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What UDMA should be?

Posted on 2007-11-14
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Last Modified: 2013-11-14
For SATA hard drive (150Mb/s), the system show UDMA 5.
How about a SATA II hard drive(300Mb/s)? Is it UDMA 6?

However, under ATA modet UMDA 5 should be ATA100, UDMA6 should be ATA133.
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Question by:hpman820129
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by:jamietoner
ID: 20286132
Sata doesn't really have a DMA setting. Sata is a different interface from IDE. IDE drive's do have DMA settings and ata-66 is udma5 and ata-100 is udma6. I have never seen a program show a sata drive with a DMA number just sata I and sata II. Are you sure your not looking at an ide optical drive as it would be a UDMA 5 device. What software are you using to view this?
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by:garycase
ID: 20286452
jamietoner => a few corrections:

UDMA-5 is 100mb; udma-6 is 133mb.   (66mb is UDMA-4)

Optical devices almost always show as either UDMA-2 (33 mb/s) or UDMA-4 (66mb/s).


hpman820129 ==>  SATA drives are often enumerated under the ATA section in device manager (they are, after all, still ATA devices) ... and usually show either mode 5 or mode 6.   But they're actually performing at the SATA rate (150 or 300 mb/s).   Also, remember that ANY rate of 100mb/s or higher is well above the sustained transfer speed of any modern drive ... so it really makes very little difference in a drive's performance (since a very small percentage of a drive's access is at interface speeds -- only the PC-buffer transfers).    Access time and sustained transfer rate are MUCH more important than whether it's ATA-5/6 or SATA-I or II ==> that's why Raptors (which are just SATA-I drives) easily outperform SATA-II drives that rotate slower.
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by:hpman820129
ID: 20287569
I am using SATA as IDE mode.
I want to clarify the right specification, not the actual speed.

Do you mean the SATA UDMA 5 or SATA II UDMA6 is meaningless?
It they are wrong, why XP reports them?
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garycase earned 100 total points
ID: 20287633
XP is simply reporting the fastest speed the system's IDE controller supports => either UDMA-5 or UDMA-6 depending on the controller.   The actual speed is governed by the SATA interface and the attached drive (either 150mb/s or 300mb/s).
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