At wit's end with a Plus - odd behavior after recap

[falen5]

remove the blue scsi and boot it with nothing attached - just the logic board

what do you get

take some good HD pictures of the board and post them here

let us all have a look - you would be amazed

 

[lostkerbal]

Do you have other ram to try? Or can you try the existing ram in pairs? (2MB at a time?)

No other RAM, I'm running the stock 1MB (4x256K).

 

[lostkerbal]

remove the blue scsi and boot it with nothing attached - just the logic board

what do you get

take some good HD pictures of the board and post them here

let us all have a look - you would be amazed

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]

Can you provide the pics of your Analog board?

 

[mrw]

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:

All Macintosh models since the Macintosh Plus... include hardware handshaking... This handshaking makes read and write
operations safe... even when using the blind transfer method.

Developer Tip: In the Macintosh Plus computer... there is no hardware handshaking on the SCSI port. Instead, software must poll to detect interrupt requests.

- 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:

https://m0001a.org/hd0_608_2GB_no_blind_lacie.hd

(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]

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:

- 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:

https://m0001a.org/hd0_608_2GB_no_blind_lacie.hd

(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!

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]

Can you provide the pics of your Analog board?

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.

 

[lostkerbal]

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:

- 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:

https://m0001a.org/hd0_608_2GB_no_blind_lacie.hd

(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!

Update: it doesn't work
I mean, it is a known good BlueSCSI with known good images for that specific machine (it worked before) and it still doesn't work. Thank you for the suggestion, but unfortunately for me, this seems to be a hardware problem.

 

[mrw]

I'm so sorry. Thank you for trying!