AT&T PC6300/Olivetti M24 P8 Video Card jumpers?

[Chuck(G)]

Oh, this 6300 box is maddening. At any rate, it looks as if the original owner disabled the onboard video card; now I'm trying to figure out how to re-enable it.

I've got the P8 revision video adapter.

Motherboard SW1, 5 and 6 are set off (monochrome).

The jumper block up at the top of the board next to the crystal oscillator is set to 2-3 and 5-6.

Jumper W1 is set to 2-3
Jumper W2 is set to 1-2
Jumper W3 is set to 1-2

And there's a wired header block at 5H.

The upshot is that the board remains disabled; the video RAM isn't even mapped in.

Can anyone compare what they have with this and tell me how theirs is set up. I can't seem to find a schematic for the P8 board (only the P2) which is hindering me somewhat.

 

[ahm]

For the P8 VDC, I only have a cheat sheet and not everything is labelled.

W1: 2-3 enable

Jumper A: 2-3, 5-6 enable

The block "south" of W1 should always be 1-2

The block which is roughly south-east of center should always be 1-2

As for the motherboard, SW 1 (7W), you may want to try switches 5 and 6 as 1 0.

What's your ROM version?

 

[Chuck(G)]

My BIOS is 1.43--and this system has been upgraded. There's a piggyback board replacing the keyboard controller with a TI 7000 uC, EPROM and some TTL glue. There's also a small board plugged into the "high order" connector of the expansion slot that has a bipolar PROM (82S147) on it and has a ribbon cable that goes to an IC on the bus converter (backplane) board.

As mentioned, I've set the jumpers (the way you mention) in accordance with the illustration on page A-34 of the service manual. But it's the 20 pin jumper plug at 5H that I'm wondering about. What's supposed to be there on a normal card? I've tried all 4 combinations of 5 and 6 on SW1; no difference.

 

[ahm]

I only have this cheat sheet, so I have no idea where 5H might be.

But there is a cryptic note: "To disable the P4 VDC, check to see if 74LS00 is socketed or soldered because it does not have the Jumper Block to disable it. If the chip is soldered then get the vdeo bridge adapter to disable. Otherwise, it it's sockered, get the reconfiguration chip. THIS IS ONLY FOR THE P4 VDC." and a diagram for a 14-pin "disabler chip".

 

[Chuck(G)]

Yes, the service manual has the description of the P4 plug, but this is the P8 which has a 20-pin shunt plug installed (the LS00 is only 14). My guess is that something like an LS244 or LS374 might have been installed there, but I have no way to verify that. I guess I could trace out the lines on the PCB and try to put some ideas together, but I'd rather find someone with a P8 display board and know for certain.

You know the feeling, I'm sure.