the long explanation

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Subject: the long explanation
Name: ludicrous
Date: 8/31/2001 7:10:06 PM (GMT-7)
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In Reply to: Re: No (nt) posted by Chad

Okay, keep in mind as already noted in an earlier post, the fastest transfer on a SUSTAINED read for a 7200RPM IDE hard drive is generally 25-30MB/second.

An HDD, however, also has a cache buffer where data can be stored in between the drive's read/write hardware and the external data channel (in this case, IDE). Your 60GXP has a 2MB cache.

When your computer makes a request for data stored on the hard drive, if that data (or at least, the first 2MB of it) is in the cache already, the drive can "burst" it out at a rate close to the peak operating mode (usually 33, 66, or 100MB/second on modern systems).

Thus the difference between ATA/66 and ATA/100 is whether your drive can theoretically empty its cache in 30ms, or in 20ms. If the system continues to request data, the peak transfer rate will be that 25-30MB/sec mentioned earlier, regardless.

For a "typical" machine performing a variety of applications, the difference between ATA/33 and ATA/66 may be just slightly noticeable, but ATA/66 and ATA/100 will be much less so. You can install an ATA/100 card, and then if you wish run benchmarks that show it is faster, but don't expect to see any discernable real-world performance increase from it.

Where higher ATA modes come in useful is with IDE RAID, as LED mentioned. In a RAID setup the user can take two or four disks and set them to "striping mode", in which data is written in "ribbons" across the drives. So, the controller asks the first drive for data, and that drive bursts its cache. Then the controller goes to the second drive while the first one begins to re-fill its cache. The controller can then achieve a substantially higher sustained transfer rate.

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