Re: DMA Errors - weird fix?

From: Johan Klockars <>
Date: Sat, 29 Nov 1997 14:06:36 +0100 (MET)

> I only realised the other day that I get corruption when writing to scsi
> in TC mode (without Nemesis on).

I seem to get them in all kinds of modes nowadays.
To get around the problems (rather than spend time trying to fix them), I
installed a 400Mbyte IDE drive.

> However, what intrigued me was the nature of the corruption.
> FAT1 not equal FAT2
> FAT and directories and I think files, all with a particular pattern of
> corruption at random places.

I know...

> >From memory:
> 14 bytes are shifted +16 bytes in position in the file but I think 2
> bytes are somehow skipped.
> Then alternate runs of 16 bytes are exchanged.
> At some point an extra 2 bytes is inserted and the corruption ends.

That actually sounds almost like exactly the problems I have!
When I get them, they are usually accompanied by a SCSI lockup, though.
(That is, a DMA transfer is never reported as completed.)

I asked Uwe Seimet about those rotations, thinking that there might be some
16 byte buffer in the SCSI DMA hardware that was having problems.
According to him, however, there is no such thing on the Falcon...

I'd really like to know how those rotations take place. That might give some
clue as to what's going on.

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Received on lø. nov. 29 1997 - 14:43:00 CET

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