First post, by FidoMike
Hello all, I am having an odd issue with two Pentium boards that I am totally stuck with. Really hope someone can help with this.
I have a DEC Venturis 575, from what I can tell the model number means 5 for pentium and the rest is the speed of the included processor, therefore it should be a Pentium 75 which the BIOS confirms.
On power-on, it complained of a dead CMOS battery, it has a socketed Dallas DS12887. It wanted me to replace and enter the BIOS and correct the values etc. Before replacing the RTC, I tried anyway to get it to do anything, I wanted to hook up a CD ROM and / or an 120GB HDD, on trying to detect either of these, the BIOS would just hang. I Initially thought it was just an old BIOS and those two drives might be too new, so I didn't worry much. I took those out and tried just a floppy drive, the drive that came with the PC seems to be faulty, so I swapped it out for another I know works.
I put in a Windows 98 boot disk that I use it for loading CD drivers etc for DOS games, the disk works in other PCs but on this board it seems to read the disk, I can hear 2 sets of the normal floppy access sounds, then a load of symbols and what looks like a part of exe file is dumped to screen and it stops. Very much like if you were to try to print out an exe file. The only words are 'FAT12' repeated several times. Oddly it hasn't frozen, a Ctrl + Alt + Del will reboot it. At this point I thought it was the disk gone bad, so tried an other, same problem. I then tried same drive and disk in an other PC (a DEC 486) and it was fine with it. I then assumed it was due to the Dallas RTC, and therefore ordered a new one from RS online. I replaced the DS12887 with a DS12887+, powered on, entered BIOS, loaded defaults with F9, saved it. Tried to boot, it no longer complains of dead CMOS battery, seems to hold the time fine, but it wont boot, same mess on screen as before. I also tried detecting the HDD or CD drive again, and it still hangs.
I tried lots of different things in the bios settings, disabled shadows/caches or anything it offered, I also discovered that the 'F9' load defaults only applies to the page currently displayed, so I even tried going to every page and every sub page loading defaults and saving. I even tried swapping the floppy drive to the end of the cable, it didn't like that, but when I told it to swap the drives, it seemed to accept it, but again none of these made any difference. I did also try the 'clear config data' under the advanced / plug n play area. Still nothing.
At this point I was starting to think the board was dead, so I took out the floppy drive, and its cable, put that into the DEC 486, and it worked fine. I then put the drive and cable back in the pentium, disconnected its power supply and used the DEC 486's one, still same mess on screen and no boot. I tried removing the risa card, swapping the CPU for a pentium 133 I had separate, still same.
I was now convinced it was a board problem, so I went on eBay and got a used but tested replacement, same part number as my existing board. I was pleasantly surprised it came with CPU and 40MB RAM. I decided to not do anything to it, and put the board in exactly as is with the CPU/RAM. It powers on, BIOS says its a Venturis 5120, and confirms a Pentium 120. It complains of dead CMOS battery, ok not unreasonable, and I have to load defaults in BIOS, and try to boot. Same output as before, corrupted mess with the FAT12 being only item recognisable. To be clear, I did not try replacing the Dallas chip on this board.
As this looks like the same issue as my original board, I then went back to my original and tried the password clear jumper, usually when I try these the boards wont post until it is removed again, but this started up with no change. I tried the jumper next to it which said something on the lines of recovery, this appears to be a BIOS recovery/flash feature, nothing on screen and tries to access the floppy. I stopped at that point as I don't have a BIOS floppy for it. I even tried the mysterious 'FACTORY SETTING' jumper near the AT power connector, seemed to do nothing, even after putting it back.
So in summery, two boards, both have this odd problem, and I think I have tired everything I can think of on the original board. I haven't done much on the replacement, as it seems to be an identical issue, and I don't want to do too much as it might get returned. I say might, as the price I paid for it, I might keep it for the RAM and CPU regardless of the board.
Any help or ideas would be very greatly appreciated.