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16 bit IO card in 8 bit slot....

P

prime

Experienced Member
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Sep 20, 2009
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Coventry, UK
Hi all,

We know that some some multi IO cards the type that typicaly had IDE/Floppy/Serial/Parallel ports on will work as HD floppy controllers in an 8 bit slot with a driver loaded, as the floppy bit is often 8 bit. Would the same also be true of the serial and parallel ports ?

This would be useful as I only have one 6 pack (which is in my genuine 5150), once I complete building my retro-pc kit.

Cheers.

Phill.
 
I would assume so. UARTs used for the serial port are at least 8-bit chips, and the parallel port interface should also be 8-bit. You can give it a try and see.
 
Worth a try, I have a 16-bit multi i/o card in my 5160, serial and parallel ports working
 
I can confirm the answer is yes, I've done it in the past on my 5160's while waiting for original parts.

You also have the added advantage of being able to do serial transfers at 115,200 baud thanks to the faster UART installed on those cards.
IDE is the only function on them that can't be used generally.
 
SpidersWeb said:
IDE is the only function on them that can't be used generally
Click to expand...

Except with CompactFlash cards and an appropriate BIOS, that is. Some cards will prevent an XT from POST'ing though; not looked in to it in detail still.
 
Yes, usually all 8-bit peripherals (FDC, UARTs, Joystick port, Printer port) on a 16-bit Multi I/O card work on an XT.

I did notice with one XT-clone board that it gives a floppy disk controller error with such (Prime 2C based Multi I/O) card, but this error goes away after a reset.

A word of warning: 16-bit card might interfere with ICs sitting next to the 8-bit ISA slot, and the card might not go all the way into the slot, causing random malfunctions...
 
Would there ever be a situation where using a 16 bit card in an 8 bit slot causes damage, or is the worst case scenario that it simply wouldn't work?

I'm having a devil of a time trying to find an 8 bit RS232 card for my 5160... used to see them everywhere!
 
You're safe to try - all the signals on the 8-bit part of 16-bit cards are of the same designation, except B8 which is n/c in an XT anyway.
 
It wont cause damage.

The dime-a-dozen multi IO cards are very simple - parallel/serial/floppy/game all wired to the 8 bit section - it's only IDE that hooks in to the little extension.

I had someone in NZ asking for a serial card as well, so two days ago I found a random multi io card in my collection, disabled FDD and IDE, popped it in and went through the tests - 115,200 baud with no errors on a 5160 :) There are many other 16 bit cards that can be used in 8 bit slots too.
 
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