Disabling SCSI parity checking to dump disk on ACB4000 MFM-SCSI adapter?

Jules Richardson jules.richardson99 at gmail.com
Thu Sep 24 13:15:58 CDT 2020

On 9/23/20 3:28 PM, Michael Engel via cctech wrote:
> It seems that the problem lies in the firmware of the ACB4000, which 
> doesn´t seem to support some standard commands, e.g. the INQUIRY command. 
> Most recent Linux SCSI drivers seem to use this command.

Lack of Inquiry support seems to be quite typical for early SCSI devices, 
sadly - and the Linux kernel at least has depended on it for a very long 
time. I remember trying to work out how to bypass it in the kernel source, 
but there were so many layers of code (without any design-type docs that I 
could find) that I ended up homebrewing a SCSI controller out of a few TTL 
chips and hacking some user-land code to drive it. From what I recall (this 
was around 15 years ago now) there aren't any timeouts to worry about on 
the HBA side of things, only on the targets, so it didn't matter that it 
was slow as molasses.



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