General Stuff(tm)

[rubber_jonnie]

Yeah, I ordered the QL minerva ROM from eBay Germany and it turned out I was already chatting with the seller on the QL forum!!

Does the Overdrive run at 33Mhz bus speed?

It's been a while since I played with one, and the 486 I have is already a DX2/66, so I can't remember how they did it all.

Yeah, the Intel DX2's are 5V and the 66MHz part basically clock doubles internally.

:lol: I actually remembered it right :)

Is it a ZIF socket, or are you going to have to pry the old CPU out?

[BennehBoy]

A 486 66mhz DX2 was my first PC, it was pretty good for Quake :D

[stephen_usher]

:lol: I actually remembered it right :)

Is it a ZIF socket, or are you going to have to pry the old CPU out?

It's gently pry it out with an electrical screwdriver time.

[rubber_jonnie]

:lol: I actually remembered it right :)

Is it a ZIF socket, or are you going to have to pry the old CPU out?

It's gently pry it out with an electrical screwdriver time.

I never liked those 'gotta pry it out' sockets :cussing:

[stephen_usher]

They were the normal type until at least the Pentium era when you required coolers attached to the socket.

[stephen_usher]

I couldn't get the machine to boot at all with the MRBIOS for some reason, but managed to get it to boot with the original BIOS eventually.

After a bit of toing and froing I managed to get the 486DX2-66 working. I had to straighten a few pins for a start.

I'm soak testing the M/B out of the case at the moment, using CheckIt running full memory tests.

[stephen_usher]

Whatever the fault is it's getting worse. I can hardly ever get it to POST.

'Scoping the pins on the ROM, most of the time there is zero activity. When it doesn't start up the /CE pin either goes constantly low or constantly high with small glitches and there's no activity on any of the other pins. Sometimes there will be a small amount of activity for a second or two and then nothing. After repeated resets it will suddenly spring to life and behave normally.

Once the machine is booted it stable, which suggests the reset circuit. I wish I knew where it was and what components it used.

[stephen_usher]

Another strange thing I noticed last night was that the 486DX2-66 is actually running at a third of the speed of 486DX-33 for some reason. :-/

[rubber_jonnie]

Another strange thing I noticed last night was that the 486DX2-66 is actually running at a third of the speed of 486DX-33 for some reason. :-/

This one is certainly giving you the run around!!

[stephen_usher]

Yeah. I'm not sure that it's worth much more work unfortunately as it seems to be degrading with every minute of run time.

I could replace all the jelly bean tantalums on the board and hope that it fixes things but there's no guarantee. If it is a tant then I just wish it'd die in a blaze of glory and get it over with.