• Please review our updated Terms and Rules here

AT&T UNIX PC enthusiasts out there?

Teletech

Experienced Member
Joined
Jul 25, 2022
Messages
194
Haha four of them wow! I’ve heard of the expansion box but never seen one, that’s cool you have one. Can’t believe they even made such a device. You’d think 3 slots would suffice. Do you happen to have one of the rare Ethernet cards kicking around? The 1.5MB RAM card, that’s a nice one to have.
The expansion gives you 5 slots but costs one in the CPU. Mine contains two phone cards and I have another two in another machine, I wonder what cool audio shenanigans one could get up to as a musical platform with all that?
No, no ethernet cards.
Somebody really should just make a retro ethernet card for these, and toss some RAM on for good measure. Seems like every other platform has some heavy retrocomputing support but apart from MFM emulators, I don't recall seeing anything for the 7300/3B1.
 

agentb

Experienced Member
Joined
Apr 22, 2021
Messages
323
Location
Philly, USA
Yeah I was recently reading about playing back audio on those Voice Power boards, could be interesting if you could write a little mod tracker type program. There are some pretty proprietary chips on those boards so documentation would likely be lacking, but could be interesting.

A combo RAM / Ethernet card would be amazing. Sourcing the ~99-pin S4BUS connector may be a little tricky but I haven’t looked. @Twylo was recently proposing cloning the Ethernet card which I thought was a great and interesting idea. The schematics are included in the Ethernet Theory of Operation doc:
 

Teletech

Experienced Member
Joined
Jul 25, 2022
Messages
194
Yeah I was recently reading about playing back audio on those Voice Power boards, could be interesting if you could write a little mod tracker type program. There are some pretty proprietary chips on those boards so documentation would likely be lacking, but could be interesting.

A combo RAM / Ethernet card would be amazing. Sourcing the ~99-pin S4BUS connector may be a little tricky but I haven’t looked. @Twylo was recently proposing cloning the Ethernet card which I thought was a great and interesting idea. The schematics are included in the Ethernet Theory of Operation doc:
Outstanding that the schematics exist like that, there is a PROM and a PAL on there, so just cloning the hardware won't get you there unless someone with one of the boards offered to read or offer to someone who could read those devices (assuming they are socketed, if not it's even harder of course).

The connectors are unobtanium... *except* I'm told they are identical to standard VME connectors with one less row of pins. Pretty trivial to make a jig and mill off part of a VME connector if that's the case. I have a CNC mill so could do up a bunch of them. I'll hold one up to a VME connector in the next day or so and see if that's true.

Also, tripped over this guide on the bus: https://www.philpem.me.uk/_media/code/3b1emu/trm/3b1_specs.pdf
 

agentb

Experienced Member
Joined
Apr 22, 2021
Messages
323
Location
Philly, USA
I’m sure we could get the PROM and PAL’s read. But sourcing that 99-pin port does sound tricky. Interesting about the VME connector. I knew that S4BUS spec was kicking around somewhere, fortunately there’s some decent tech info around on the UNIX PC hardware.
 

Teletech

Experienced Member
Joined
Jul 25, 2022
Messages
194
I’m sure we could get the PROM and PAL’s read. But sourcing that 99-pin port does sound tricky. Interesting about the VME connector. I knew that S4BUS spec was kicking around somewhere, fortunately there’s some decent tech info around on the UNIX PC hardware.
Well, darn. Turns out I was half right, the S4bus connector is identical to a VME connector with one ADDITIONAL pin in length. That's a much harder job obviously. Still, I'd tool up to make a spliced VME connector if we had a board to put it on.
The other option might be to shift the connector so you give up three pins on one end. Looking at the spec, one side is address pins, but the other side is +/-12V.
Looking at the Ethernet board schematics somewhat carefully, I don't see the 12V being used, so we should be able to just use a VME connector!
It makes me sad that only 20 address pins are present at the expansion bays. It also makes me wonder if anyone ever tried one of the daughterboards where you plug a 68020 (and sometimes optional 68881 and ram and/or cache) into the board and then the board into the 68000 socket? They exist for Amiga in a wide variety I know, any reason why one wouldn't work for the 7300?
Space is pretty tight and I can imagine one might possibly have to modify the upper sheetmetal, but how cool would it be to have a FPU, cache, and 8+MB of high-speed ram?
Speaking of modernization, what luck have folks had with the MFM drive emulators? Obviously that was a huge issue with the original machines.
 

agentb

Experienced Member
Joined
Apr 22, 2021
Messages
323
Location
Philly, USA
I found the part number on the original connector, AMP 2-532431-0. Sure enough, one column longer to get the 99 pins vs VME 96 pins. That would be great if a VME connector could work.

The CPU is 68010 (for the virtual memory support) so doubtful if one of those 68020 daughterboards would work, but I don't know much about them or how exactly they work. Sure wouldn't mind speeding up a UNIX PC if it was possible. There was actually a plan to include a 68881 socket at one point on the motherboard -- or a later incarnation -- but that never came to be. I think there's a 68881 ref in some of the headers.

I have one of David Gesswein's MFM emulators in my machine, works great and gives me a lot of confidence versus having a MFM drive in there. I also have a gotek hooked up. But I do want to put an original floppy back in as I have some 7300 backup disks I want to go through. I'd also like to get a 720k floppy to hook up, just because i think it would be fun to have a UNIX PC with a 3.5" drive, apparently fairly popular to do back in the day.
 

Teletech

Experienced Member
Joined
Jul 25, 2022
Messages
194
I found the part number on the original connector, AMP 2-532431-0. Sure enough, one column longer to get the 99 pins vs VME 96 pins. That would be great if a VME connector could work.

The CPU is 68010 (for the virtual memory support) so doubtful if one of those 68020 daughterboards would work, but I don't know much about them or how exactly they work. Sure wouldn't mind speeding up a UNIX PC if it was possible. There was actually a plan to include a 68881 socket at one point on the motherboard -- or a later incarnation -- but that never came to be. I think there's a 68881 ref in some of the headers.

I have one of David Gesswein's MFM emulators in my machine, works great and gives me a lot of confidence versus having a MFM drive in there. I also have a gotek hooked up. But I do want to put an original floppy back in as I have some 7300 backup disks I want to go through. I'd also like to get a 720k floppy to hook up, just because i think it would be fun to have a UNIX PC with a 3.5" drive, apparently fairly popular to do back in the day.
Oops, I was looking at a VME card with a 68000 today and hadn't opened a UNIX PC in a long time, so had forgotten it was a 010.
That makes it less likely that simply using an Amiga upgrade would work, but still not unreasonable to imagine a 020 + FPU upgrade board could be made considering all the retrocomputing work in the world today. I guess it's a question of if anybody has the time, the skills, and the motivation. How many UNIX PCs are still out there is one question and how much would one being faster and having more memory matter is another. I guess the ethernet card would be a better bet. I wonder what would happen if someone fed the chip layout and schematics that we do have to an autorouter?

Are you using the MFM emulator as a 67MB drive, or did you go bigger? Makes me wish I had an original wedge case, but all mine are humps or hump-added. I might strip the hump off one and see how close I can get to the original look.

In other news, I think I might have found a partial fifth unit. This is getting out of hand! I'll check storage and see if the rest of it is in there.
So, it's dumb for me to own any of these really, but to own more than two is just silly. If more people own them, that will mean more interest in the platform and that's a good thing. So, before I drag a couple to VCF, any help about what they are worth these days?

So far I have (confirmed)
7300 with 1/1.5MB ram, 40MBdrive
3b1 2MB ram,
3b1, no details
3b1, no details
4 phone cards
1 ram/serial card (1.5MB)
1 expansion chassis
1 taps interface card
1 DOS card
2 keyboards
2 mice
1 set of manuals, install media

(suspected)
3b1, 2 keyboards, mouse
1 ram/ serial card
1 starlink card
 
Last edited:

djg

Experienced Member
Joined
Oct 24, 2008
Messages
183
Location
MD
Well, darn. Turns out I was half right, the S4bus connector is identical to a VME connector with one ADDITIONAL pin in length. That's a much harder job obviously. Still, I'd tool up to make a spliced VME connector if we had a board to put it on.
Can get 120 pins at reasonable price. https://www.ebay.com/itm/274789113215?hash=item3ffab51d7f:g:lVkAAOSwyyRglX1G
I'd go for a couple cut down for future possible projects. Not sure I can cut cleanly enough to not destroy the last contacts.

So, before I drag a couple to VCF, any help about what they are worth these days?

Last sale.
https://www.ebay.com/itm/2037854790...=true&nordt=true&rt=nc&_trksid=p2047675.l2557
 

Teletech

Experienced Member
Joined
Jul 25, 2022
Messages
194
Good find. I could fix
Can get 120 pins at reasonable price. https://www.ebay.com/itm/274789113215?hash=item3ffab51d7f:g:lVkAAOSwyyRglX1G
I'd go for a couple cut down for future possible projects. Not sure I can cut cleanly enough to not destroy the last contacts.
Good find there. $58/ea is a bit steep, but not bad as a raw material for unobtanium. I think I'd just as soon use a VME and loose the 12V for the purpose of RAM and ethernet.
I do have a CNC mill, so am happy to try to do a good clean cut job for them if someone wants to send one my way.

Thanks for the listing link, $750 with no keyboard, mouse, or cards and no promise of a good HD or MB at first glance seems spendy, but in context of what were $79 mouser rifles at Big-5 20 years ago selling for $2000 today, or the fact I paid $200 for one chrome trim piece for my Datsun recently, I guess it's not bad at all.
 

agentb

Experienced Member
Joined
Apr 22, 2021
Messages
323
Location
Philly, USA
That listing was for 4 connectors, so ~$15/ea but yeah still a little pricey. If you got the alignment right, and they weren’t too wide, which they probably are, maybe could just use that 120-pin as-is. But good there may be some options. I agree, the Ethernet (or more RAM) seem like the best options for a modern project.

Can’t believe you found a fifth! I’d say $500+ is the proper ballpark for price. One just sold near me for $355 (non-working). And the guy has another working listed for $500. Got them from his deceased neighbor.
That guy in Pittsburgh was trying to sell for $750 for many months.

I definitely prefer the proper wedge also. Don’t love the hump. But 3b1’s sometimes have 2MB RAM which is nice. I’m considering taking my 3b1 motherboard and putting in my 7300 if that’s compatible. But don’t look forward to disassembling two machines.

I went with the 67MB option as there was a pre-made drive image I used from
David Gesswein that he’d made for the VCF museum’s 7300. Worked great! If you want a bigger drive, I think you might need to do the WD2010 swap and add the extra head select, I can’t remember off-hand what’s required.
 

Teletech

Experienced Member
Joined
Jul 25, 2022
Messages
194
That listing was for 4 connectors, so ~$15/ea but yeah still a little pricey. If you got the alignment right, and they weren’t too wide, which they probably are, maybe could just use that 120-pin as-is. But good there may be some options. I agree, the Ethernet (or more RAM) seem like the best options for a modern project.

Can’t believe you found a fifth! I’d say $500+ is the proper ballpark for price. One just sold near me for $355 (non-working). And the guy has another working listed for $500. Got them from his deceased neighbor.
That guy in Pittsburgh was trying to sell for $750 for many months.

I definitely prefer the proper wedge also. Don’t love the hump. But 3b1’s sometimes have 2MB RAM which is nice. I’m considering taking my 3b1 motherboard and putting in my 7300 if that’s compatible. But don’t look forward to disassembling two machines.

I went with the 67MB option as there was a pre-made drive image I used from
David Gesswein that he’d made for the VCF museum’s 7300. Worked great! If you want a bigger drive, I think you might need to do the WD2010 swap and add the extra head select, I can’t remember off-hand what’s required.
I missed that, ~$15/ea is entirely reasonable, but in this case where the 12V isn't important I think the reduction in labor of modifying a connector extensively is the win. The 120s *are* too long since there is a shield around the connector.
Good commentary on price, I've been away from it all for a long time. Long enough the "this machine boots and runs fine -may 2006" label is rather faded...

You don't have to take the whole machine apart too badly to get to a MB for a swap, but yeah it's a pain.
I'm planning for a restored wedge with a fully populated MB. I've read that the MB RAM and expansion RAM can coexist so you could in theory get 4MB, is this correct?
I guess the other questions about RAM and HDD size, are so what? That is, would more memory speed things up for the normal use the machine is going to get and is there enough software that 67MB is a serious constraint? I suppose if one were going to fool with the audio boards that could make a lot of data really quickly, but with no web browser, crude mono video, and small old software 67MB might be fine?
 

agentb

Experienced Member
Joined
Apr 22, 2021
Messages
323
Location
Philly, USA
Maxed wedge is the way to go in my opinion. Yes 4MB is the max addressable. I believe to get that you would need to do 2MB on the motherboard and 2MB from the expansion memory. Probably could do a serial combo board with 1.5MB and another RAM board with 512k. Or two 1MB combo boards. Honestly I think 1MB is likely plenty for regular use of the system. 512KB can present problems I believe with the later 3.51 OS. For compilation, more than 1MB probably would be helpful. I haven’t pushed the system yet so not sure where the limitations will be - likely the hard drive speed and CPU speed. 67MB for the HD should be fine. OS is capped to 1024 cylinders. And h/w max of 8 heads. This gets you to the 67MB. There is a mod to get 16 heads but I don’t think worth it.

I don’t have skills with KiCad yet so unfortunately can’t do much on the Ethernet card front but sounds like a great project.
 

agentb

Experienced Member
Joined
Apr 22, 2021
Messages
323
Location
Philly, USA
OS limit is 1400. Controller chip needs to be swapped to go above 1024.
Ahh yes, that’s what it is! Thanks for the reminder, it’s been awhile since I’ve looked at this. So the WD2010 swap let’s you go to the 1400 cylinders.
 

NeXT

Veteran Member
Joined
Oct 22, 2008
Messages
7,088
Location
Kamloops, BC, Canada
They seem like neat early Unix machines with an Xwindow display but while not as expensive as a BLIT they're still pretty expensive.
 

agentb

Experienced Member
Joined
Apr 22, 2021
Messages
323
Location
Philly, USA

jfloren

Member
Joined
Jul 12, 2022
Messages
14
Location
San Francisco, California
Sometimes I wish it was X, but as far as I know, it’s a one-off custom gui for the UNIX PC. There is an MGR port kicking around which is an alternative gui that can be used. I need to spend some more time playing around with MGR. Some more info specific to MGR on the 7300 here: https://www.tuhs.org/Usenet/comp.sys.3b1/1991-June/000340.html
MGR sure looks neat. (reminds me of w9wm window manager, which I'm currently using) That page says:

> If you would like to hack MGR, one nice thing to do would to use the stub libbitblit and write calls to the Linux fb device or use something similar (SDL, perhaps?). This way, MGR could live again and this time on modern graphics hardware. If you pick this up, please notify me. It would be a nice hack.

It's shockingly easy to use Linux fbdev, so that would be quite achievable.

I have never done X programming, but another option could be to make it run in an X window, translating libbitblit calls to X draw events.

The fact that they mention "libbitblit" makes me suspect that the underlying calls could be reasonably compatible with Plan9Port's draw code, which is used to provide Plan 9-like drawing functions to programs running on X.
 
Last edited:

Teletech

Experienced Member
Joined
Jul 25, 2022
Messages
194
OK, so it boots, but...
Backing up slightly, I dragged a pair of 3b1s off the shelf, hosed them down, and decided since the P/S was a switcher, that I was as likely to damage stuff slowly bringing it up as going for it. So, switching them on, the second one has a pattern of lines on the screen, so video works and the video controller is doing something, but there it ends.
The first machine I tried booted right up and seems very happy, sadly I have no password for this machine. So, how does one hack one of these?
I assume if I had a boot floppy I could log in as root and mount the HDD to edit the password file? I can try my other machines and see if any of them still boot, but that's for another day (or more likely week).
Any chance there is an interactive boot mode I can use to gain root?
 

agentb

Experienced Member
Joined
Apr 22, 2021
Messages
323
Location
Philly, USA
Great that one machine booted up! I have a similar problem right now with a 3b1 turning on and displaying a sorta-lined pattern. It booted once or twice prior but now just get the pattern on the screen and no further advancing. Will have to take apart and check power first I’m thinking.

In terms of hacking in, I have an old post suggesting to boot from floppy. Boot and then put the “floppy disk file system”. Then you will get prompted if you want to proceed, or if you want to retain files, something like that. Hit DEL or Shift-DEL and you should get a shell prompt. HD should be mounted at /mnt so can then edit /mnt/etc/passwd - I haven’t tried this but sounds sensible.
 
Top