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

[Grant Taylor]

On 9/24/20 1:12 AM, Camiel Vanderhoeven via cctalk wrote:
> I used an Ancot Ultra2080/Lite SCSI-bus Analyzer. This is a device 
> that connects to a SCSI bus and has a serial port. Over the serial 
> port, you can monitor the signals on the SCSI bus, and use it as a 
> SCSI protocol analyzer. There’s also the possibility to construct 
> and send a SCSI command. Rather than connect a serial terminal to the 
> serial port, I connected a PC, then wrote a C program to control the 
> Ancot. I had the Ancot send commands to the disk to read a sector at 
> a time, and recorded the data sent in response to a file to create a 
> disk image. Slow as hell (each byte on the disk requires sending two 
> hex characters and a space over a slow serial line), but it works. I 
> had to make several passes over the disk, because occasionally the data 
> received from the disk turned out to be data from a different sector 
> than the one I was trying to read. By reading the disk multiple times, 
> I could get rid of these mis-read sectors.

Very NICE hack Camiel.  I like it!

I am a little surprised by getting different data for the same sectors. 
I find that mildly concerning.  Did you do something like read each byte 
multiple times to find a majority sample?  2/3, 3/5, 4/6, etc?  Do you 
think the different data was an artifact of the old drive?  Or was it a 
tickle of a bug elsewhere in the chain?



-- 
Grant. . . .
unix || die