UDMA-4 The missing UDMA.

[lhgpoobaa]

Every wondered about the UDMA naming convention?
You may have noticed upon bootup your devices are given a UDMA/ATA number

Thus:
ata-33 = UDMA 2
ata-66 = UDMA 4
ata-100 = UDMA 5
ata-133 = UDMA 6

But what happened to UDMA 3?

A while back reading some obscure history of IDE/ATA/UDMA i came upon the lost memeber of the family UDMA 3... apparently its ment to be 44mb/sec, and i thought i didnt exist until just now.

I got a new liteon 16x dvd drive, the 165H. Reading the doccumentation i was suprised to read

Support up to Ultra-DMA Mode 3 ( 44.4 MB/sec 0

<A HREF="http://www.jlms.com.tw/new_p_E/jlms_165X.htm" target="_new">http://www.jlms.com.tw/new_p_E/jlms_165X.htm</A>

So UDMA 3 <b>DOES</b> exist after all.


<b>Cogposto tomsa, ergo sum - <i>Descartes</i>
</b>Translation:<b> I post at Toms Hardware, Therefor I am. </b>

 

[HammerBot]

Yes, UDMA mode 3 does exists. As well as UDMA mode 0 and 1. But not UDMA mode 6. This one was invented by Maxtor and is not part of the official ATA/ATAPI standard.

According to the ATA/ATAPI 6 rev 3b standard (all the standards can be found at <A HREF="http://www.t13.org" target="_new">http://www.t13.org</A>):

UDMA mode 0 cycle time = 120 ns = 16.6 MBps
UDMA mode 1 cycle time = 80 ns = 25 MBps
UDMA mode 2 cycle time = 60 ns = 33.3 MBps (UDMA 33)
UDMA mode 3 cycle time = 45 ns = 44.4 MBps
UDMA mode 4 cycle time = 30 ns = 66.6 MBps (UDMA 66)
UDMA mode 5 cycle time = 20 ns = 100 MBps (UDMA 100)

Edit: I just looked through the current version of the ATA7 standard. UDMA mode 6 is now actually added:
UDMA mode 6 cycle time = 15 ns = 133 MBps (UDMA 133)

However, ATA7 is still only an internal working document of the committee. It is not yet approved as a standard

How old are the THGC users? Find out or contribute <A HREF="http://forumz.tomshardware.com/community/modules.php?name=Forums&file=viewtopic&p=25477#25477" target="_new">here</A>

 

[lhgpoobaa]

well its debateable if ata133 is "real" or not.
as its advertised as such and comes up as udma-6 im happy with it

Oddly, now my UDMA-3 dvd drive is showing up on bootup as UDMA-0
Go figure.

<b>Cogposto tomsa, ergo sum - <i>Descartes</i>
</b>Translation:<b> I post at Toms Hardware, Therefor I am. </b>