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Jim,
1) What I was saying is that PIO can NOT deliver the performance
we need. Not because of the "burst rate", but because the CPU
is involved in every access and there is considerable delay between
every word or dword (depending if chipset supports 32-bit I/O cycles).
2) Re: OS and DMA.
Win95 yes, no DMA, but in Win98se, WinME and Win2k, I have
had VERY little problem with DMA being enabled, coming from close to 1000
first hand installs for Win2k, Win9se, Win XP.
Also as part of delivering the correct IMAGE for a given PC, we make sure
DMA is enabled (otherwise we WILL not meet the advertised
performance numbers).
So just the OPPOSITE is TRUE... ALL of our CD-ROM/DVD/HDD storage products
use and have DMA enabled (MDMA or UDMA).
If you have specific examples of a delivered Compaq system or Compaq Options
with the above OSs (98se, ME, and 2k) that did NOT come with DMA enabled,
I am ALWAYS interested in understanding what went WRONG.
I CAN NOT make any comment/assurances about
1) OSs that you install
2) drives that you buy in the channel.
Jeff
> > b) For PC storage PIO is not used (except for boot):
> > i) Significant HDD performance impact
> > ii) When using Intel Pentium II or later processors, it is
> > very difficult to support faster than 16X CD-ROM drives
> > let alone 48/52X CD, or 16X DVD drives
> > iii) DAE (digital audio extraction) even at 1X is very
> difficult in
> > PIO
>
> Someone correct me if I'm wrong... Didn't Windows 9X ship
> with DMA turned
> off by default? And even W2K appears to leave it off by
> default for most
> ATAPI devices. Linux left it off by default until recently.
> That's most
> of PC Storage right there that's not using DMA.
Jeff Wolford Email: [EMAIL PROTECTED]
Senior Storage Architect
Manager - Storage Interface and Tools - PC Storage Group
Voice: (281) 514-9465, Pager: (800) 973-5739
Compaq Computer Corporation
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