Subject: RE: Speed of Ultra SCSI compared to Ultra DMA?
To: David Gilbert <>
From: Jonathan Belson <>
List: tech-userlevel
Date: 10/11/1998 12:26:44
On 02-Oct-98 David Gilbert wrote:
>>>>>> "Jonathan" == Jonathan Belson <> writes:
> Jonathan> Hiya A kind soul recently gave me an Adaptec 2940 Ultra SCSI
> Jonathan> card.  I was wondering how much difference in performance I
> Jonathan> would get if I moved to SCSI from my current UDMA setup.
> Jonathan> SCSI drives seem to have higher rpms on the whole, also
> Jonathan> there's the issue of CPU usage during transfers.
> Well... to compare, the 6.4 gig UDMA 7200 Quantum medalists are giving
> me about 4.5 meg/s on my FreeBSD system.  On an identically configured
> FreeBSD system, except for the 2940 (narrow ultra) and 6.4 gig Quantum
> 7200 SCSI drive, I get up to 14 meg/s.

Does an EIDE driver actually need to have specific UDMA support, or is
the performance gain automatic?