ISA splitter \ VOGONS

ISA splitter

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First post, by Jonas-fr

Posted on 2017-01-26, 10:19

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Hello there,

I'm currently repairing a very nice 486 computer housed in a keyboard (!). It's really cool and I'd like it to become my main 486 battlestation. The only thing it lacks due to space constraints is expansion. It got only one ISA port where I'll hook a soundcard. I was wondering if it was possible to make a passive ISA splitter + extension in order to add a second ISA port? It'll need to be 15-20cm long and flexible in order to let me put the second ISA card somewhere else under the keyboard. I know ISA bus is timing sensitive but I guess that a thin enough flexboard should make it pssible right?

TL;DR Does an ISA expansion+1 to 2 splitter passive adapter exist? Like this PCI-e expansion cord but with an added splitter

Reply 1 of 6, by Jo22

Posted on 2017-01-26, 15:16

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Cool idea, perhaps these threads will fit/help. 😀

Crazy idea: double ISA card.
ISA bus extender using ribbon cable and passive backplane; max length of cable?
Short on ISA slots? Try this.

"Time, it seems, doesn't flow. For some it's fast, for some it's slow.
In what to one race is no time at all, another race can rise and fall..." - The Minstrel

//My video channel//

Reply 2 of 6, by Ampera

Posted on 2017-01-26, 17:25

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Due to the nature of ISA, I would doubt it. It probably would break a lot of cards, and be useless for anything like a video card due to the split bandwidth.

You could technically get two 8 bit ISA slots out of one, but I still don't know if that's possible.

PCI-E is Lane based. A 16x connection can be split into two 8x, four 4x, eight 8x, or sixteen 1x.

Reply 3 of 6, by PARUS

Posted on 2017-01-26, 19:27

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It's possible. It's very possible! But not like PCI-E.
I can say only one: don't use soft cables, use please standard ISA risers and you will not get issues. Forget about limits for video cards etc. You can use any ISA card with riser. Limitation may be only by available resources IO, IRQ, DMA.

Reply 4 of 6, by Jonas-fr

Posted on 2017-01-27, 10:12

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Thanks for your answers. I will have to use softcable/flexcable since the interior of my computer is very cramped (it is actually, entirely housed under the keyboard like an Amiga 1200). In order to avoid IRQ issues etc... do I have to ressort to some extra components/chipset and/or modify the ones which are already present in order to let them know that another ISA port is here?

Reply 5 of 6, by FlashCade

Posted on 2019-10-13, 15:27

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Have you made any progress or collected any more information to achieve the isa splitter? I think it's a very interesting thing for those who want to expand their old pc. Card: ram/ems/hdd/vga/sound...

Ciao

IBM Ps-2 model 30 (8086 / Nec v30) - Tridend 8900d 1024 ram - floppy 720 kb - HDD 20 Mb (KO) - XT CF-Lite v4.1 with 1GB CF Microdrive IBM

Reply 6 of 6, by maxtherabbit

Posted on 2019-10-13, 15:37

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A six slot 5150???

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