Tevian wrote on 2025-09-19, 20:23:

As I mentioned in the DM, some of the values are missing in the iBom file as well. For instance, for the voltage status LEDs, yo […]
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As I mentioned in the DM, some of the values are missing in the iBom file as well. For instance, for the voltage status LEDs, you'll have to choose the values for each voltage based on what 0603 LED you buy. I can give you all the values I choose, but if you buy a different common 0603 LED, you might need different values. It's not critical, though. I'll post them if you really need them for reference... I'm attaching the iBom file here as well. You might have missed that I sent it earlier in the DM.

I purchased another PC104+ board. I got a PC104-P3-90C. It's a Pentium 3 system and I'm eager to test it. It came with no cabling, and I see no manual online for it. I was luckily able to find one pic that shows the connector functions, but I'll have to reverse engineer the pinouts. That could take a while. 😬

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Hi Tevian,

Any luck tracing out and reverse-engineering the pinouts on that PC104-P3-90C yet? Those proprietary, high-density multi-pin internal connectors Toronto MicroElectronics used are notoriously brutal to decipher without a factory manual. I have the sister board from that exact same TME lineage (the 1.2 GHz, PC104-P3-12C variant), and tracking down the functional mapping logic for their custom pin headers has been quite the scavenger hunt. Did you manage to fully map the VGA video signals and keyboard lines out to a custom breakout cable, or are you still probing the traces with a multimeter to verify ground planes and voltage pathways? If you've made any progress or have sketches of the pin configuration layout, I'd love to see what you found! It would save a ton of trial-and-error on these obscure industrial modules.

Sorry just seeing this. BTW are you also messaging me on eBay?

I did get the VGA working, but I shelved when I couldn't overcome the BIOS issues. The unit refuses to boot and I'm left with the odd POST screen and the slow RAM count. That was a while ago... I was using jumpers and I may have taken a pic but I need to check.

I'm away from the bench... I had to cables, had to use meter and scope with trial and error. I did find a pic that pointed to which section was responsible for what. That's how I found the keyboard and mouse port.

Tevian wrote on 2026-07-24, 04:09:

Sorry just seeing this. BTW are you also messaging me on eBay?

I did get the VGA working, but I shelved when I couldn't overcome the BIOS issues. The unit refuses to boot and I'm left with the odd POST screen and the slow RAM count. That was a while ago... I was using jumpers and I may have taken a pic but I need to check.

Hey Tevian,

Yeah, that was me on eBay. I'm currently away working offshore so no rush, if you have any information on the pinout (VGA, keyboard and mouse) it would be very appreciated. if not I'll have to go down the same route you did, trial and error. fun and games.

Do you have more of these bords available?

Hi Tevian, I just discovered this thread, what an amazing project!
I recently published a short review of the BOSER HS-6251: [https://youtu.be/DfVFPjvRDhc?si=FcM1CGcyuMtkvW1-](https://youtu.be/DfVFPjvRDhc?si=FcM1CGcyuMtkvW1-)

I have a few SBCs myself, including an Allen-Bradley board that I can’t use with standard PISA backplanes.
What’s the latest version of your board, and is there any way to obtain one?
Great work!

Dodobird wrote on 2026-09-24, 16:20:

Hi Tevian, I just discovered this thread, what an amazing project! I recently published a short review of the BOSER HS-6251: [ht […]
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Hi Tevian, I just discovered this thread, what an amazing project!
I recently published a short review of the BOSER HS-6251: [https://youtu.be/DfVFPjvRDhc?si=FcM1CGcyuMtkvW1-](https://youtu.be/DfVFPjvRDhc?si=FcM1CGcyuMtkvW1-)

I have a few SBCs myself, including an Allen-Bradley board that I can’t use with standard PISA backplanes.
What’s the latest version of your board, and is there any way to obtain one?
Great work!

Sorry for the delay!

Thanks again for reaching out. I hope the backplane works out!

Cool video too!

About the versions, the V1.0 was the most recent. PCB design is just a hobby and not my primary source of income. That being said, I do try to make my hobbies pay for themselves. Of the small batch of backplanes I've made, I've now only sold 5 in total.

After some feedback I've gotten, I have a handful of ideas for a V1.1. I think I would ditch the PCI mapper card in favor of a jumper block. The card style does work, but the configurations are semi-permanent because you have to solder the SMD resistors.

Also, someone that purchased a backplane, (it was a few months ago and can't remember...) tested the Allan Bradley card a bit more and found some instability with my implementation in re-creating the proprietary backplane CPU power. In my testing, I ran into an issue that I assumed was a BIOS problem as my onboard sound chip would fail to recognize. He found that skipping the 8 power pin jumpers and simply using the AUX power to feed the Allan Bradley cards direct solved this.

This is baffling and I went through the PCB very close and could see no obvious problems. So, one thing I might do is redesign and the let those 8 pin float on both types, except the reset pin for PCISA that also claim one of those pins, and just rely on an AUX power cable for Allen Bradley cards. (BTW, if you were the one that figured this out, please reply and take credit!).

The instability seemed to only be with my sound chip implementation and the Allen Bradley SBCs. All other types I tested were rock solid!

Super curious to see what you put together. And yes, Voodoo 2's can come in small packages! 😉

Just got my board from you on eBay today @Tevian, EXCELLENT build quality, and thanks again for the surprise. I'll upload pics once I get this all assembled in the case with the SBC!

Xardion wrote on Yesterday, 20:12:

Just got my board from you on eBay today @Tevian, EXCELLENT build quality, and thanks again for the surprise. I'll upload pics once I get this all assembled in the case with the SBC!

Oh... Great. I got the things backwards, the above message was aimed to you. Thx for the purchase, and I hope things work out. Send pics.

Tevian wrote on Yesterday, 21:05:

Oh... Great. I got the things backwards, the above message was aimed to you. Thx for the purchase, and I hope things work out. Send pics.

HEH I had a suspicion! Interestingly, I've been talking to @Dodobird over e-mail as well (should've known he was on Vogons), as it was his video that prompted me to buy one of those Boser SBCs, and ultimately to buy a Backwards backplane.

So here's a dry fit in the case I'm using. That PCI card is just a 3Com card I used to make sure the slot->rear spacing was gonna work out, and it's pretty good. I had to bend a slight forward angle on the card bracket to avoid putting too much torque on the board when screwing the card down. Not much though, just a degree or two. That 5V top layer makes me SLIGHTLY nervous about the screws, even with the plastic washers. I might put just a tiny strip of teflon thread sealer tape (just the thickness of the PCB+washer) around the top of the threads, just to make SURE that a thread edge doesn't make contact with that live 5V layer should the board need to be shifted around (or just shifts on its own due to gravity, etc). Just a little peace of mind. Fits great though, kinda a perfect pair with the industrial fanless mini ITX board I have in there (running FreeBSD on that one).

Also... something I've read but I wasn't sure if it was 100% true, especially on the Backwards board: are the brown PISA slots also usable as an ISA slot? Apparently that's how it supposedly designed (ISA on the top row edge connectors, PCI on the bottom row).

I'd kinda like to stick a PicoGUS in there, right next to the SBC, and doing a careful zoom in to get the PicoGUS in my hand to scale to the SBC on the scree, it DOES look like the ISA connector perfectly lines up with the upper row of the PISA connector. Also, luckily the PicoGUS is a pretty short 8-bit card, so clearing the CPU and ram won't be an issue. Tucking the floppy and parallel connetors behind it will probably suck. Literally the ONLY issue I can see being a problem is that it is literally the shortest possible 8-bit ISA card. There's no bit of card hanging over the rear edge of the connector, so it would be floating unsupported on the back inside a slot with active PCI lines waiting for trouble just below it. I think what I'd do is cut a bit of PCB off a dead card with my bandsaw, line it up with the bottom of the front edge, and glue it to the back corner of the card for support.

Definitely looks like it should work.

Oh, I just realized, there are keys underneath the edge there, you can't accidentally insert an unsupported ISA card in there too far. DERP.

Xardion wrote on Today, 02:05:

Oh, I just realized, there are keys underneath the edge there, you can't accidentally insert an unsupported ISA card in there too far. DERP.

Yes, the SBC slots are backwards compatible with ISA cards, there's no issues there, but the same caution about insertion and removal still stand. Those SBC slots are fragile!

As for the 5V plane, not to worry too much. The screw pads themselves are grounded! I made sure of that. The only issue is using larger head screws that might hang over the ground pad. That's why I included the washers. The screw are safe by themselves but close. The washers are just for extra safety.

Tevian wrote on Today, 03:24:

As for the 5V plane, not to worry too much. The screw pads themselves are grounded! I made sure of that. The only issue is using larger head screws that might hang over the ground pad. That's why I included the washers. The screw are safe by themselves but close. The washers are just for extra safety.

OHHHH, hahaha, alrighty. I was worried for nothing then, I am using the supplied screws, and they fit well within the pads, so no worries. I see what you mean though, no matter which position you're able to use, there's always at least two of the mounting holes that have a component pad pretty damn close to those ground pads, and a normal mounting screw (especially the ones for the 6-32 standard brass standoffs most ATX cases use) would absolutely overhang and probably touch something. But the ones you included fit well within the pads, and with how I have it mounted, the only risk at all is down on the sound card/ATX power end. But I've got leagues before anything would touch.