skel2raw wrote:

Hi guys, I just found this asus motherboard in an old storage and somehow cannot get it to work. Maybe one of you has an idea wh […]
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Hi guys,
I just found this asus motherboard in an old storage and somehow cannot get it to work. Maybe one of you has an idea what could be wrong?

So I have installed an Intel i486 DX2 66 Mhz and set the jumpers according to the manual I found on phils homepage. When I try to boot it up most of the time nothing happens except for a black screen. Sometimes the pc speaker makes a long beep and boots up. However it wont boot properly and shows either "Unknown-S cpu" or a cpu with 16 Mhz and wont boot further. I also cannot enter the bios.
I have tried other 486 dx2 66 cpus and also and intel overdrive dx4 100, however the result is always the same as described.

Do you guys have an idea what could be wrong with the motherboard? Is it simply a wrong setting of the jumpers or is something broken?

Thanks four your help!

I have experienced this before.

1) make sure you have the correct manual and that the jumper settings are correct.
Most likely nothing is wrong with you cpu. Make sure you have known good working cards.
Only use a video card for now until you get it working.

2) put in a new battery

3) reseat your cache ram.

4) if still not working, the capacitors could be bad.

Thank you for the quick reply. I have already done that:

1) The manual is the correct one
2) I replaced the battery
3) I replaced the cache
4) I can only see one capacitor on the motherboard and it seems to be ok.

Any other ideas?

I am going to follow this thread because these are exactly the symptoms I had with my 486 motherboard.
After I reseat the cache ram it did boot to bios. But only once an now still does not work.
So I assume I have some bad cache ram or the capacitors have gone bad.

Somehow I managed to boot the motherboard up properly. I took all the chips and tried chips from other boards and now it boots up.

The only issue I now have is that I cannot update the bios. The flashtool tells me that the bios is write protected. Is there any way to disable the protection and flash a bios update?

skel2raw wrote:

Somehow I managed to boot the motherboard up properly. I took all the chips and tried chips from other boards and now it boots up.

The only issue I now have is that I cannot update the bios. The flashtool tells me that the bios is write protected. Is there any way to disable the protection and flash a bios update?

I had this problem too.
Some bios chips are only flash-able once. So you have to buy a NEW chip and flash it with a eprom reader.
And then insert it into the motherboard.
Or there are compatible flash-able bios chips available but you will still have to flash it with an eprom reader and then insert it into the motherboard.
Good luck on your journey.

I see... do you know an eprom reader you can recommend and how big does the eprom need to be?

TL866CS Minipro. Bought one myself about 2 years ago and cannot complain.
As Intel486dx33 has stated, most 486 motherboards does not allow you to flash the BIOS on the motherboard (this one included).
27C512 EEPROM is what you need for this motherboard (64 KB).
Also, take note that some of the jumper settings changed on this motherboard after some BIOS updates were done.
Double check your jumper settings to ensure it matches for the particular BIOS revision that you currently have.

your bios is most likely erasable by uv light, peel the top sticker off the bios chip and if there is a little round glass window it means its uv erasable rom. You need a uv eraser in that case and a external programmer

oh yeah don't forget to put the sticker back over the window, only take it off for erasing

Thank you guys! I just ordered the parts.
The only issue left is that the bootup screen shows the wrong CPU speed with the two CPU types I have. I hope this simply a jumper mistake and changes with the bios update.

no, that board normally uses the type of bios (has a window in the center under the sticker) that you need to erase using UV light, with a propper UV eprom eraser found on aliexpress.
i have 2 of those and i cant update bios because of that.
Updated bios supposed to take amd x5 133mhz

I see that but as jesolo mentioned, maybe the jumper settings changed and I am setting the jumpers based on another bios revision? Though this seems unlikely, at the moment I do not have any other idea what might cause show the wrong CPU speed. Any suggestions?

Although I'm sure the various BIOS revisions can be found all over the internet (and on Vogons as well), I've attached a zip file with all the BIOS revisions that were made available for this motherboard (I noticed that you never mentioned what your current BIOS revision is). Within the file called "sv2g0401.zip" is a text file which outlines the jumper settings for the new supported CPU's but, you can just refer to the jumper settings file called "sv2gx4 CPU jumpers.html" under the "Jumpers" folder, You can then compare those to your current jumper settings.

I have the bios version 0302. I just checked the jumper settings again according to the files you provided. No matter how I set the jumpers, my i486 DX2 66 is always recognized as a Dx2 with 32 Mhz. Any ideas?

skel2raw wrote:

I have the bios version 0302. I just checked the jumper settings again according to the files you provided. No matter how I set the jumpers, my i486 DX2 66 is always recognized as a Dx2 with 32 Mhz. Any ideas?

Technically, a 486DX2-66 has an external FSB of 33 MHz and an internal multiplier of 2. It's possible that your BIOS just displays the speed incorrectly but, it actually runs fine.
Best would be to test the speed of the CPU with a couple of benchmark utilities - try Navrátil System Information (NSSI 0.60): https://www.navsoft.cz/products.htm and run the CPU benchmark to see how your CPU compares with other CPU's. It might not be on par with the 486DX2-66 of what NSSI displays, since there could be other factors influencing the speed (wait states, cache & RAM timings, etc. on your motherboard) but, it should be very close to the comparative speed of NSSI's 486DX2-66.

However, your BIOS revision is a bit outdated. If the NSSI CPU & FPU benchmarks does show that your CPU is running fine but, you are still bothered by what it displays on the POST screen, then I would suggest you upgrade your BIOS revision. However, don't try and erase your existing BIOS chip. Buy a W27C512 EEPROM (electrically erasable programmable memory) and flash it with the revision 0402 BIOS. If you don't have access to an EEPROM reader, maybe ask around locally to see if someone can help you out. It's then just a matter of (carefully) removing the existing BIOS chip and replacing it with the one that you've flashed (taking note of the orientation of the chip).

PS: I have two of these motherboards and one has BIOS revision 0305 and the other one BIOS revision 0306. So far, I've been able to plug in an AMD486DX4-100 (NV8T) and the BIOS recognises the CPU without any problems. It shouldn't have any problems recognising a 486DX2-66 properly with BIOS revision 0305 or higher, since I tested a 486DX2-66 on my revision 0305 motherboard without any issues.

Ok, I'll do a benchmark and check the result.

To be honest, I do not think it is the bios version since the processor was already out on the market before the bios. Also I have a SVGOX4 rev. 1.5, which I believe is an earlier revision of the SV2GX4? It has the same bios version and shows the correct CPU speeds. Since I have no other clue what might be the source of showing the wrong CPU speed I simply hope a never bios version will resolve the issue...

skel2raw wrote:

To be honest, I do not think it is the bios version since the processor was already out on the market before the bios. Also I have a SVGOX4 rev. 1.5, which I believe is an earlier revision of the SV2GX4?

Yes, I believe so. The main difference (based on pictures I've seen) is that the VL/I-486SV2GO(GO4) has 4x 30-pin & 2x 72-pin simm slots, whereas the VL/I-486SV2G(GX4) has 4x 72-pin simm slots.

skel2raw wrote:

It has the same bios version and shows the correct CPU speeds. Since I have no other clue what might be the source of showing the wrong CPU speed I simply hope a never bios version will resolve the issue...

Based on what I've read, the BIOS revisions between the VL/I-486SV2G(GX4) & VL/I-486SV2GO(GO4) are interchangeable (at least up to revision 0305). You could try swopping the BIOS from your SV2GOX4 motherboard but, it will be at your own risk. I would rather burn a newer BIOS revision (you could even just burn revision 0305) onto a new EEPROM chip and see what the result is.

I already tried using the bios from the other board. Only after doing that the motherboard began to boot up properly. After putting the original bios back in, the motherboard kept booting up properly. The only issue left as far as I can see is the wrong CPU speed...

skel2raw wrote:

I already tried using the bios from the other board.

Did you experience the same problem with the CPU speed being displayed incorrectly when you swopped out the BIOS?

skel2raw wrote:

The only issue left as far as I can see is the wrong CPU speed...

Test the CPU with NSSI 0.60. If it runs fine, then I would try a BIOS update. If not, then either there is an issue with the motherboard or even perhaps the BIOS chip itself.

My understanding is that you've already tested the same CPU in the VL/I-486SV2GO4 motherboard and it did display correctly.
What happens if you install the BIOS from the VL/I-486SV2GX4 motherboard in the VL/I-486SV2GO4 motherboard? Does it also then display the CPU speed incorrectly?

Ok, I think I resolved the issue... I started NSSI, which properly recognized the CPU. When I did the benchmark the CPU performed slightly worse then a DX-33. When I realized this is a real-time benchmark, I thought I'll try connecting the turbo switch to see whether there is going to be a change. After pushing the turbo switch the CPU performed well above the benchmark DX-66 and also the post screen showed the correct speed at 66 Mhz!!!
Stupid of me not thinking about this earlier... I guess what irritated me was that it shows 32 Mhz instead of the expected 33 Mhz. I have no idea why that is but at least now I know the board seems to work properly.
Thank you for your help!!

Just two more things:
Do you know which cache chips I need to get in order to upgrade the board to 1MB chaceh?
Do you have an idea, where I can find information about how to set the pins for the LED panel of the case?