• Please review our updated Terms and Rules here

IBM PC 5150 model A in europe?

I agree with Per. Check the motherboard switches first. 4 failing bits in the one bank is highly unlikely. You have a 64/256K board (implying third BIOS revision). Therefore, with the only RAM being the 4 banks on the motherboard, the switches should be:
Switch Block 1: Switches 3 and 4 both off (enable all 4 motherboard banks)
Switch Block 2: Switch 1 on, 2 off, 3 off, 4 on, 5 on (256KB total RAM)

Switch Block 2 is the one at the edge of the board.
Note that we've seen some people confuse off with on.
Switches 6/7/8 on Switch Block 2 can be set to either off or on - they aren't wired to anything.
 
There is something strange here, the dip switches are ALL turned on: the eight switches in switch block 1 and also 1/2/3/4/5 from switch block 2. I set them in this way because I removed all RAM ICs from banks 1,2 & 3, removed the floppy controller and put a VGA card.

If the error points to a failure in Bank 1... why is the bios testing this bank if it is turned off? I will measure continuity in dip switches, maybe they are not working.

Chuck, at the moment I only have VGA monitors. And the previous owner told me that the MDA card on this PC is not working. He didn't know that power supply was shorted, motherboard had bad tantalums and one had exploded, the ram issues...
 
These 5150 motherboards can do weird things. For example, with a 16/64K motherboard that has it's original BIOS (which will be either first or second revision), one can switch off/on the four banks as required. Upgrade the BIOS on that board to the third revision, and you'll discover that all 4 banks of RAM must be populated (in contradiction with IBM's own documention for the upgrade).

That third BIOS (found on all 64/256K motherboards) does something similar with my 64/256K board, with the difference being that a minimum of 3 banks need to be populated. So reinstall all 4 banks of motherboard RAM, set the switches appropriately, then see how you go.
 
You were right again, with only one or two banks the error appeared no matter how were the dip switches. With the four banks fully populated the board seems to be ok. Now I need a compatible keyboard, my model M from a PS/2 Mod. 30-286 don't work here with a MiniDIN to DIN adapter...
Thank you very much!
 
nestor said:
You were right again, with only one or two banks the error appeared no matter how were the dip switches. With the four banks fully populated the board seems to be ok. Now I need a compatible keyboard, my model M from a PS/2 Mod. 30-286 don't work here with a MiniDIN to DIN adapter...
Thank you very much!
Click to expand...

Wasn't there an AT-to-XT(-and-PC) keyboard adapter made some time ago? This device is very usefull if you don't have access to an actual PC or XT keyboard. I don't know if forum member Hargle got any kits them left, but you may try to PM him just in case.
 
You mean the AT2XTKBD project? I will check if I can adapt the source code to work on a PIC 16F88 (I have some around). It will be faster than wait for the kit to arrive...
I enjoy this kind of projects, like the XT-IDE!
 
You must log in or register to reply here.
Back
Top