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Need ISA Compatibility

By GuruOfDos ·
Many new motherboards do not have ISA slots and here is my dilemma. I build 'industrial control' systems and simulators, and most of the communication to the outside world is via 24 digital I/O lines from an 8255 IC on a custom built ISA card. Believe it or not, no matter how much processor speed you want to perform the maths, an 8 Mhz bus is more than sufficient for operating relays, logic circuits etc. Our cards also contains some other electronics (wasn't full length ISA prototyping wonderful!!), but this is not an issue here - so long as I can get a 16 bit ISA bus or 24 (4 lines of Digital I/O..the external interfacing can be located anywhere! I'm looking for something that will EITHER give me effectively an ISA bus ( perhaps a PCI to ISA bridge on a PCI card, with a ribbon cable to an external 'bus box', with several ISA slots) OR an alternative to a 24 line DIO card in PCI format that I can access via DOS or C's INP/OUT commands to directly read and write bits/bytes to and from the 3 8 bit ports. I don't want to go to an industrial case and specialist (expensive) motherboard... I want to keep it in desktop PC (AT/ATX) form if possible. Any suggestions folks?

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Need ISA Compatibility

by tlippert In reply to Need ISA Compatibility

Built four machines for a shop just like yours two months ago. Specs were 5 PCI, 2 ISA. Finding the boards was like searching for the holy grail. Found them at

http://www.addonshop.com/cgi-bin/showitems.cfm?ItemID=79&CategoryID=1

Hope this helps.

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Need ISA Compatibility

by GuruOfDos In reply to Need ISA Compatibility

Gigabyte do a board. GA-7IEX4 or somesuch, but I'm looking at onward sourcing....most boards out now are only going to be available for a little while longer, but not forever! And I need >1GHz Athlon....NOT Intel. Thanks anyway :-)

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Need ISA Compatibility

by csmith In reply to Need ISA Compatibility

One of the boards we use is the EPOX 8KTA3.
It has an ISA slot, and is a good motherboard.
My main question is, why not adapt the ISA design to PCI?
Except for the PCI latency problem, this should not be so hard to do. (They have managed to change Printer and COM cards. Also very slow cards.)
A side question: Why are you not using assembler In and Out commands?
You can access it from C, and they are not that complicated, that excessive programming time is consumed.
Does this board use polling, instead of an interrupt?
Why do you have to have ISA?
Is the 8255 so slow, that you can't safely buffer it?
Of course the last question is, who/where is the engineer that originally designed this board?
These questions are also ideas.
Regards, Chris

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Need ISA Compatibility

by GuruOfDos In reply to Need ISA Compatibility

I designed the board myself, about 8 years ago. Converting to PCI will be prohibitively expensive and out of the question for the volumes we require them in (3 or 4 per year - we make VERY specialist systems!) and we still have a good stock of ISA cards. Our programming is done in Visual Basic (with a dll call for I/O). The board uses polling as it is only writing ones and zeros to output lines controlling relays etc, and reading status of sensors and switches. We did toy with using a CPLD (Coolrunner) to emulate a PCI Interface, but the plug and play and actual interfacing was beyond us and we were quoted in the thousands (GBP) to have it done for us :-(. We also use 3 isa slots, so one on a board doesn't help. Thanks anyway!

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Need ISA Compatibility

by csmith In reply to Need ISA Compatibility

3 or 4 per year? Ouch! No R&amp budget on that.
The problem of the single slot, is not really a problem, because you can use old Packard Bell ISA Extender Cards. (Remember the old Packard Bells had only one ISA Slot with a Riser Card plugged into it.)
The assembly code was 9**09-**3-623, and the PCB code was 93004-**6-410.
These things look like the old 30 pin SIMM extenders that were sold for 386 and 486s, only for ISA.
The card is standard height, but the daughter cards will be at a right angle to the standard positition.
Are you set up to modify a standard case?

How much processor (CPU) power do you need?
Another option is to buy a bunch of used MBs.

Regards, Chris

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Need ISA Compatibility

by GuruOfDos In reply to Need ISA Compatibility

1GHz is ample...thats for the video capture and replay side of things. Tha actual I/O and hardware control will run on a 486 DX33!

I have countless extender boards (PB, IBM, Elonex) and can manufacture them if necessary, so I guess that is probably the best option as regards extending slots. My preferred alternative (on similar lines) is to make a simple proto ISA card with the 30 or so relevant lines (Address, Data, IORW etc) buffered with some standard 74 series TTL Buffers brought out on an IDC cable. Fit the ISA cards on a 4 Slot passive ISA backplane in a separate case and have a matching Proto card to take the IDC cable and convert back to ISA pin-out. Used or second-hand mobo's are out as the systems are for military and police use so have to be subject to pretty stringent QA checks. Thanks for the advice though...my gut feelings were drifting that way so that's my probable way forward.

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Need ISA Compatibility

by csmith In reply to Need ISA Compatibility

Cancel the idea about using a Packard Bell riser card.
The daughter cards would point off of the end of the Motherboard. (Down in a tower case.)
Another idea would be to increase the efficiency of the program, instead of using a more powerful CPU.(You would be burned at the stake, for expressing this idea, at Microsoft.) The question is of course the available time, and the economics of it.
Regards, Chris

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Need ISA Compatibility

by GuruOfDos In reply to Need ISA Compatibility

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