Head Park - Automatic
  • 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

There are a few items on the above list that should make this drive shine. The 9 ms (milliseconds) read and 9.5ms write is pretty snappy. Although we've seen other 7200 RPM drives faster at around 7.5ms. However, this is the first ATA66 capable 7200 RPM drive we have tested. It will be interesting to see how it fairs vrs. the likes of our current in-house favorite. Another great feature for this drive is its HUGE Data Buffer/Cache Size of 2MB! This should help to balance out the somewhat average Average Seek Read and Write performance numbers.

OK, so enough with the theories. Let's get the proof from the pudding...

WD AC418000 Benchmarks here...

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