I see those regularly, and wondered what would happen if for example, I put an ISA 486 computerboard into a 386 motherboard, removing the ram and cpu and bios from the 386 motherboard ?
IF you remove all that from the motherboard, I imagine it won't boot, since without the CPU/RAM/BIOS, it'll have no way to bootstrap itself.
And the ISA bus maxes out at 8 Mbytes/sec transfer speed, so that 486 board would basically be crippled by the bus itself, to begin with.
The daughterboards I've seen for Amigas and older Apples (Orange 486/ 040 boards) were like coprocessors, but they still relied on the host PC to be able to load it.
I once had a few socket 370 SBCs that maplins were selling as upgrades to ISA systems. They more or less just used the old motherboard as a physical mount however. In fact they might even still be available:
http://www.azak.ie/hypertec1.htm
I don't know if they were similar to industrial SBCs that communicate to peripheral boards through a backplane though, which is I think what you are referring to. You are asking whether an old motherboard minus key components could serve as a passive backplane for a single board computer? Like this:
http://www.ebay.co.uk/itm/MICROBUS-BACK-PLANE … 3-/400267115742
Interesting question, would love to know too.
wrote:I once had a few socket 370 SBCs that maplins were selling as upgrades to ISA systems. They more or less just used the old motherboard as a physical mount however. In fact they might even still be available:
http://www.azak.ie/hypertec1.htm
I don't know if they were similar to industrial SBCs that communicate to peripheral boards through a backplane though, which is I think what you are referring to. You are asking whether an old motherboard minus key components could serve as a passive backplane for a single board computer?
I think your are correct about it being industrial. Older 386s/486s tended to use a "co-processor" socket, which basically disabled the original CPU. The only daughterboards I know of that worked in concert with the original mobo were Macs and Amigas, so talk all this with a grain of salt.
wrote:I see those regularly, and wondered what would happen if for example, I put an ISA 486 computerboard into a 386 motherboard, removing the ram and cpu and bios from the 386 motherboard ?
Unfortunately, this may not work if the subject is an industrial SBC. An industrial SBC and a normal motherboard are both active boards (host type) even without CPU and BIOS installed. Putting them together will cause many signal conflicts such as clock, reset ... etc. However, a normal motherboard can be converted into passive backplate. During my test with a broken 486 motherboard, I step by step removed CPU, BIOS, OSC Crystal, Chipset ... until most of the gate ICs, the SBC finally worked when plugged into an ISA slot on the "passive" motherboard. It could be powered by the standard PSU via the ISA slot, and it can drive other cards in other ISA slots on the same motherboard (such as sound card). Apparently, the modification to the normal motherboard is destructive and irreversible.
wrote:wrote:I see those regularly, and wondered what would happen if for example, I put an ISA 486 computerboard into a 386 motherboard, removing the ram and cpu and bios from the 386 motherboard ?
Unfortunately, this may not work if the subject is an industrial SBC. An industrial SBC and a normal motherboard are both active boards (host type) even without CPU and BIOS installed. Putting them together will cause many signal conflicts such as clock, reset ... etc. However, a normal motherboard can be converted into passive backplate. During my test with a broken 486 motherboard, I step by step removed CPU, BIOS, OSC Crystal, Chipset ... until most of the gate ICs, the SBC finally worked when plugged into an ISA slot on the "passive" motherboard. It could be powered by the standard PSU via the ISA slot, and it can drive other cards in other ISA slots on the same motherboard (such as sound card). Apparently, the modification to the normal motherboard is destructive and irreversible.
That's... rather fascinating. Would have loved to have seen that in action. Make a video next time. 😀
"I see a little silhouette-o of a man, Scaramouche, Scaramouche, will you
do the Fandango!" - Queen
Stiletto
wrote:That's... rather fascinating. Would have loved to have seen that in action. Make a video next time. 😀
Forgot to take a video, but found two photos:
wrote:I think your are correct about it being industrial. Older 386s/486s tended to use a "co-processor" socket, which basically disabled the original CPU. The only daughterboards I know of that worked in concert with the original mobo were Macs and Amigas, so talk all this with a grain of salt.
They existed for Microchannel machines as well. MCA allowed bus mastering to the level that CPU upgrade cards could be used. It was also cost effective (relatively speaking) to upgrade PS/2s since the machines were so expensive new.
wrote:Forgot to take a video, but found two photos: […]
wrote:That's... rather fascinating. Would have loved to have seen that in action. Make a video next time. 😀
Forgot to take a video, but found two photos:
Thanks! That's very neat!
"I see a little silhouette-o of a man, Scaramouche, Scaramouche, will you
do the Fandango!" - Queen
Stiletto
wrote:Forgot to take a video, but found two photos: […]
wrote:That's... rather fascinating. Would have loved to have seen that in action. Make a video next time. 😀
Forgot to take a video, but found two photos:
You broke a great ASUS VLB mobo to make a passive board? Your heart must be made of stone! Was there no junk available, like some PCchips with fake cache soldered on or Lucky Star with smelly VRMs? Please tell me the board was not functional...
wrote:They existed for Microchannel machines as well. MCA allowed bus mastering to the level that CPU upgrade cards could be used. It was also cost effective (relatively speaking) to upgrade PS/2s since the machines were so expensive new.
Huh! Learn something new everyday! 😁
The only PS/2 I got to use was in math class in highschool, and taking it apart was verboten. (Although the Computer Teacher and I were champing at the bit to do so).
wrote:You broke a great ASUS VLB mobo to make a passive board? Your heart must be made of stone! Was there no junk available, like some PCchips with fake cache soldered on or Lucky Star with smelly VRMs? Please tell me the board was not functional...
Lol, I'm more than glad to read this and my heart is no different from other hearts here 😀 -- yes, that was a deeply damaged mobo (as I mention in my first reply to this thread) I will normally do everything to rescue a mobo if possible, or otherwise try to make good use of the zombie but barely abandon it to recycling.
wrote:wrote:You broke a great ASUS VLB mobo to make a passive board? Your heart must be made of stone! Was there no junk available, like some PCchips with fake cache soldered on or Lucky Star with smelly VRMs? Please tell me the board was not functional...
Lol, I'm more than glad to read this and my heart is no different from other hearts here 😀 -- yes, that was a deeply damaged mobo (as I mention in my first reply to this thread) I will normally do everything to rescue a mobo if possible, or otherwise try to make good use of the zombie but barely abandon it to recycling.
Thou art forgiven 🤣
What if you disable the conflicting signals, and just leave GNG and VCC ? I mean this single board PC should only need them and nothing else? I am wondering if I could just "block" contacts on ISA card by for example capton tape?
https://en.wikipedia.org/wiki/Industry_Standa … XT_Bus_pins.svg
If you block all the signals except for power and ground it will operate independently from the motherboard/backplane. But why bother? All the cards you add to the system would be controlled by the base motherboard. You may as well take the board out an power it separately.
What would be interesting would be to have a board work with the motherboard. Some backplanes have multiple ISA buses, I guess so you can fit multiple PCs in one case. For example 4 slots for one bus 4 for another. Guess you could have a simple I/O card that connects the two together that has a register/RAM/I/O port to allow communication between them. A loosely-coupled dual CPU system of sorts. There was at least one early upgrade board for PC/XTs that you could switch to-from with software. I only read about it in infoworld or PCmag.
