Finally got the board to boot. It originally had an unknown upgrade processor (QFP on adapter with glued on heatsink and identifying labels removed by previous owner). The jumpers were not set for any known 486 clone. I replaced it with a working 486DX4-100 &EW. It still wouldn't boot.

Today I looked at all the jumpers, and found one that doesn't have an identifying mark on the board and is not mentioned in the partial manual I found or on any website I found. I removed that, and it booted! I feel a right fool, I'm guessing I had been trying to boot with the Clear CMOS jumper closed for the last few weeks 😀

Going to give up for the day as soon as I test it with the Cyrix chip. Tomorrow I will install Windows 95 to make sure it is stable.

Fingers crossed 😀

It has POSTed, so should be alright. I will install Win 95 tomorrow and check the revision. Might run SuperPi before I ship it back 😀

Great! Stepping/revision can be checked from DOS with the IBM utility from this thread: Cyrix 5x86 Register Enhancements Revealed

debs3759 wrote:

Finally got the board to boot. It originally had an unknown upgrade processor (QFP on adapter with glued on heatsink and identifying labels removed by previous owner). The jumpers were not set for any known 486 clone. I replaced it with a working 486DX4-100 &EW. It still wouldn't boot.

Interesting... so it didn't boot with original settings with the mystery CPU? Makes me wonder if that thing was something very exotic that died, or if it was just a mess-up by the previous owner...

In any event I'm curious about that thing. Do you have photographs of it?

dionb wrote:

debs3759 wrote:

Finally got the board to boot. It originally had an unknown upgrade processor (QFP on adapter with glued on heatsink and identifying labels removed by previous owner). The jumpers were not set for any known 486 clone. I replaced it with a working 486DX4-100 &EW. It still wouldn't boot.

Interesting... so it didn't boot with original settings with the mystery CPU? Makes me wonder if that thing was something very exotic that died, or if it was just a mess-up by the previous owner...

In any event I'm curious about that thing. Do you have photographs of it?

I suspect it was a duff processor, but will at some point do some more testing.

No photos yet. I will take pics of the 5x86 (front and back) when I remove it from the board. I'll take a pic or two of the board as well.

For tests, I won't do anything too intensive, as it's not my CPU, but I do intend to run SuperPi 1M (32M might take a week, so won't try that). All the owner and buyer have asked for is a quick check of what stepping and revision it is.

It is guaranteed to be Stepping 0, Revision 5. I assume you will be installing Windows 95 with the Cyrix 5x86-133 installed?

feipoa wrote:

It is guaranteed to be Stepping 0, Revision 5. I assume you will be installing Windows 95 with the Cyrix 5x86-133 installed?

Yes. I'm going to take advantage of the extra speed for installing 😀

Did you set the voltage to 3.6 V? You'll want to ensure you aren't running it at 4 V or 5 V. Some of 3.45V chips will appear to work with 4V or 5V, but I don't suspect they will last for very long.

It's set to 3.45V. I only have settings for 3.45 and 3.6 on this board.

Hmmm... I too noticed that the manual doesn't show a 5 V setting. I sorta recall some of these mid-90's Asus boards doing some kind of auto voltage selection, perhaps based on the CPU jumpers or CPU identification. I would ensure that JP18-JP24 are set appropriately for the Cx5x86.

The jumpers are set right. I used the table at http://gboeger.de/Computer/Asus_PVI486SP3/pvisp3-cpu.html to get the settings. I only booted as far as the BIOS / POST screen earlier, but it was correctly detected.

I need to find a DX-50 so I can test for undocumented clock speeds. I'm hoping to find FSB settings from 16 to 66 MHz. Only 25 to 40 are documented. I have so many CPUs that I haven't recorded yet in my database, that I probably have one somewhere 😀

Hoping that I have a nic that Win 95 has drivers for, so I can get online with it (or at least see my main PC to copy the updated BIOS and a few other files).

If you are going to run it at 3.45 V and it doesn't install W95 properly, you could try 3.6 V, which is what the CPU is rated for.

Many PCI socket 3 motherboards used similar PLL clock generator chips, which generally run from 20-66 MHz.

Usually, network card drivers for W95 are small enough to fit on a single floppy diskette, so shouldn't be an issue either way. I think the 3Com Etherlink III (3c509b) drivers were included in w95c when I installed it.

Thanks. I just changed the voltage setting.

I didn't get anything done today (that's not unusual for me). Got a CT2230 (SB16) Revision 49432 (the latest and best revision) to add to the system. I have visitors Sunday PM, but hope to be up to working on it in the evening.

This hasn't been my smoothest system setup. I have DOS and WFW 3.11 installed, that part was easy. Waited three weeks for a USB floppy drive that I ended up having to get a refund on as it never arrived. I needed that to transfer CD and network card drivers, so I can install Win 95. I ordered another today from a much more reliable seller (200K/100% positive feedback on a populat auction site), that should arrive Tuesday or Wednesday. Then got given an early socket A system with nic and fdd!

Long story short, that now has XP installed, and is ready to connect to the network in the morning, so I can copy the necessary file to floppy and finish setting up the PVI-486SP3 system (including Win 95 upgrade).

By tomorrow night, the 5x86 will have been tested. Only minimal testing, as it is not my chip to overclock or stress test 😀

Once the testing is finished and I have one of my own CPUs in it, I will be setting up a dual boot system with DOS 6.22, WFW 3.11 and Win 95 OSR 2.1 (if anyone know where I can get an OSR 2.5 original disc, please let me know). Got to set up an original 95 boot disc to help with setting up the dual boot.

feipoa wrote:

It is guaranteed to be Stepping 0, Revision 5. I assume you will be installing Windows 95 with the Cyrix 5x86-133 installed?

Yes, it's Stepping 0 revision 5.

I used it to install DOS, WFW 3.11, drivers then Win 95, as well as the obligatory BIOS upgrade to 3.07 (beta with year 2K support). I kept 95 running for 24 hours, and everything looks good.

I'll be removing the Cyrix 5x86 later and probably replace with an AMD 5x86 P75 until I'm ready to bench my 486 collection.

Curious if you also tried it at 3.45 V?

No. As it's not mine and is worth a lot, I have kept everythink stock. Now if hard1k said he wants it optimised and to run SuperPi 1.5, that would be different 😀