First post, by Meoseko
Dear VOGONS people, I come in the need of help.
I've been lurking these forums for the past couple months, mainly through google search results when trying to find solutions for various problems while building some old PCs.
Eventually, both of my machines were in a satisfactory state, at which point something in the floppy drive of my DOS machine fizzled, rendering the machine dead. Since then, I've been trying to figure out what parts of the machine were affected by that in an effort to get everything back to how it was. Here are the specs of the machine in question:
Motherboard: MB-8500TVX-A Ver 2.3 (Including a mod to socket the Dallas RTC for easy swapping as well as a battery holder)
CPU: Intel Pentium MMX SL27S
PSU: AT
RAM: Unsure since it came with the original MB but here is a picture.
GPU: Matrox 618-02 REV: A (MGA-MYST/21)
Of course the PC also has hard drives, a sound card and a 3.5" disk drive as well as a CD drive, but since the problem persists even if I remove all of these things, I would already be happy in getting the pc to turn on without having any of these hooked up.
Originally I only ordered a new motherboard, but when taking out the CPU of my old motherboard to put it into the new one, I noticed that it had several spots on it that looked like it had popped there. So, I ordered a replacement for that CPU as well, put that new CPU into the new motherboard along with the RAM and GPU from the old motherboard, configured the jumpers on the motherboard just like on the old one and hooked that up to my old PSU.
Now, here is where I'm at a loss:
Before that floppy drive mishap, the PC started without any problems.
Now, however, the PC only turned on after several attempts. If it wouldn't turn on, there were no beeps, no picture. The hard drives and CPU fan would spin up, the CD drive would be able to pop in and out, but that's it. After several more attempts, the PC would turn on with a picture, but the system would freeze before it counted up the RAM. (The RAM count showed something like "KB 0 KB".) After restarting once more, it would then boot into DOS just fine and run well through several games and restarts for well over 6 hours.
On the next day, same deal. Had to try a while before it would turn on. On the first turn on, it would freeze while I was in the Bios and after a restart, it would work fine for the rest of the day.
Today, it wouldn't turn on at all, no matter how often I tried.
My biggest hunch is that the CPU jumpers seem to not be configured correctly, but I didn't question it since the old one ran like this and this one also seems to sometimes run like this, and I just don't know any better. Here is what I've been able to gather about that:
Here's the manual: https://stason.org/TULARC/pc/motherboards/B/B … Pentiu-211.html
Here's the cpu: http://www.cpu-galerie.de/html/intelpentiump55-fv233.html
My jumper configurations are:
Flash Memory Voltage: +12V type Flash Memory used (Other option, +5V) (JP3: 2-3 Closed)
Cache RAM: 512 KB Cache RAM size (JP7: Closed)
CPU Voltage: Doesn't look like a valid setup in the manual, but that's how I got the original board and it ran that same model CPU like that. The two options here are single voltage or dual voltage, either selected by JP6 1- 2 Closed + JP11 1-4 Closed or JP6 2-3 Cosed + JP11 1-4 Open. My setup is JP6 2-3 Closed, JP11 1-4 Closed. Possible cause of error?
CPU I/O Voltage: 3.5V (other option: 3.45V) (JP12: Open)
CPU Voltage Select for dual Voltage CPU: 2.9V (other option: 2.6V) (JP14: Open)
CPU Clock Select: 100 Mhz (that's not what it showed when the PC was turned one as far as I know) (JP5: 1-2 Open, 3-4 Closed; JP8 Open; JP9 Open)
Now the CPU specs tell me the core voltage is 2.8V +- 5%, the I/O voltage is 3,3V +- 10% and it's also a dual voltage cpu. Wouldn't that mean these voltage jumpers are setup all wrong? Could this be the problem? If yes, why did this configuration work without problems with the old CPU/MB that were exactly the same model?
Last thing I tried was to put the RAM from slot 3 and 4 into 1 and 2 but that didn't do anything either. I hope it's just me setting up the jumpers in a configuration that supplies the CPU with so little power that it only turns on sometimes or something like that. Hope anybody has any ideas. Thanks so much in advance!