wbahnassi, your motherboard tries to boot with prompt to enter BIOS settings because of non-working videocard error. That's why you hear 2 more short beeps after the Award BIOS sound error pattern for videocard problem (1 long + 2 short beeps) and some "interval" of silence.

One short beep is when mobo POSTs normally (without errors) and it's weird to hear this when there's still non-working videocard.

As for the BIOS strings - you have to merge (deinterlace) the low + high dump files into one file and then you can see all the strings in the BIOS with any hex-editor.

wbahnassi wrote on 2025-07-02, 16:56:

[*]MDA card (8-bit) - No progress

So you did try a dumber card and it still didn't work. Then I guess there might be some damage. Things to try:
- Connect and use RESET button, in case the mobo doesn't init properly for some reason on power-on.
- Make sure the 146818 RTC chip is getting power from PSU, if there is any battery corriosion in that area it migt be unpowered and that will cause havoc.
- While testing the RTC see if you can draw some basic schematic of the connections to the battery header. Some of these mobos require a jumper for external battery for example. IIRC I once ecountered a mobo that needed it for the on-board battery as well, except on different pins. But missing jumper should not prevent the RTC chip being powered from PSU.

And finally there is usually ALS245 chip near the ISA slot and the RTC and KBC. It's a bi-directional driver for the lower 8 bits of the ISA bus, and it often dies (usually not completly, one or more bits get weak or stuck). This will prevent the mobo from being able to talk to any of the cards, and even detect the video memory. You might want to desolder it and put a socket there. If the chip is good it can be socketed, if not you can replace it with ALS or ACT series. Note it's sometimes very hard to figure out the bad data bits if the output is just weak, so consider the socket if you don't fancy in-depth logic probing of the ISA signals.

wbahnassi wrote on 2025-07-02, 16:56:

What tool did you use to extract that string? Looking straight at the files in a basic binary viewer didn't yield anything human-discernible to me.

Chipset on these mobos is not all that advanced, it's basically just a bunch of PLDs with a lot of pins to handle all the busses and signals. So there is no ROM shadowing and EPROMs are slow, so for 286 you want at least to make up for it with 16-bit wide data. So each of the BIOS ROMs is one byte wide, the EVEN is bits 0-7 (so bytes 0, 2, 4, etc) and ODD is bits 8-15 (bytes 1, 3, 5, etc). To get proper ASCII strings you need to combine both dumps to get what the CPU actually sees. I've attached the result of that in the previous post.

Okaaay, so.. then does that mean I need to reverse this BIOS interleave process before I burn the ROMs? Because so far I have been just downloading BIOS files that have LO and HI parts and directly write each to a chip.. but many other ROMs came as one combined file.. so I need to split that or what? And what tool do I use to split it?

wbahnassi wrote on 2025-07-02, 22:59:

does that mean I need to reverse this BIOS interleave process before I burn the ROMs? Because so far I have been just downloading BIOS files that have LO and HI parts and directly write each to a chip.. but many other ROMs came as one combined file.. so I need to split that or what? And what tool do I use to split it?

Yes, if you get an image obtained via software read, or an alaready combined file for whatever reason, you need to split it to EVEN/ODD byte parts to burn it into EPROMs. These mobos would always have 2 EPROMs so there should be two files, but some newer 286 mobs (with 20MHz+ CPUs) will have chipsets that are more like 386SX. Can do shadowing and address more than 4MiB of RAM - so the BIOS ROM will be just one chip, and thus one image file. But good chances are these will not be compatible with this early Suntac "chipset". But you can try splitting it and burning anyway.

What tools to use, well I just wrote my own scripts in Python. Back in the old days I would use QBASIC for that.

wbahnassi wrote on 2025-07-02, 22:59:

Okaaay, so.. then does that mean I need to reverse this BIOS interleave process before I burn the ROMs? Because so far I have been just downloading BIOS files that have LO and HI parts and directly write each to a chip.. but many other ROMs came as one combined file.. so I need to split that or what? And what tool do I use to split it?

I wrote one recently, 'cause I needed something convenient with basic checks for ROM-dump files it processes. Just uploaded DOS and windows versions here: A simple BIOS ROM-dump interlace splitter, deinterlace merger and slicer

Hello retrocomputing experts!
When I turn on the motherboard, the image I uploaded appears, stating that the configuration is incorrect. When I run the SETUP program, I get the image I'm showing. No matter how many times I change the configuration, I get an error message about an invalid CMOS memory size. After rebooting, the error reappears, but the configuration remains the same.
This has been happening to me since I mounted the motherboard inside a PC case. I've made sure the motherboard isn't touching any metal in the case; it has plastic spacers.
It's a MIATA BAY-1000C motherboard.
What could it be?
Thank you very much.

dennisE wrote on Yesterday, 06:16:

When I turn on the motherboard, the image I uploaded appears, stating that the configuration is incorrect. When I run the SETUP program, I get the image I'm showing. No matter how many times I change the configuration, I get an error message about an invalid CMOS memory size. After rebooting, the error reappears, but the configuration remains the same.

What battery do you have connected there? Some mobos are jumpered for external pack, or require a specific jumper setup for that, get it wrong and it might leave RTC/NVRAM completly unpowered. Could be also copper damage from on-board NiCD spill. Please provide some photos of the mobo, and if it works outside the case then surely something must be either shorting out or the power problem simply gets worse with more grounding points.

I got the very same motherboard last year like @predator99 has. The "E" picture he posted.

Predator99 wrote on 2019-09-05, 22:04:

The attachment SUNTAC_2019-09-A.jpg is no longer available

The BIOS appears to be Award 3.03, dated in 1985 i think. The chipset is SUNTAC ST62C006. Going through different manuals, there is no JP3 and JP1 present, so i don't know how this options are hardwired on this board 🙁. So BIOS speed setting doesn't work. The TURBO switch button is the only thing, that changes the speed from 6 to 12MHz. Also tried with "Ctrl Alt +" and "Ctrl Alt -" as stated in two manuals, and that doesn't change motherboard speed. When I press the turbo switch, also turbo LED light's up. I checked up the CPU frequency in CheckIt 2.1 benchmark.
It is strange, why there is speed setting in BIOS while it doesn't work. Maybe because BIOS is generic across multiple 286 boards?

Also I have another strange behavior (or is it common?). The only ISA VGA card that works on this board in 6 and 12 turbo speed is Cirrus Logic GD5422. The graphic card has no jumpers or any settings - also the card chip is dated 9246.
Another VGA card i tried is OAK OTI067, it works only in slow 6MHz, when i toggled PC to TURBO 12MHz, the graphics cripples, and the PC speaker makes one beep and freezes.
I tried OAK OTI037C, cripples on the startup - it starts with colorful "Copyright something and few characters" and freezes (in slow and turbo mode).
I tried two different TSENG ET4000AX card - nothing shows on the screen.
I also tried TRIDENT TVGA9000C - monitor shows something like out of range...

All VGA ISA cards I mentioned, work on 386 PCs. Is it maybe something wrong with my 286 mobo? What else should I try? If you need maybe more infos or photos, let me know.

Please excuse me for double posting.
An update to my previous post:
I tried all of the ISA VGA cards on another machine - ASEM DESK 5011 - it has its own 286 motherboard with CHIPS chipset and 10MHz fixed frequency. All of the above mentioned ISA VGA cards are working and booting.
So there must be something wrong with the original mobo 😒

Hi Deunan, here's a photo of the motherboard. It was modified to install a CR2032 battery. Could it be that the CMOS is corrupted? What jumper is used to reset the CMOS? Kind regards.

80286 ? Why ?
Is it better than AM2900 bit-slice CPU ?

dennisE wrote on Yesterday, 15:33:

Hi Deunan, here's a photo of the motherboard. It was modified to install a CR2032 battery. Could it be that the CMOS is corrupted? What jumper is used to reset the CMOS?

I'm not a big fan of CR2032 mods on these old mobos. This works well with Pentium era stuff and newer, also some later 486 mobos, but this one has a 146818A RTC/NVRAM chip. It's CMOS, sure, but still pretty power hungry. That battery won't last, and the voltage is 3V rather than 3.6V of the NiCD. That might seem like small difference but one diode forward drop and the voltage gets below what the datasheet wants. In general on mobos where the RTC is already a part of the main chipset rather than external part you can try a CR2032 approach. With good old 146818 that's just not enough.

On many early mobos the CMOS clear jumper, when moved, will simply disconnect battery power from the RTC and ground the pin, that's it. Obviously it cannot be done with the system powered or it cause a short (there sometimes is a small resistor to protect from such mistakes, but not always present). Depending on how this battery mod was done there might not be a way to clear the CMOS now, other than removing the battery and shorting the socket pins for a moment.

Do you have a volt meter? You can check the voltage on pin 24 (the last one) with the battery and while powered by PSU. With PSU it should be more than 4V (about 4.5V) and on battery you'd want at least 2V. But that is already too low and that particular chip might require 3V or more. Consider 3x AA (or AAA) pack as external battery for this mobo, that's what I use.

yugokoral wrote on Yesterday, 13:35:

It is strange, why there is speed setting in BIOS while it doesn't work. Maybe because BIOS is generic across multiple 286 boards?

Yes, quite a number of these mobos were clones (of clones). Could be the BIOS is "borrowed" too, after all why pay the fees when you can just copy it. Or somebody might have tried a different BIOS, or repopulated mobo's missing chips with what was on hand. Hard to say after all these years. So it could be blocked by some jumpers (perhaps soldered permanently) or simply BIOS not 100% matching the mobo.

As for VGAs, these mobos are picky. Try all slots, especially the first and last ones, you might find the card work better in one of those rather than middle slots. For some reason these boards don't have the resistor packs that pull-up/terminate the ISA signals and that affects middle slots the most. Also the cards should not be using ALE signal, the memory refresh cycles on these mobos often generate ALE glitches and this prevents the cards from working. You can figure out which card is not using ALE looking at the edge connector - the pad will be missing or unconnected.

dennisE wrote on Yesterday, 15:33:

It was modified to install a CR2032 battery. Could it be that the CMOS is corrupted?

My 2 pennies on your 286 motherboard CR2032 battery modification:

It's not so trivial thing. Some of those mobos use rechargeable external batteries. Probably CMOS is not corrupted, but your CR2032 battery can't provide enough voltage to RTC+CMOS chip due to forward voltage drop of the diodes used in the circuit - just like in my case with a similar 286 Suntac based mobo from the linked thread.

What I can see from your picture is that someone just soldered CR2032 battery holder in place of the original rechargeable NiCd barrel battery - and that's it, which is far from enough. And of course the charging line is not cut off, which will cause even faster degradation of non-rechargeable CR2032 battery. You'll have to remove one diode (or one resistor) and replace another diode to one with lower forward voltage drop to make this modification proper.

There are some pins next to the battery holder. Could they be for connecting an external battery?

dennisE wrote on Today, 06:53:

There are some pins next to the battery holder. Could they be for connecting an external battery?

Probably they are. And this does not exclude the possibility, that the ext. battery header is not connected in parallel with original NiCd battery terminals i.e. it still needs an external rechargeable battery pack. See the link (and the thread) I gave you in my previous post.

I've checked the battery voltage and it's fine. I think the problem is with the CMOS chip. It saves the configuration correctly, but there's some incorrect information, and when I turn on the POST, I get an error message about the configuration. Do you have any ideas on how to fix this?
The CMOS chip is the HD146818P? Could it be that the memory is failing? How can I check for certain? Thank you so much for the help.

dennisE wrote on Today, 08:54:

I've checked the battery voltage and it's fine. I think the problem is with the CMOS chip.

You should check at pin 24 of the RTC chip directly, rather than the battery. These have Power Sense (PS) pin, if it gets too low a bit will be set in the chip - BIOS checks it and will consider the contents of the NVRAM invalid (even if it appears OK) when it's set. This is done to prevent brown-outs from introducing bit glitches into the NVRAM, which is exactly what might be happening with your battery mod.

But yes, the chip can be the problem too. Perhaps it can be replaced with a bit more modern one that will tolerate lower voltages in general (better CMOS process). On your mobo it's HD146818, close to power connector, but it looks to be soldered rather then socketed so you'll have to desolder it. Preferably put a socket there to make the swaps easier. Look for replacements using just the number, because the HD part is manufacturer-dependent, originally it was Motorola I belive and started with MC.

How do I check the voltage at pin 24 of the HD146818? I understand that I connect pin 24 on one side of the tester, and the other side (battery or power supply)?

If I put in an external battery, for example, 3.6V, will it be enough to work?

Thanks very much!

Deunan wrote on Yesterday, 22:38:

yugokoral wrote on Yesterday, 13:35:

It is strange, why there is speed setting in BIOS while it doesn't work. Maybe because BIOS is generic across multiple 286 boards?

Yes, quite a number of these mobos were clones (of clones). Could be the BIOS is "borrowed" too, after all why pay the fees when you can just copy it. Or somebody might have tried a different BIOS, or repopulated mobo's missing chips with what was on hand. Hard to say after all these years. So it could be blocked by some jumpers (perhaps soldered permanently) or simply BIOS not 100% matching the mobo.

As for VGAs, these mobos are picky. Try all slots, especially the first and last ones, you might find the card work better in one of those rather than middle slots. For some reason these boards don't have the resistor packs that pull-up/terminate the ISA signals and that affects middle slots the most. Also the cards should not be using ALE signal, the memory refresh cycles on these mobos often generate ALE glitches and this prevents the cards from working. You can figure out which card is not using ALE looking at the edge connector - the pad will be missing or unconnected.

Thank you for more info, Deunan.
I am always trying in the first slot, also I tried in other slots. I did check for ALE B28 pin, and as i can see, the Cirrus Logic card GD5422 is using that pin, which works perfectly fine on this mobo. But TSENG ET4000AX, is also using that pin, and there is black screen. The OAK OTI037C is not using B28 ALE pin at all, but also glitches when mobo powers up. So I think that the culprit is something else.