Re: 2.1.111: IDE DMA disabled?

Gerard Roudier (
Sun, 26 Jul 1998 22:59:09 +0200 (MET DST)


Just my 0.02 penguins about IDE DMA and UltraDMA.

PC_99 Chapter 18 Storage and Related Peripherals

(Requirement for Storage and Related Peripherals)

The host and hard disk devices must support bus mastering and
bus mastering must be enabled by default.
A peripheral that does not support the Ultra DMA transfer protocol
must at a minimum implement the termination scheme required for
this protocol to be tolerant of Ultra DMA.

Yes, I am a SCSI guy and I donnot really like IDE, but I can tell that
users and vendors must be very careful in following specifications
if they wan fast data transfers to work. This applies to FAST/ULTRA
20/33/40/66/80/160 MB/sec data transfers in any technology, IMO.

BTW, I am not knowledgeable at all on ULTRA/DMA, but 18.6 above seems
to indicate that ULTRA/DMA requires a termination scheme and I just
read from the list somebody reporting that he prefers to connect
UDMA HD at the end of the cable. It seems to me this is perhaps not
some preference but a _requirement_.

I also read that some less agressive timings should be used. Indeed
they can, but IIRC the Intel PIIX# less agressive timings just
drop the speed to half the maximum, thus about 16 MB/sec.
Is this still UDMA/33 ?

Dont be so nervous, be just blissfully happy. ;-)


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