ajacocks wrote on 2025-07-28, 13:01:

Thanks for all the hard work @Tevian! I just bought one of your backplanes.

- Alex

🤗 Thanks! I see that and will get it shipped tomorrow. I really hope you like it. I'll send a few printouts along about the correct screws I include. And also, remember to extra cautious with those EISA slots! The pins are very fragile.

Also, I'd be curious of what model SBC you're going to use and I'll be here to answer any questions.

Tevian wrote on 2025-07-28, 12:39:

The link for the adaptor is broken, so I can't see it. However, if it's a simple PC/104 to ISA, then it should work just fine. A […]
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mbandalauk wrote on 2025-07-13, 09:19:

I need one! I noticed you added a wavetable at the back of your backplane — is that an RPi Zero on an MT-32 Pi adapter? Did you […]
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Tevian wrote on 2025-01-27, 08:38:

The attachment Backwards_V1.0.jpg is no longer available

I need one! I noticed you added a wavetable at the back of your backplane — is that an RPi Zero on an MT-32 Pi adapter? Did you design that yourself, or is it something that’s available to buy?

I have another question: I own a PC/104 PC104 PCM-3370 along with a slot adapter for it — the adapter is for ISA, of course. I think I could easily use your backplane with it. The PCM-3370 also supports the PC/104+ standard, which includes the 120-pin PCI connector. I was thinking about making an extension from that connector to one of the PCI slots on your backplane so I could use both the ISA and PCI capabilities of the PCM-3370.

Do you think that could work?

The link for the adaptor is broken, so I can't see it. However, if it's a simple PC/104 to ISA, then it should work just fine. An adaptor to the PCI slots would work as well, I just don't know of any. An adaptor card with the EISA edge connector would be ideal since the PCI pins are there, but one would have to be made, I think. A flex ribbon connector to the PCI slots would also work, though... But, one would have to be made. If you do make such a connector, I'd be curious to see it.

I do have the Backplanes up on eBay, https://www.ebay.com/usr/tevianbusselle.

As far as the wavetable card, yes I did design them. It's a simple carrier card for a Rasp Pi Zero 2 with the DAC installed. I don't have them on eBay at the moment and only have a few prototypes handy. I still haven't ordered a final version of the PCB, and I'm not sure what kind of demand there is for it.

The attachment wavee.jpg is no longer available

Hi Tevian – thanks for your reply.
You're right, I couldn't find any off-the-shelf PC/104+ to PCISA adapter—it seems one would need to be custom-made. I wonder if there's a reference PCB footprint available with a PCISA edge connector that could serve as a starting point for a design, especially since both PCI and ISA interfaces are present on the PCM-3370.

I’d really like to purchase one of your backplanes, but eBay shows that shipping to the UK isn’t available. Is there any way around this?

Also, your wavetable card looks excellent. I think it's a great and affordable alternative to Serdashop's MacCake—not everyone needs an OLED screen. I'd be very interested in purchasing one as well, if it's available.

Thanks again!

"I couldn't find any off-the-shelf PC/104+ to PCISA adapter"

When I find some free time, I could generate an EISA edge connector footprint. 😉

Making a full adapter card wouldn't be super hard as long as I can find an accurate technical drawing for the headers. I don't have any PC104 cards on hand.

I'll DM you about the backplane.

https://www.google.com/search?sca_esv=d9deabf … ih=705&dpr=2.63

I see many isa/pc104 adapters.
What specifically are you after?

myne wrote on 2025-07-30, 03:40:

https://www.google.com/search?sca_esv=d9deabf … ih=705&dpr=2.63

I see many isa/pc104 adapters.
What specifically are you after?

Yes, PC/104 to ISA adapters are quite common, and as Tevian mentioned above, my PCM-3370 will work fine with one of those when used with his backplane.

However, I'm specifically looking for a PC/104+ (note the plus) to PCISA adapter with an EISA edge connector—see the specification of PC/104+ here:
https://pc104.org/hardware-specifications/pc104-plus/

Adapters with EISA connectors for PC/104+ boards, which include both ISA and PCI, are virtually impossible to find as far as I know. That’s why we believe it might be worth designing one. PC/104+ boards are still relatively common, and many of them are quite capable—making them especially attractive for retro gaming and embedded projects.

Tevian wrote on 2025-07-30, 02:17:

"I couldn't find any off-the-shelf PC/104+ to PCISA adapter" […]
Show full quote

"I couldn't find any off-the-shelf PC/104+ to PCISA adapter"

When I find some free time, I could generate an EISA edge connector footprint. 😉

Making a full adapter card wouldn't be super hard as long as I can find an accurate technical drawing for the headers. I don't have any PC104 cards on hand.

I'll DM you about the backplane.

Thanks, I’ll reply shortly. Building the full adapter should be almost too easy for you, considering what you've already accomplished with your previous designs!

Following up on my earlier post, it would be fantastic to see an adapter with an EISA connector that also includes some essential ports. For example, the simpler PC/104-to-ISA adapter that I have (shown in the image below) has VGA, PS/2, and even a serial port—features that are incredibly useful. Many PC/104 and PC/104+ boards lack physical connectors and rely on pigtails for I/O, so having those ports built into the adapter would be a huge convenience. It would be almost like having a regular half-size EISA board!

mbandalauk wrote on 2025-07-30, 04:16:

Yes, PC/104 to ISA adapters are quite common, and as Tevian mentioned above, my PCM-3370 will work fine with one of those when u […]
Show full quote

myne wrote on 2025-07-30, 03:40:

https://www.google.com/search?sca_esv=d9deabf … ih=705&dpr=2.63

I see many isa/pc104 adapters.
What specifically are you after?

Yes, PC/104 to ISA adapters are quite common, and as Tevian mentioned above, my PCM-3370 will work fine with one of those when used with his backplane.

However, I'm specifically looking for a PC/104+ (note the plus) to PCISA adapter with an EISA edge connector—see the specification of PC/104+ here:
https://pc104.org/hardware-specifications/pc104-plus/

Adapters with EISA connectors for PC/104+ boards, which include both ISA and PCI, are virtually impossible to find as far as I know. That’s why we believe it might be worth designing one. PC/104+ boards are still relatively common, and many of them are quite capable—making them especially attractive for retro gaming and embedded projects.

Ah. Right.
One of those things I've read about occasionally, but never seen.
Always got confused thinking 8 bit =isa, 16b =eisa.
Thought 32bit was mca.

Anyway. Carry on.

mbandalauk wrote on 2025-07-30, 04:41:

Tevian wrote on 2025-07-30, 02:17:

"I couldn't find any off-the-shelf PC/104+ to PCISA adapter" […]
Show full quote

"I couldn't find any off-the-shelf PC/104+ to PCISA adapter"

When I find some free time, I could generate an EISA edge connector footprint. 😉

Making a full adapter card wouldn't be super hard as long as I can find an accurate technical drawing for the headers. I don't have any PC104 cards on hand.

I'll DM you about the backplane.

Thanks, I’ll reply shortly. Building the full adapter should be almost too easy for you, considering what you've already accomplished with your previous designs!

Following up on my earlier post, it would be fantastic to see an adapter with an EISA connector that also includes some essential ports. For example, the simpler PC/104-to-ISA adapter that I have (shown in the image below) has VGA, PS/2, and even a serial port—features that are incredibly useful. Many PC/104 and PC/104+ boards lack physical connectors and rely on pigtails for I/O, so having those ports built into the adapter would be a huge convenience. It would be almost like having a regular half-size EISA board!

Okay... https://www.ebay.com/itm/136242586542 --> $220 + $5. (Backplane + a working prototype of the wavetable card + $5 shipping)

Try this one! I turned on UK shipping for this individual listing and will use the eBay International Shipping Program. Never done this before, but I guess I can use their shipping hub to ship locally, then eBay takes care of the shipping to the UK.

I only have one working prototype, and you're welcome to it since you were interested. In the near future, I'll get those finalized and list them on eBay proper. If you can finally message on PM by the time you see this, send me a message there. I can't give my email over eBay messaging!

mbandalauk wrote on 2025-07-30, 04:16:

Yes, PC/104 to ISA adapters are quite common, and as Tevian mentioned above, my PCM-3370 will work fine with one of those when u […]
Show full quote

myne wrote on 2025-07-30, 03:40:

https://www.google.com/search?sca_esv=d9deabf … ih=705&dpr=2.63

I see many isa/pc104 adapters.
What specifically are you after?

Yes, PC/104 to ISA adapters are quite common, and as Tevian mentioned above, my PCM-3370 will work fine with one of those when used with his backplane.

However, I'm specifically looking for a PC/104+ (note the plus) to PCISA adapter with an EISA edge connector—see the specification of PC/104+ here:
https://pc104.org/hardware-specifications/pc104-plus/

Adapters with EISA connectors for PC/104+ boards, which include both ISA and PCI, are virtually impossible to find as far as I know. That’s why we believe it might be worth designing one. PC/104+ boards are still relatively common, and many of them are quite capable—making them especially attractive for retro gaming and embedded projects.

Okay... I'm looking into it. It shouldn't be too complicated to make an adaptor card for PC/104+. The only issue, I don't have any PC/104 cards on hand. The technical drawings in the spec sheet look good, so it "should" work. Although, for testing, I'd probably have to get one. 😅

There is an issue of orientation. In the standard versions, with the ISA connector along the bottom edge, all the pins are crossed.

A rotation of 90 degrees clockwise makes the connections a bit more straightforward. This makes the CF card slot point up and should be fine

The next issue is the baffle. A custom PC CARD baffle might not be worth it, so I'm looking for an off-the-shelf one from AliExpress, but I'm not finding one that has all the ports I'd like. A 3D printed one would technically work, but a metal bracket off-the-shelf would be preferred.

Tevian wrote on 2025-08-03, 11:48:

Okay... I'm looking into it. It shouldn't be too complicated to make an adaptor card for PC/104+. The only issue, I don't have a […]
Show full quote

mbandalauk wrote on 2025-07-30, 04:16:

Yes, PC/104 to ISA adapters are quite common, and as Tevian mentioned above, my PCM-3370 will work fine with one of those when u […]
Show full quote

myne wrote on 2025-07-30, 03:40:

https://www.google.com/search?sca_esv=d9deabf … ih=705&dpr=2.63

I see many isa/pc104 adapters.
What specifically are you after?

Yes, PC/104 to ISA adapters are quite common, and as Tevian mentioned above, my PCM-3370 will work fine with one of those when used with his backplane.

However, I'm specifically looking for a PC/104+ (note the plus) to PCISA adapter with an EISA edge connector—see the specification of PC/104+ here:
https://pc104.org/hardware-specifications/pc104-plus/

Adapters with EISA connectors for PC/104+ boards, which include both ISA and PCI, are virtually impossible to find as far as I know. That’s why we believe it might be worth designing one. PC/104+ boards are still relatively common, and many of them are quite capable—making them especially attractive for retro gaming and embedded projects.

Okay... I'm looking into it. It shouldn't be too complicated to make an adaptor card for PC/104+. The only issue, I don't have any PC/104 cards on hand. The technical drawings in the spec sheet look good, so it "should" work. Although, for testing, I'd probably have to get one. 😅

The attachment Screenshot 2025-08-03 042145.png is no longer available

There is an issue of orientation. In the standard versions, with the ISA connector along the bottom edge, all the pins are crossed.

The attachment Screenshot 2025-08-03 043610.png is no longer available

A rotation of 90 degrees clockwise makes the connections a bit more straightforward. This makes the CF card slot point up and should be fine

The attachment Screenshot 2025-08-03 043754.png is no longer available

The next issue is the baffle. A custom PC CARD baffle might not be worth it, so I'm looking for an off-the-shelf one from AliExpress, but I'm not finding one that has all the ports I'd like. A 3D printed one would technically work, but a metal bracket off-the-shelf would be preferred.

The attachment Screenshot 2025-08-03 044450.png is no longer available

The attachment Screenshot 2025-08-03 044513.png is no longer available

Another fantastic contribution to the community! You're right—you’ll likely need a PC/104+ board for proper testing. The 90-degree rotated version looks excellent. I believe my PCM-3370 would fit nicely, and conveniently, the CF slot would face upwards. However, there might be limited clearance between the heatsink and the EISA connector—see the PCM-3370 board below for reference.

I'd be happy to send you mine for testing if that helps. I’m sure we could work something out, though I’m based in the UK, and unfortunately, shipping costs and potential import duties do make things a bit tricky.

Regarding the off-the-shelf bracket, yes, it will definitely be difficult to find one that's ideal. The PCM-3370 has a mix of ports that could potentially be broken out through the bracket. It includes a combined PS/2 mouse/keyboard connector, two USB ports, a VGA output, an Ethernet port, an LPT port, and four serial ports.

Which connectors would you like to have on the bracket? Personally, I’d vote for at least VGA, Ethernet, and PS/2. The USB ports on my PCM-3370 are actually routed to a separate bracket—similar to the one shown below.

Are you 1000% sure you didn't accidentally flip the pin numbers on one of those?

I ask because we collectively at one point or another completely ballsed up an isa footprint in the dISAppointment thread

myne wrote on Yesterday, 01:11:

Are you 1000% sure you didn't accidentally flip the pin numbers on one of those?

I ask because we collectively at one point or another completely ballsed up an isa footprint in the dISAppointment thread

Yes, good eye! I was wondering about this as well, but after some searching and probing my PCISA-C400R-RS-R20 SBC that has a PC/104 socket, I believe this is the correct pinout!

Here's an ISA adaptor card that has the PC/104 ISA socket "inverted" on the top side, which is 180 degrees from my PCISA-C400R SBC. Note the visible traces are all straight! On the others, note the complex routing, or backside sockets. I don't know if there was an industry standard way to mount these on adaptor cards, but I've verified the grounds and voltage rails all match on my mockup to my PCISA-C400R SBC.

Stupid question.
Was PCI an electrically compatible spinoff of EISA?
Because I'm wondering how exactly you're going to mate a pc104+ PCI card to an EISA adapter.
I know some SBCs reused the EISA connector for ISA+PCI (as pictured above), but AFIK they weren't EISA compatible.

Never mind. I forgot what thread I was in. Makes sense now.

This should help. Pg a2, b2, b3
https://pc104.org/wp-content/uploads/2015/02/ … _Plus_v2_32.pdf

myne wrote on Yesterday, 06:41:

Stupid question. Was PCI an electrically compatible spinoff of EISA? Because I'm wondering how exactly you're going to mate a pc […]
Show full quote

Stupid question.
Was PCI an electrically compatible spinoff of EISA?
Because I'm wondering how exactly you're going to mate a pc104+ PCI card to an EISA adapter.
I know some SBCs reused the EISA connector for ISA+PCI, but AFIK they weren't EISA compatible.

This should help
https://pc104.org/wp-content/uploads/2015/02/ … _Plus_v2_32.pdf

Yes, that's the datasheet I'm going off.

No, EISA is still a special case standard for (Enhanced Industry Standard Architecture) cards only. The EISA slot on EISA-compatible motherboards was only ISA backward compatible! The extra pins on these cards and motherboards were for the EISA spec only!

Now, PISA or PCISA spec'd SBCs used the physical EISA-style slot for the pin count. The PISA/PCISA/Rockwell use of the EISA slot still had all ISA pinout on the top row, but had the PCI pinout on the bottom row, which is not compatible with the EISA spec.

So, this adaptor card, if I go through with it, would only work in PISA/PCISA backplanes, as well as my own, which is what I'm mirroring. One issue with doing it this way for compatibility with my backplane is the loss of PCI3 and PCI4 addressing. This is because on my backplane, those pins are absent in favor of compatibility with the Allen Bradley/Rockwell backplanes that used those pins for 3.3V injection.

Although, it's only 8 pins total and I suppose I could add a jumper block to reemable PCI3 and PCI4 if someone wanted to use this PISA to PC/104+ adaptor card on "real" PISA/PCISA backplanes with 4 PCI slots...

Yeah, edited.

Would diodes work? Or some switching logic like a Not-and gate that cuts those lines when voltage is present?

Ie reference 3 +3 =0
R3 + 0 = 1

mbandalauk wrote on 2025-08-03, 23:25:

Tevian wrote on 2025-08-03, 11:48:

Okay... I'm looking into it. It shouldn't be too complicated to make an adaptor card for PC/104+. The only issue, I don't have a […]
Show full quote

mbandalauk wrote on 2025-07-30, 04:16:

Yes, PC/104 to ISA adapters are quite common, and as Tevian mentioned above, my PCM-3370 will work fine with one of those when u […]
Show full quote

Yes, PC/104 to ISA adapters are quite common, and as Tevian mentioned above, my PCM-3370 will work fine with one of those when used with his backplane.

However, I'm specifically looking for a PC/104+ (note the plus) to PCISA adapter with an EISA edge connector—see the specification of PC/104+ here:
https://pc104.org/hardware-specifications/pc104-plus/

Adapters with EISA connectors for PC/104+ boards, which include both ISA and PCI, are virtually impossible to find as far as I know. That’s why we believe it might be worth designing one. PC/104+ boards are still relatively common, and many of them are quite capable—making them especially attractive for retro gaming and embedded projects.

Okay... I'm looking into it. It shouldn't be too complicated to make an adaptor card for PC/104+. The only issue, I don't have any PC/104 cards on hand. The technical drawings in the spec sheet look good, so it "should" work. Although, for testing, I'd probably have to get one. 😅

The attachment Screenshot 2025-08-03 042145.png is no longer available

There is an issue of orientation. In the standard versions, with the ISA connector along the bottom edge, all the pins are crossed.

The attachment Screenshot 2025-08-03 043610.png is no longer available

A rotation of 90 degrees clockwise makes the connections a bit more straightforward. This makes the CF card slot point up and should be fine

The attachment Screenshot 2025-08-03 043754.png is no longer available

The next issue is the baffle. A custom PC CARD baffle might not be worth it, so I'm looking for an off-the-shelf one from AliExpress, but I'm not finding one that has all the ports I'd like. A 3D printed one would technically work, but a metal bracket off-the-shelf would be preferred.

The attachment Screenshot 2025-08-03 044450.png is no longer available

The attachment Screenshot 2025-08-03 044513.png is no longer available

Another fantastic contribution to the community! You're right—you’ll likely need a PC/104+ board for proper testing. The 90-degree rotated version looks excellent. I believe my PCM-3370 would fit nicely, and conveniently, the CF slot would face upwards. However, there might be limited clearance between the heatsink and the EISA connector—see the PCM-3370 board below for reference.

I'd be happy to send you mine for testing if that helps. I’m sure we could work something out, though I’m based in the UK, and unfortunately, shipping costs and potential import duties do make things a bit tricky.

I could still do a "standard" orientation but routing might get tricky. The ISA block would be fine with a 2-layer PCB, but adding the PCI would probably need a 4-layer PCB minimum...

As far as clearance, I'd probably have to get an Advantech PCM PC/104 SBC. And, if I use the PCM-3370 as a base, I'd need to verify the dimensions and pin pitch on some of those connectors.

From the pic you posted, although it's not an isometric image, it "appears" to clear the bottom edge from the heatsink while just sticking out over the top. Right now, there's about 24mm from the bottom mounting hole to the edge of the connector pins.

Thank you, BTW, for the offer of sending me your SBC! The shipping and responsibility to send it back might not be worth it. While the shipping of the backplane to you was about $35, I didn't take into account the tax, which pushed that over $50. Don't worry, I'll eat that cost, as I'm still new to shipping internationally. 😅😎

I've purchased a cheap PCM-3353 from eBay that's probably cheaper than the two-way shipping for your SBC. While it has a different set of external connections, it is a PC/104+ card that I could verify works on the adaptor card.

myne wrote on Yesterday, 06:59:

Yeah, edited. […]
Show full quote

Yeah, edited.

Would diodes work? Or some switching logic like a Not-and gate that cuts those lines when voltage is present?

Ie reference 3 +3 =0
R3 + 0 = 1

Here's the issue. The spreadsheet is from the PISA spec sheet, and the red 3.3V is where it differs from the Allen Bradley/Rockwell standard. Including that pecky ground! It would most likely be a jumper block to protect the backplane, even though it has a fuse.

Seems like the GND could be used to switch something.

It's pretty clearly 0 or 3.3.
An and gate?
GND & 3.3reference = connect all the others.
3.3 & 3.3 = cut the others.

myne wrote on Yesterday, 07:20:

Seems like the GND could be used to switch something. […]
Show full quote

Seems like the GND could be used to switch something.

It's pretty clearly 0 or 3.3.
An and gate?
GND & 3.3reference = connect all the others.
3.3 & 3.3 = cut the others.

Oh, wait!!! This is on the card side! I don't need to make provisions for this because I already have on my backplane. All I need to do is follow the PISA spec for this card and everthing should work on a real PISA backplane just like my PCISA-C400. So, non-issue! 😅 It just won't work on the Allen Bradley ones...

Duh!! So I'm shooting for compatibility for those Allen Bradley/Rockwell backplanes then... A jumper block is probably the best cheapest option.