MFM controller for S-100

[MikeS]

I typed out a lengthy explanation, but accidentally clicked the back button on my Microsoft Natural Wireless Laser Mouse 7000. Probably the better half of 30 minutes was spent creating my reply. I will answer your question shortly, as i need to take a brisk walk to the coffee machine.

Been there, done that, T-shirt hanging in the closet, and feel your pain; hope there's something in your bottom desk drawer to fortify the coffee a bit ;-)

 

[Chuck(G)]

Is there a shortage of MFM controllers for the ISA bus? Since most of the (16-bit) ones, use PIO for data transfer (not DMA), might it not be more interesting to simply make an S-100-to-ISA adapter? You then get the entire range of ISA peripherals at your fingertips. Just write the drivers...

 

[fibrewire]

I am exploring a ST-506 to some standard interface. Then from the standard interface to your choice of retro computer interface.

Apparently the MFM to SASI interface already exists. This whole idea spawned from having a Corvus Systems hard disk with no interface to any computer. I just purchased a S-100 corvus interface, but I am waiting to see if it's works. I would really like a Corvus SYstems hard disk to Atari interface, but that seemed next to impossible. A guy from AtariAge said he could help, so I am gonna wait for now. What would really be cool is a SASI to USB interface. Then we could access all the rare data stored all over ebay. Hell, I would have a field day buying old drives on the cheap and seeing whats on them.

There are easier solutions i'm sure, but learning how ST-506 works would be a cool way to cut my teeth on electronics design.

 

[fibrewire]

MikeS: You had mentioned that SASI is little more than a parallel port. Is there any information you can point the way to how SASI works? I would really like to see a SASI to Atari SIO or SASI to S-100.

 

[NobodyIsHere]

Hi! I'd be willing to help make a PCB for a S-100 to ISA board assuming someone can send me a schematic. I believe this would be a lot more than just connecting the address and data busses. There would need to be some kind of signal translation for the control signals between the S-100 and ISA busses.

I am pretty swamped at the moment with other S-100 and ECB related projects so this would have to be a community effort along the lines of the boards John Monahan and I have made. The group approach has worked well for our boards, the S-100 68K CPU board, and a variety of other projects. Also working with Rich on a S-100 6502 CPU board.

Thanks and have a nice day!

Andrew Lynch

 

[monahan_z]

Andrew I made an S-100 to ISA adaptor 30 years ago (still have it here) and did a write-up about it for Sol Lib's Microsystems Journal at the time. You could use it for example with the old IBM VGA adaptor. Needless to say with the current set of S-100 boards we have in the works (new IDE, 8086, Console I/O, and 68K boards) it would be some time until we could get to it.

 

[MikeS]

MikeS: You had mentioned that SASI is little more than a parallel port. Is there any information you can point the way to how SASI works? I would really like to see a SASI to Atari SIO or SASI to S-100.

Actually it was Chuck who said that...

I'm really confused about just what it is that you want to do; IMHO the best thing to do with the Corvus (IMI) disk (and maybe the S100 card as well) is to sell it to someone whose system needs it.

And how will a SASI to USB interface let you "access all the rare data stored all over ebay"? What did you have in mind?

Also, direction matters; there are certainly SASI/SCSI-to-MFM bridge boards out there (I've got one or two somewhere) but AFAIK there are no MFM-to-SASI (or anything for that matter) converters (assuming of course that when we say MFM we're all really talking about the ST406/512 interface).

 

[Chuck(G)]

I should add that what I said in context was that the SASI ]u]interface[/u] is little more than a parallel port. What goes between an MFM drive and the SASI interface (i.e. the controller) is a whole 'nother matter...

Sort of like saying that IDE/PATA is little more than a naked ISA bus. True, but there's a lot of logic onboard an IDE drive to get to that interface.

 

[MikeS]

I should add that what I said in context was that the SASI ]u]interface[/u] is little more than a parallel port. What goes between an MFM drive and the SASI interface (i.e. the controller) is a whole 'nother matter...

Sort of like saying that IDE/PATA is little more than a naked ISA bus. True, but there's a lot of logic onboard an IDE drive to get to that interface.

Yeah, there seems to be some confusion about drive interfaces vs. computer interfaces and also the physical vs. the logical aspect of the interfaces...

I wonder if there's a table somewhere listing all the possible combinations, or at least those that actually existed; was there ever an ISA bus controller for a Corvus drive, for example?

 

[Chuck(G)]

Well, I have an Ampex Megastore card here that's SASI and I know that there were ISA SMD adapters. Then there are the converters (MFM-to-SCSi?SASI)...

Which is curious because I'd guess that SMD would have been the logical choice for the S100 community in the early days of S100 systems. Few (other than hard-bitten minicomputer fanatics) in the vintage community are even familiar with SMD.

 

[MikeS]

Well, I have an Ampex Megastore card here that's SASI and I know that there were ISA SMD adapters. Then there are the converters (MFM-to-SCSi?SASI)...

Which is curious because I'd guess that SMD would have been the logical choice for the S100 community in the early days of S100 systems.

Well, as I recall from those days SMD drives were more expensive than the IMI/Corvus drives et al that preceded the (relatively) cheap ST-406s.

But now You're confusing me (easily done): I thought that you usually name these things from the computer point of view? There were certainly converters that took SASI/SCSI from the computer to an ST-506 drive, but not the other way (MFM controller to a SASI/SCSI drive) or this discussion would be largely moot. Is there a convention, i.e "SCSI to MFM" or "MFM to SCSI" when the drive is MFM?

 

[Chuck(G)]

Not that I'm aware of. Sort of like the AT-to-XT keyboard converter discussions. I'm never quite sure which is meant.

But SMD precedes ST-506 by a fair number of years. In 1975, it probably would have been the only common hard disk interface available to a S100 user. SASI didn't come along until 1979. The SA-4000 14" Winchester was 1978. WD made both support devices (WD1050) and board-level products WD1002-MFT for SMD drives.

 

[fibrewire]

I found what I was looking for, now i just need to buy one. A ttl board that makes a select few ST-506/ST-412 drives into SCSI drives.

View attachment bms-100 compatibility.txt

Also ***FREE*** Corvus Systems S-100 board. For whoever needs it.

 

[Chuck(G)]

Good luck with that--you may find that (like the OMTI) the version of "SCSI" is significantly downlevel from what most SCSI controllers will accept.

 

[MikeS]

I found what I was looking for, now i just need to buy one. A ttl board that makes a select few ST-506/ST-412 drives into SCSI drives.
View attachment 5383View attachment 5384View attachment 5382
View attachment 5381

Also ***FREE*** Corvus Systems S-100 board. For whoever needs it.

I could maybe use that since I have a few Corvus drives and S100 systems...

Glad you found what you're looking for; out of all the different things you mentioned (serial<>MFM, Corvus<>Atari, SASI<>USB, SASI<>Atari, SASI<>S100), SASI or SCSI<>MFM was about the only one that you didn't mention ;-)

When you're hunting, aside from that BMS-100 and the OMTI that Chuck mentions, keep an eye out for Xebec; they also made SASI and SCSI to MFM bridge boards.

Good luck!