PDA

View Full Version : IBM Asynchronous Communications Adapter



marcoguy
May 4th, 2012, 02:06 PM
I have heard from multiple sources that the ISA slot in the IBM 5160 nearest the 8088 CPU is reserved for the IBM Asynchronous Communications Adapter, which this source : http://www.minuszerodegrees.net/5150_5160/cards/5150_5160_cards.htm says is pretty much a serial card. Can I stick any old serial card in that slot, or does it have to be IBM?

Great Hierophant
May 4th, 2012, 03:05 PM
I have heard from multiple sources that the ISA slot in the IBM 5160 nearest the 8088 CPU is reserved for the IBM Asynchronous Communications Adapter, which this source : http://www.minuszerodegrees.net/5150_5160/cards/5150_5160_cards.htm says is pretty much a serial card. Can I stick any old serial card in that slot, or does it have to be IBM?

You can stick a serial card that has specific support for XT slot 8. IBM's was probably not the only one to do so. I believe you can also insert the extender card for the IBM PC Expansion Unit.

marcoguy
May 4th, 2012, 03:27 PM
You can stick a serial card that has specific support for XT slot 8. IBM's was probably not the only one to do so.
Do you know the name of one or where I can get one?


I believe you can also insert the extender card for the IBM PC Expansion Unit.
Yeah, I totally wish I had an expansion unit. I could do so much....

Chuck(G)
May 4th, 2012, 03:41 PM
Any board with a 0WS jumper will work just fine in slot 8. The pin was (sort of) repurposed on the PC/AT to indicate that an extra wait state should not be inserted with bus accesses.

On slots 1-7 on a 5160, this pin ( B08 ) doesn't go anywhere. On slot 8, this serves to disable other cards from driving the data bus and the lower 8 bits of the address bus.

The slot isn't reserved explicitly for the async card. Any card that can assert B08 when selected will work fine.

marcoguy
May 4th, 2012, 03:48 PM
I guess I'm a little more software oriented than hardware when it comes to vintage computing. How would I know if my card supports B08?

Chuck(G)
May 4th, 2012, 04:40 PM
The easiest way that I know of is to look at the edge connector pin B08. Does it go anywhere or is it missing or just a go-nowhere contact? If either, then the card doesn't support B08.

marcoguy
May 4th, 2012, 04:47 PM
Okay, so I went through all of my cards, and the one I hoped to put in the 8th slot didn't have a connecter at B08, but my SCSI controller does. I'll put that there.

marcoguy
May 22nd, 2012, 05:16 PM
So... What exactly does the Asynch do? I guess I should have asked this first!

SpidersWeb
May 22nd, 2012, 05:20 PM
The async card is just a serial port. My 5150 has one, 5160 had the later 9 pin + parallel card.
Just ordered a 25pin to 9pin serial adaptor yesterday (cost me all of 5 bucks new).

marcoguy
May 22nd, 2012, 05:29 PM
Oh, okay. Thanks.

Stone
May 22nd, 2012, 05:41 PM
Just ordered a 25pin to 9pin serial adaptor yesterday (cost me all of 5 bucks new).Ya' shoulda' told me. I woulda' thrown one in that box of stuff I sent ya'.

pearce_jj
May 22nd, 2012, 09:55 PM
Any board with a 0WS jumper will work just fine in slot 8. The pin was (sort of) repurposed on the PC/AT to indicate that an extra wait state should not be inserted with bus accesses.

On slots 1-7 on a 5160, this pin ( B08 ) doesn't go anywhere. On slot 8, this serves to disable other cards from driving the data bus and the lower 8 bits of the address bus.

The slot isn't reserved explicitly for the async card. Any card that can assert B08 when selected will work fine.

When experimenting with this I found that it must only be asserted for reads, i.e. pretty much a reflection of /IOR or /MEMR.

SpidersWeb
May 23rd, 2012, 02:35 AM
Ya' shoulda' told me. I woulda' thrown one in that box of stuff I sent ya'.
haha cheers, to be honest I didn't know I'd need it until about two days ago when I looked behind the 5150 and remembered it didn't have 9 pin.

per
May 23rd, 2012, 03:05 AM
When experimenting with this I found that it must only be asserted for reads, i.e. pretty much a reflection of /IOR or /MEMR.
Unlike the PC, the XT actually has two inrernal busses; a bus from the CPU to the 7 "regular" ISA slots, and another bus for the system board components and ISA slot 8. The two busses are connected together with buffers and bus-transceivers.

The /CARDSELECT signal in ISA slot 8 will just choose what direction the bus-transceiver will forward data. When low, data will go from the internal system bus to the CPU bus, which is why it is needed for reads only.

pearce_jj
May 23rd, 2012, 03:35 AM
per, do you know what is meant in the service manual by the reference to timing requirements being more strict in slot 8?

per
May 23rd, 2012, 04:22 AM
per, do you know what is meant in the service manual by the reference to timing requirements being more strict in slot 8?

That's just the delay in the transceiver. When a regular ISA cards is read from, it detects /MEMR or /IOR and immediately outputs data. A card in slot 8 has to detect /MEMR or /IOR, activate the /CARDSELECT signal, output data and then wait for the transceiver to forward it to the CPU bus. This may in the worst cases take up something like 100ns more than with regular ISA cards (depending on the implementation).

In other words, cards in ISA Slot 8 just has to respond a little faster when read from compared to the other ISA Slots. I don't think it should be too much a problem for most cards, and remember that IBM used to play it very safe regarding keeping things within specifications.

pearce_jj
May 23rd, 2012, 04:34 AM
Thanks very much - hopefully not something I need to worry about with my CPLD code then.

bettablue
May 25th, 2012, 07:28 PM
According to what I read during my initial assembly, the extender and receiver cards for the expansion unit had to be the furthese away from the power supply. That is what I did in mine, and the expansion works fine. Now I'm not sure how that relates to the CPU, because I also have an AST six pack plus with an asynchronous communications port. The AST card is working fine in slot 3, with slot 1 and slot 2 taken up by the floppy controler and my CGA video adapter. The funny thing here too is that my CGA adapter doesn't have a composite out, but instead, it has another parallel port which on my computer is LPT2. So far I haven't had any issues with things not working. In fact, everything that's been installed into my 5150 seems to be working as intended; including the expansion unit. I don't know if that is any different between the 5150 and the 5160 though.

Hope this helps.


You can stick a serial card that has specific support for XT slot 8. IBM's was probably not the only one to do so. I believe you can also insert the extender card for the IBM PC Expansion Unit.

Chuck(G)
May 25th, 2012, 09:18 PM
There is a difference. The 5160 has the "special" Slot 8, the 5150 does not.

But then, the 5150 has only 5 expansion slots.

http://img845.imageshack.us/img845/937/homerdoh.png

bettablue
May 26th, 2012, 10:15 AM
Thanks chuck. I resemble that. But now that it's been brought up. Are there any slot restrictions in the 5150 that I should be aware of? Aside from the expansion unit I mean. Or for that matter, does it really matter which slot the extender card is installed to?



There is a difference. The 5160 has the "special" Slot 8, the 5150 does not.

But then, the 5150 has only 5 expansion slots.

http://img845.imageshack.us/img845/937/homerdoh.png

Chuck(G)
May 26th, 2012, 10:30 AM
According to the schematic(s) of the 5150, all slots are created equal--although it's just good practice to place faster devices closer to the CPU (i.e., closer to the power supply).