At wit's end with a Plus - odd behavior after recap
- Thread starter lostkerbal
- Start date
lostkerbal
Active member
lostkerbal
Active member
I've booted it with and without the BlueSCSI, I had known good HD images, as well as known good 6.0.8 images, a BlueSCSI stock/preconfigured 6.0.8 image, and the 6.0.8 floppy. Without boot media, it just goes to a normal no disk screen, and the mouse moves around perfectly well. I just don't get it. Boot looks and sounds completely nominal, and the only magic smoke it's ever emitted came from the floppy drive. And that's after I booted it multiple times from the 6.0.8 floppy that just went to the same illegal instruction error.
GreenBar0n
Well-known member
Can you provide the pics of your Analog board?
mrw
Member
The Mac Plus SCSI implementation is weird. In particular, it doesn't support blind transfers, where the CPU delegates data transfer to the SCSI chip:
Macintosh disk images begin with a SCSI driver the ROM reads on start up, so when you format a SCSI disk, you install that driver. Most SCSI utilities install a disk driver that uses blind transfers because they're much faster than software polling. But the Plus doesn't support these! Instead of nicely transferred data, instead you'll see a weird error as the SCSI transfer corrupts state, like one about an illegal instruction.
The solution is to use a disk image with a driver that uses polling. As mentioned in this thread, one way to get a disk image with that driver is to format it with SilverLining. That's hard to do if you don't happen to have a working Mac already, so I made this available:
(The homepage has some information.)
I've been using copies of this since 2022 with my ZuluSCSIs and my Mac Plus; I believe this worked for @frankz as well.
I should have started a thread about this or something back then. Sorry!
- Pages 393-394, Guide to the Macintosh Family Hardware, 2nd Edition
Macintosh disk images begin with a SCSI driver the ROM reads on start up, so when you format a SCSI disk, you install that driver. Most SCSI utilities install a disk driver that uses blind transfers because they're much faster than software polling. But the Plus doesn't support these! Instead of nicely transferred data, instead you'll see a weird error as the SCSI transfer corrupts state, like one about an illegal instruction.
The solution is to use a disk image with a driver that uses polling. As mentioned in this thread, one way to get a disk image with that driver is to format it with SilverLining. That's hard to do if you don't happen to have a working Mac already, so I made this available:
(The homepage has some information.)
I've been using copies of this since 2022 with my ZuluSCSIs and my Mac Plus; I believe this worked for @frankz as well.
I should have started a thread about this or something back then. Sorry!
lostkerbal
Active member
I'll try this as soon as I can; even if it doesn't work, thank you so much for the help. It's just very weird, as my disk images used to work fine. Is there any way that a hardware issue could come up that removes drivers or make them stop working? I'm just afraid I fried the SCSI controller in some way.
lostkerbal
Active member
Can't get to it right now, but it functions perfectly, and I've double-checked all connections and cap orientations on the board; safe to say, it's a LB problem. Power and Picture are incredibly stable and clear, something's wrong with the computer itself.
