This looks more like your motherboard: https://stason.org/TULARC/pc/motherboards/F/F … -GVT-REV-A.html

Normally, the board should still be able to POST, even without a battery. What you described, I have come across on one of my 286 motherboards where the board simply refused to POST without a functioning on-board battery (this one had the DALLAS RTC).
A couple of things to perhaps verify:

• Make sure that you don't have any jumpers set to "Clear" CMOS. Based on what I can see, jumper J2 must have pins 1-2 closed for external battery operation. 3x 1.5V (i.e., 4.5V) should be fine for a 486 motherboard but, 4x 1.5V (i.e., 6V) should be fine as well. The external header usually has a diode in place to prevent charging of the external battery, which then also causes the output voltage to drop (on average, about 0.6V).
• Make sure that your CPU jumper settings are correct. Considering that you linked to the incorrect motherboard in your first link (I didn't check the pdf file), your jumper settings might not be correct and therefore, the board won't POST. Do you have a Cyrix 486DX-40 or an AMD 486DX-40? For the latter, use the same jumper settings as with the Intel (non CX CPU type).
• This board does appear to support both 30-pin simms & 72-pin simms to be populated at the same time. However, you need to populate all the sockets in bank 0 (the 30-pin simms) if you wish to use that bank.
• You might have a corrupt BIOS but, first try out the above before considering this as being the fault.

Does the Bios Rom belong inserted like that in the back of the dip socket?

jesolo wrote:

This looks more like your motherboard: https://stason.org/TULARC/pc/motherboards/F/F … -GVT-REV-A.html

Oops, in my haste I linked the wrong board. No, definitively using the correct jumper settings, the PDF describes the correct board. 😀

One of the things I noticed with this board is that it doesn't always marks pin 1, e.g. JP1 & JP2 have no pin indicators near them. I am assuming that pin 1 is the one closest to the jumper label?

With the ram, OK, I will try to populate all 4 slots in bank 1. I don't think this is a requirement for the 72 pin slots, right? I.e. both those are marked individually as bank 2 and bank 3, so from that I assume that when using 72 pin memory that at least only bank 2 has to be populated (not both as a requirement).

The fact that the BIOS sticker seems to be tampered with worries me a bit though. Which leads to:

Nvm1 wrote:

Does the Bios Rom belong inserted like that in the back of the dip socket?

Interesting observation. I hadn't noticed this yet. I've checked and there are no "dangling" feet, but, yeah, kinda odd. I purchased this board under the condition that it works so I assume that the BIOS is inserted correctly. However, maybe it died in transit...

I'm using an AMD 486DX-40. 😎

Haven't had time to test anything but I realised that, in case the BIOS turns out to be bad, I do have another 486 motherboard that has battery damage with a very similar BIOS on it. Both board are AMIBIOS 1993. The only difference is that this board I'm trying to POST, the BIOS serial starts with AA and the other BIOS I could fallback on starts with AB.

Would these BIOS'es be interchangeable by any chance?

Nvm1 wrote:

Does the Bios Rom belong inserted like that in the back of the dip socket?

This most likely because the motherboard can cater for either 28-pin DIP E(E)PROM or 32-pin DIP E(E)PROM.
I've seen this in many cases with SRAM cache modules - based on what I've seen there, the ROM is always placed at the "back of the DIP socket".

I just noticed in the manual that the BIOS supports both AMI (28 pin) and Award (32 pin) BIOSes (JP7).

pan069 wrote:

One of the things I noticed with this board is that it doesn't always marks pin 1, e.g. JP1 & JP2 have no pin indicators near them. I am assuming that pin 1 is the one closest to the jumper label?

Not always. Perhaps refer to the pdf manual to see if it indicates which pin is pin 1.

pan069 wrote:

With the ram, OK, I will try to populate all 4 slots in bank 1. I don't think this is a requirement for the 72 pin slots, right? I.e. both those are marked individually as bank 2 and bank 3, so from that I assume that when using 72 pin memory that at least only bank 2 has to be populated (not both as a requirement).

Actually (based on the link to Total Hardware 99), bank 0 is the 4 slots for your 30-pin simms, which must always be fully populated (since 30-pin simms are each 8-bit in data width x 4 = 32-bit). Bank 1 and Bank 2 is each of your 72-pin slots and you only have to populate either one of the two (since a 72-pin simm is 32-bit data width).
Although the manual states that you can populate both bank 0 & bank 1/bank 2 simultaneously, I would populate either bank 0 or bank 1 first (i.e., don't populate both at the same time) to see if it isn't perhaps a memory issue with the motherboard.

pan069 wrote:

Haven't had time to test anything but I realised that, in case the BIOS turns out to be bad, I do have another 486 motherboard that has battery damage with a very similar BIOS on it. Both board are AMIBIOS 1993. The only difference is that this board I'm trying to POST, the BIOS serial starts with AA and the other BIOS I could fallback on starts with AB.

Would these BIOS'es be interchangeable by any chance?

In some cases it might work but, not always. If the chipsets between the two are not the same, chances are it won't POST but, even if they are, there is still no guarantee it will POST (speaking from personal experience).
Best would be to try and obtain a copy of the original BIOS - anyone that has a similar motherboard can extract the BIOS for you with a utility called Navratil System Information (NSSI 0.60). They must just ensure that the BIOS is loaded with its default settings with no BIOS ROM being cacheable. You then just have to burn the image to (most likely) a 27C512 EEPROM (64 KB). If you don't have an EEPROM burner, then I'm sure there should be people in your area that could assist.

Great. Thanks for the help, much appreciated. The manual does indeed out lines which pins are "1". Luckily this manual exists. 😀

null

Anders- wrote:

Is your Am486DX-40 an SL-enchanced cpu? The RN-configuration visible on the photo indicates that? Got the same board myself.

I don't believe so, this my CPU:

@Anders, by the way, I might have to grab a BIOS image from you in the future 😀

I've got the same board as well. Apparently there was an Award BIOS on a 28-pin chip too.

Also, I'm running mine with a CR2032 hooked up to the external battery connector and it works fine. It does POST without the battery, but gets a little weird sometimes (for example, deciding that my DX2/66 is somehow 75HMz...

null

Anders- wrote:

Edit: sorry for thread hijack, though the topic is somewhat related + the op got a free thread bump 😁

🤣. No worries! The more we share, the more we care, or something like that 😀

Personally I had not considered running anything faster than a DX2-66 on this board, I have better boards for a DX4-100. I only initially tried with a DX2-80 to test if my DX-40 might have been faulty. According to the specs to should be able to take it.

Haven't had time to do any more tests though, probably has to wait to the weekend... 😢

Could it be that this board does not support AMD CPU's?

pan069 wrote:

Could it be that this board does not support AMD CPU's?

Highly unlikely. AMD CPU's at that time were basically just clones of the Intel CPU's. And, this motherboard also supports the Cyrix CPU's.

I suggest just confirming your jumper settings again. Otherwise, probably a faulty BIOS ROM.

As a last resort, try disabling the on-board cache memory and see if that perhaps makes a difference.

OK. It's working!

I took some time and went through all the jumper settings. One thing to pay close attention to was the fact that the board can have 2 different chip sets, mine has the VIA chipset and for my 40Mhz CPU I had to follow the jumper setting for that chipset (obviously).

One thing I do not fully understand though; if you look at the PDF manual I initially posted, under the speed settings (under VIA VT 8225), there are two options for 40 Mhz (this is a single page link):

http://www.peters-paradise.org/Fotos/Archivie … ual/JUMPER4.PDF

Further more, I tested 16 megs of 30 pin ram in bank 0 which got all detected. However, every 72 pin FPM module I tried in bank 1, only half of it was detected. So, sticking 8 megs in there would come up as 4 megs and 32 megs would come up as 16 megs, etc..

I might need some more research on that bit, but at least I now know that the board works with the CPU I want on it.

Thanks to everyone chipping in info, much appreciated!

I recently came across the same mobo, but the GAL chip at socket U2 is missing.

If possible, can anyone provide the file (usually .jed) for flashing a new GAL (and hence possibly reviving the motherboard)?

Thank you in advance.