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8-bit acorn software: other • Re: ADFS for multiple SCSI drives

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Now let's see if I can get *BYE to function correctly. For this command, I don't want to generate the 'Drive not found' error for a non existent drive. Instead, it should just skip over that drive, and move on to try stopping the next drive.
I've been having a quick look at this, but getting a bit confused. I've re-instated the original *BYE logic, which issues a SCSI (1b) stop command to all 4 drives, starting with drive 3.

Now, the SCSI stop command is almost identical to the SCSI start command. In fact it's the same 1b command but with a parameter set to 0 for stop or 1 for start. The SCSI start command is used by *MOUNT, and I had to modify the SCSI select logic slightly, so that ADFS wouldn't wait forever for BSY response from a drive controller that doesn't exist. Instead it generates a 'Not ready' error. That all works fine.

Now that I've re-introduced the *BYE logic, it starts by issuing a SCSI stop to non existent drive 3. As soon as it does this, the logic picks up that a drive controller doesn't exist at that location, and bails out with the 'Not ready' error, before the *BYE logic gets a chance to stop the spinning drives 0 & 1. This is what I expected, and is what I need to sort.

Where I'm getting a bit confused is how the original logic gets around this. The original logic also generates a 'Not ready' error when trying to issue a SCSI start (via *MOUNT) to a non existent LUN; albeit this gets done in a different place in the logic:
With the Adaptec controller, if I try to mount drive 2 or drive 3, the Adaptec LED blinks and then I get a "Not found" error more or less straight away.
...but for some reason, issuing a *BYE command, which begins by sending a SCSI stop to drive 3 doesn't generate the 'Not found' error, and therefore allows the *BYE command to also issue a SCSI stop to the remaining drives 2, 1 & 0 (some of which may also not exist).

Further head scratching required.

Statistics: Posted by KenLowe — Fri Feb 14, 2025 11:12 pm



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