Information request on FMT-121 SCSI card

[Zuofu]

Hi All,

I know this is pretty obscure - but I figure I should ask here. Does anyone have any more documentation on the FMT-121 SCSI card? This was only required for the very first gen computers which don't have on-board SCSI. I saw that MAME's sourcecode had support for it:

https://github.com/mamedev/mame/blob/master/src/devices/bus/fmt_scsi/fmt121.cpp

but I couldn't find any more information on the wiring of the SCSI controller or the dedicated 30 pin connector. Also, looking at SCSI subsection of the Red Book (Section 7.6) it doesn't seem like the Fujitsu controller (MB673522U) registers match up to any of the common SCSI-1 controllers of the era (e.g. WD33C93 or NCR 5380).

I know original cards are likely to be unobtainium at this point, but does anyone have more information about this? I would be nice to make a storage emulator, but it seems like the minimal documentation in the Red Book is insufficient. Does anyone even have a picture of the board?

Thanks!

[Cyothevile]

Hi All,

I know this is pretty obscure - but I figure I should ask here. Does anyone have any more documentation on the FMT-121 SCSI card? This was only required for the very first gen computers which don't have on-board SCSI. I saw that MAME's sourcecode had support for it:

https://github.com/mamedev/mame/blob/master/src/devices/bus/fmt_scsi/fmt121.cpp

but I couldn't find any more information on the wiring of the SCSI controller or the dedicated 30 pin connector. Also, looking at SCSI subsection of the Red Book (Section 7.6) it doesn't seem like the Fujitsu controller (MB673522U) registers match up to any of the common SCSI-1 controllers of the era (e.g. WD33C93 or NCR 5380).

I know original cards are likely to be unobtainium at this point, but does anyone have more information about this? I would be nice to make a storage emulator, but it seems like the minimal documentation in the Red Book is insufficient. Does anyone even have a picture of the board?

Thanks!

I have a model 2 with that card.

Will high resolution photos be sufficient?

I hope you're doing what I suspect you're doing.

Coincidentally the mamedev has the same model2 we both have with the SCSI card

[Zuofu]

Yes, I'm basically seeing if the card can be reverse engineered. No guarantees since I'm not sure what the pinout of the 30 pin connector is (oddly it doesn't show up in the Red Book, I suppose it's considered a 'factory option') - but I figure it would be worth giving it a shot. If you have scans of the card I would really appreciate it!

[Cyothevile]

The Red book is very lacking still in documentation despite containing the most amount of information required for FMT development.

Unless you find those Fujitsu SCSI controller ICs for sale it could be a vain attempt. Well, maybe relatable scsi controllers can be used. Albeit just as slow and old as the first scsi protocols.

If you can't find any and just want to make one for yourself I can probably saved a scsi controller from a dead tower.

Which 30P connector by the way?  Are you referring to one on the side of the MB with cpu?

[Zuofu]

Which 30P connector by the way?  Are you referring to one on the side of the MB with cpu?

I'm looking at the side with the from the MB -> SCSI controller (It goes to that 30 pin 2-row IDC and right angle ribbon cable). Looking a little bit in depth at the Red Book it seems like a lot of the SCSI work seems to be done in the BIOS software. There are only 2 memory mapped registers (I guess three, one of them has different data depending on whether it's a read or write) - and one of them is just a generic 'data' register. It doesn't appear that those map directly to the MB673522U registers, although the SCSI card has very little other logic. The book also lists the SCSI phases - unfortunately without a datasheet for the MB673522U it's hard to tell what the actual chip registers might be.

My idea is if I can figure out the pinout for the 30 pin IDC connector, I can just make a direct 'registers to micro-SD card' style storage device, rather than implement the full SCSI protocol. I'm sure the MB673522U chips are unobtainable, but it can't be too hard to get an Arduino to respond to the register data directly and emulate a small hard drive on ID0. Basically what I'm trying to figure out as a first step is how read/writes to addresses 0C32h and 0C30h manifest on that 30 pin header.

[Cyothevile]

Which 30P connector by the way?  Are you referring to one on the side of the MB with cpu?

I'm looking at the side with the from the MB -> SCSI controller (It goes to that 30 pin 2-row IDC and right angle ribbon cable). Looking a little bit in depth at the Red Book it seems like a lot of the SCSI work seems to be done in the BIOS software. There are only 2 memory mapped registers (I guess three, one of them has different data depending on whether it's a read or write) - and one of them is just a generic 'data' register. It doesn't appear that those map directly to the MB673522U registers, although the SCSI card has very little other logic. The book also lists the SCSI phases - unfortunately without a datasheet for the MB673522U it's hard to tell what the actual chip registers might be.

My idea is if I can figure out the pinout for the 30 pin IDC connector, I can just make a direct 'registers to micro-SD card' style storage device, rather than implement the full SCSI protocol. I'm sure the MB673522U chips are unobtainable, but it can't be too hard to get an Arduino to respond to the register data directly and emulate a small hard drive on ID0. Basically what I'm trying to figure out as a first step is how read/writes to addresses 0C32h and 0C30h manifest on that 30 pin header.

This evening I will post very high resolution photos

Have you talked to captainys? He might have the answers you seek

[Zuofu]

Have you talked to captainys? He might have the answers you seek

Let me try emailing him, unless this forum is a better way to contact him?

[Cyothevile]

https://drive.google.com/folderview?id=1G_uoI2CcYwfhd42P49GJWjsrTXaJOB9Y


Very high resolution photos

[Zuofu]

https://drive.google.com/folderview?id=1G_uoI2CcYwfhd42P49GJWjsrTXaJOB9Y


Very high resolution photos

Great, thank you so much - this will help a ton.

I also did contact captainys, awaiting his reply.