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SomeGuy
August 4th, 2013, 03:30 PM
Probably a dumb question, but what is this unused spot next to the keyboard plug for? (marked "PC" on the picture below) I've noticed a number of XT clone boards have this empty spot for a plug. It wouldn't happen to be for a cassette port would it? I don't recall any of IBM's XT machines having a cassette port.

14658

GottaLottaStuff
August 4th, 2013, 04:24 PM
Cassette port on the 5150 is in that spot.

krebizfan
August 4th, 2013, 04:27 PM
With a picture of the underside of the motherboard, it would be easier to tell. Find the chip the connector feeds and that would tell the function. Early boards did seem to be intended to have a cassette port despite a lack of clone BIOSes that supported cassette operation. Later boards were designed with some type of mouse port in mind.

SpidersWeb
August 4th, 2013, 04:36 PM
Is that a DTK PIM-640 by chance?

As above, it's where the original PC had it's cassette connector, so a likely reason.

Chuck(G)
August 4th, 2013, 05:27 PM
I don't think so--the whole group is labeled P5 and the pad spacing doesn't make sense. My suspicion is that instead of a DIN-5 connector, a different one can be fitted. Check the non-ground pads--I suspect there's continuity with the regular DIN-5 pads.

At least that's my guess--I've got a couple of clone boards like that and never got curious enough. A photo of the bottom of the board might shed some light.

Relative to the XT mounting, does a 5150 have a keyboard connector in exactly the same place? I've seen XT clone boards where pads for 5 ISA slots can be fitted. How about this one? The idea was that there was a market for upgrading old 5150s by swapping the motherboard.

k2x4b524[
August 4th, 2013, 08:18 PM
so on some clone boards, if you had the balls to move slots around and do it right, you could put a clone board in a 5150, just by moving the slots around? Fascinating, but i do agree, some of those boards have pads where one would put the cassette connector, or say, a proprietary keyboard, but the side by side keyboard mouse plugs didn't show up until the 386 era did they?

SpidersWeb
August 4th, 2013, 08:39 PM
On PCs you didn't really see keyboard+mouse together until the PS/2 came out AFAIK. My oldest are a Model 30 286 and an NEC PowerMate 286.

I'm thinking Chuck is on to something there, but I can't check it for myself until I get home. I just restored a DTK PIM-640 which has the identical top corner. In the middle of my board is solder points for one more ISA slot, squished between the others, and the others don't quite seem to line up nicely with my case supports and I'm wondering if that was on purpose so in it's alternative setup it could be used in 5 slot clone case or similar. Find out when I get home, unless the OP beats me to it :)

Edit: oh and if it is a PIM-640, there is from what I can tell, no settings for mouse or cassette options.

SomeGuy
August 4th, 2013, 10:05 PM
I don't think so--the whole group is labeled P5 and the pad spacing doesn't make sense. My suspicion is that instead of a DIN-5 connector, a different one can be fitted. Check the non-ground pads--I suspect there's continuity with the regular DIN-5 pads.
Ok, I should have seen that earlier, they do show continuity to DIN-5 ones. The middle one is ground and the others, I think, were clock and data.

So it is for some other kind of keyboard connector.... but still, what kind of keyboard and connector would use that?

k2x4b524[
August 4th, 2013, 10:21 PM
Ok, I should have seen that earlier, they do show continuity to DIN-5 ones. The middle one is ground and the others, I think, were clock and data.

So it is for some other kind of keyboard connector.... but still, what kind of keyboard and connector would use that?


I'd say it's probably for the same 5-pin, but maybe for a different kind of case, maybe an industrial layout?

SpidersWeb
August 4th, 2013, 10:43 PM
I just compared my DTK PIM-640 with an IBM 5150 motherboard.

In it's current position, the keyboard connector would not line up in a 5150 case, its a few mm too far to one side. By moving it left half a spot (where those extra joins are), it lines up perfectly with the 5150 keyboard port.
The 8 ISA slots are offset a little wrong - this incorrect offset means in a 5150 case you'd get 2 slots lined up perfectly, and you can add a one in the middle - so that's 3 perfectly matched external cards (and 5 internal only slots).

So yeah, my guess is it's for someone upgrading their 5150.

Flamin Joe
August 4th, 2013, 10:56 PM
On PCs you didn't really see keyboard+mouse together until the PS/2 came out AFAIK. My oldest are a Model 30 286 and an NEC PowerMate 286.

True I don't think it become a standard as such until the PS/2. However there are some examples of the keyboard/mouse being placed together on a motherboard on earlier systems. Atari had a line of IBM PC Compatibles back in the late eighties and I believe the PC3, which was an 8088, was the first model in their series which had the keyboard and mouse port next to each other on the side of the case.

SpidersWeb
August 4th, 2013, 11:07 PM
Motherboard comparison pic (sorry I didn't want to pull the DTK out) http://i83.photobucket.com/albums/j307/DrRabid/Vintage/IMG_0082_zpsa0faf038.jpg and http://i83.photobucket.com/albums/j307/DrRabid/IMG_0080_zps9a502ac5.jpg (yes I know my DTK needs a wash)

Bad pics but hopefully you can see slot 1 and 5 line up 100%, slots 2 and 4 almost line up, and slot 3 lines up perfectly with the solder spots for another ISA connector. The 5150 keyboard connector lines up to the solder spots marked PC.

FJ - haven't laid my eyes on an Atari PC yet, might have to look that up - I'm guessing it came with a GUI? I remember the Commodore PCs (had a PC10 once upon a time) some very creative minds in those companies.

Flamin Joe
August 5th, 2013, 03:11 AM
FJ - haven't laid my eyes on an Atari PC yet, might have to look that up - I'm guessing it came with a GUI? I remember the Commodore PCs (had a PC10 once upon a time) some very creative minds in those companies.

Yes it had it's own GUI. Earlier models (PC1, PC2, PC3) weren't really capable of running Windows so Atari ported the same GEM GUI as found on the Atari ST to the IBM PC. They also came with MS-DOS 3.21.

Without derailing the thread too much, I've got some pics in my gallery of a PC3 which is on it's way to me. There's a close up pic of the keyboard and mouse port together on the side of the case in there as well.

http://www.vintage-computer.com/vcforum/album.php?albumid=208

Very well built and designed, but considered a bastard child by many traditional Atari fanatics. :)

geneb
August 5th, 2013, 08:18 AM
Atari did no such thing. GEM for the PC was done by Digital Research, whivh is also where Atari got GEM to begin with.

g.

Chuck(G)
August 5th, 2013, 08:45 AM
There were many 16-64K 5150s sold and one of these boards, properly populated was an inexpensive upgrade to one. I'm not aware that IBM made the 64-256K 5150 mobos available as upgrades, but even if they did, it would be at a significant premium.

Almost no one used the audio recorder interface anyway.

SomeGuy
August 5th, 2013, 08:58 AM
Motherboard comparison pic (sorry I didn't want to pull the DTK out) http://i83.photobucket.com/albums/j307/DrRabid/Vintage/IMG_0082_zpsa0faf038.jpg and http://i83.photobucket.com/albums/j307/DrRabid/IMG_0080_zps9a502ac5.jpg (yes I know my DTK needs a wash)

Bad pics but hopefully you can see slot 1 and 5 line up 100%, slots 2 and 4 almost line up, and slot 3 lines up perfectly with the solder spots for another ISA connector. The 5150 keyboard connector lines up to the solder spots marked PC.
Ok, that seems to solve the mystery. The IBM PC 5150 keyboard plug is positioned slightly to the left of where it is on an XT, and these XT clone boards could be modified to somewhat fit in an original IBM PC case.

Never had a chance to see the two side by side like that - I always thought the keyboard connectors were positioned the same - thanks for the picture. And the board I was looking at does also have those solder points for the extra slot. (Always thought that was for a riser or expansion system, but there we have it)

Although, after thinking about it, it would be kind of cool if a cassette port could be added to an XT or AT class machine.

vwestlife
August 5th, 2013, 09:22 AM
I just restored a DTK PIM-640 which has the identical top corner. In the middle of my board is solder points for one more ISA slot, squished between the others, and the others don't quite seem to line up nicely with my case supports and I'm wondering if that was on purpose so in it's alternative setup it could be used in 5 slot clone case or similar.

That's probably for a riser card, for LPX-style low-profile cases where the ISA slots are horizontal.

Stone
August 5th, 2013, 10:23 AM
Hey, if you need a riser card, lemme know:

14685 14686

Flamin Joe
August 5th, 2013, 04:53 PM
Atari did no such thing. GEM for the PC was done by Digital Research, whivh is also where Atari got GEM to begin with.

g.

Your correct. Wrong use of the word ported. I meant ported as in they brought it across from the Atari ST line and used with their PC line as well. They didn't actually develop it.

Anyway this is all going off topic and should really be in another thread. :)

SpidersWeb
August 5th, 2013, 05:23 PM
That's probably for a riser card, for LPX-style low-profile cases where the ISA slots are horizontal.

Was that common in 85/86?

vwestlife
August 5th, 2013, 09:24 PM
Was that common in 85/86?

I don't think so, but once IBM introduced the PS/2 Model 30 in 1987, a lot of clone makers followed suit with similar low-profile cases using a riser card for the ISA slots, such as the NEC V20-based CompuAdd 810:

http://img.photobucket.com/albums/v93/zzm113/compuadd/HPIM0696.jpg

Chuck(G)
August 5th, 2013, 10:19 PM
Generally, you only saw riser cards when the planar had added functionality (e.g. floppy, display, parallel/serial ports) where a small number of expansion cards made sense. However, this is a plain-Jane XT-type board.

You could purchase 5150-style boards with 25 mm spacing between I/O slots instead of the 20 mm XT spacing. You could even get, IIRC, 80286 upgrade cards.

But since the real rush of clones didn't come in until the 5160, they're not as common.

But the Big Blue Seed manual shows one of these "hybrid" boards.

SpidersWeb
August 5th, 2013, 10:45 PM
I don't think so, but once IBM introduced the PS/2 Model 30 in 1987, a lot of clone makers followed suit with similar low-profile cases using a riser card for the ISA slots, such as the NEC V20-based CompuAdd 810:

Ah yep this motherboard is from 1986, probably designed in 1985 so by the sounds of it it's probably for 5150 case options rather than a riser.
I was curious because the riser theory would also make sense and then I'd need to go take resistance measurements of the "PC" connector to double check but now I can sleep easy and put the poor thing back together. I bought it to do a restoration video, but the damn thing worked fine.

Chuck(G)
August 6th, 2013, 07:47 AM
Some of these old XT motherboards also have a set of (unpopulated) additional power supply pads. Strange as it seems, these were for use with Apple-type power supplies.

SpidersWeb
August 6th, 2013, 02:02 PM
Yeah the one I used in the photos (DTK PIM-640) has those solder pads for the extra PSU connectors.

Anonymous Coward
August 7th, 2013, 06:38 PM
I'm really interested in the Compuadd 810. Doesn't the BIOS on that system support extra goodies like high density floppy drives and extended keyboards? Would it be possible to get a dump of the BIOS?

vwestlife
August 8th, 2013, 06:59 AM
I'm really interested in the Compuadd 810. Doesn't the BIOS on that system support extra goodies like high density floppy drives and extended keyboards? Would it be possible to get a dump of the BIOS?

Yes... even though CompuAdd only ever shipped it with a 360K drive, the 810 has support for high-density drives on its on-board floppy controller. It also has an on-board Western Digital IDE-XT hard drive controller, although for some reason I can't get mine to work, even with known-good IDE-XT drives.