X-PMC-CI-e-mail-id: 10381
RE: AHA 1542
>Decreasing speed is a good idea; I remember (now, why don't I two days
>ago) that there were/are similar problems with the Aha1542 (does anybody
>remember this one?). You have the choice to set the speed to 10 MB/s at
>the 1542-bios, but the the disk isn't found until you decrease to 5.5
>MB/s...
On many motherboards, ISA bus DMA can't run at a very fast speed even
if the spec might claim it would run at the ISA bus speed of 8MB/sec,
etc.. I don't know if the current 1542 BIOS has this feature, but the
1542 I bought about 7 or 8 years ago had a diagnostics test BIOS
function that lets the user to test how fast the DMA on the ISA bus of
the motherboard can go. My tests indicated that a couple of
motherboards I had could not go on beyond 5.5 MB/sec DMA speed, etc..
So I had to use the max DMA speed of 5.5 MB/sec, etc..
Oh. Now I understand what the 10Mb/s and 5.5 MB/s mentioned in the
post mean. I don't think that these refer to the data transfer rate
(synchronous SCSI, that is), but they may refer to the ISA DMA speed
figures whon in the 1542 BIOS setup screen. Or maybe I am wrong.
In any case, ISA-bus AHA-1542 had this ISA DMA speed constraint
and the later 2940U-whatever on the PCI-bus should have less problem
caused by the motherboard bus speed.
Back to the original problem.
> Yes, this is what adaptec suggested. I took it down to 40, and then 20
> Mbytes/s, but got the same timeout errors.
My guess is that there must be a cable (use quality cable and
don't go over maximum spec length) and terminator (use active) problem of
some sort.
Or it could be that the disk in question can't go run faster as the
poster suggested. Have you checked the spec of the disk at the
vendor's site? That SCSI-II LVD can go as fast as the max speed of
the standard doesn't necessarily mean that all the disks that are
hooked up can go at that speed.
However, if the SCSI card has a tough time
negotiating the transfer speed initially, it certainly is a problem,
but such problems are not unheard of.
--
Ishikawa, Chiaki [EMAIL PROTECTED] or
(family name, given name) [EMAIL PROTECTED]
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