There have been numerous updates to the BIOS since the one you have. You will definitely want to update it. The file is attached. I know many of your have the UUD2012. I have updated this to UUD2014 just to remove the EDO RAM Read speed feature because it does nothing on this motherboard and only adds confusion.

Is your BIOS an EEPROM or UV EPROM? If needs to be an EEPROM to be flashed. Some common EEPROMs which work well on this board are PH29EE010, W29EE011-15, or AT29C010A for 5 V. Intel P28F001 for 12 V. Generally, I think most EEPROM's with 29EE010, 29EE011, or 29C010 will work. Given the revision of your board, I suspect it contains a UV EPROM. You will want to replace that with a flasheable EEPROM. I use a Wellon VP-390 to flash my BIOSes and test my SRAM.

Also, if the battery in your RTC is dead, which it most likely is, then you will not be able to boot the MB. This is because your CMOS settings aren't being saved. You can work around this to some extent by using MODBIN to save all the settings you wish in your CMOS, then flashing this new BIOS image to your BIOS chip. But every time you want to make any changes, you need to use MODBIN and reflash the BIOS.

The fact that your computer no longer shows any sign of life is a big concern and makes me question whether putting in the effort to desolder the RTC and flash the BIOS is worth it. Desoldering the RTC on this board is not fun. I would practice on some known dead boards first. If your ESCD is messed up, then you should try PCI cards which you haven't tried at all yet, such as the GF2.

I recommend a single stick of RAM for troubleshooting - 8, 16, 32, or 64 MB. Ensure that it is FPM and not EDO. Set the FSB to 33 MHz and the multiplier to 3x. Use an Intel DX4 or Am5x86 for testing. Ensure that you only have a graphics card installed and remove the HDD. Even remove the floppy drive - people plug these in backwards all the time. Use 256K of double-banked cache.

feipoa wrote:

There have been numerous updates to the BIOS since the one you have. You will definitely want to update it. The file is attach […]
Show full quote

There have been numerous updates to the BIOS since the one you have. You will definitely want to update it. The file is attached. I know many of your have the UUD2012. I have updated this to UUD2014 just to remove the EDO RAM Read speed feature because it does nothing on this motherboard and only adds confusion.

Is your BIOS an EEPROM or UV EPROM? If needs to be an EEPROM to be flashed. Some common EEPROMs which work well on this board are PH29EE010, W29EE011-15, or AT29C010A for 5 V. Intel P28F001 for 12 V. Generally, I think most EEPROM's with 29EE010, 29EE011, or 29C010 will work. Given the revision of your board, I suspect it contains a UV EPROM. You will want to replace that with a flasheable EEPROM. I use a Wellon VP-390 to flash my BIOSes and test my SRAM.

Also, if the battery in your RTC is dead, which it most likely is, then you will not be able to boot the MB. This is because your CMOS settings aren't being saved. You can work around this to some extent by using MODBIN to save all the settings you wish in your CMOS, then flashing this new BIOS image to your BIOS chip. But every time you want to make any changes, you need to use MODBIN and reflash the BIOS.

The fact that your computer no longer shows any sign of life is a big concern and makes me question whether putting in the effort to desolder the RTC and flash the BIOS is worth it. Desoldering the RTC on this board is not fun. I would practice on some known dead boards first. If your ESCD is messed up, then you should try PCI cards which you haven't tried at all yet, such as the GF2.

I recommend a single stick of RAM for troubleshooting - 8, 16, 32, or 64 MB. Ensure that it is FPM and not EDO. Set the FSB to 33 MHz and the multiplier to 3x. Use an Intel DX4 or Am5x86 for testing. Ensure that you only have a graphics card installed and remove the HDD. Even remove the floppy drive - people plug these in backwards all the time. Use 256K of double-banked cache.

Hmm, BIOS flasher is pricy - but there are people that can flash BIOS on-demand for only few bucks. So if i understand correctly, if i order AT29C010A chip and give them your BIOS file, it could work? Basically that will work the same as "CMOS clear" since this is completely new BIOS.

Found that chip on ali: http://www.aliexpress.com/item/AT29C010A/3262 … 24-c341d0fa32de

I think RTC battery is alive, when it was working it passed the ESCD section and shoved me the 'no boot media warning'.

Wait a second, if you have a UV EPROM, the system cannot write to ESCD anyway. When the BIOS writes to ESCD, it is actually writting the the flasheable section of the EEPROM. So your ESCD cannot be messed up. Please confirm that you have a little window on the top of your BIOS chip (UV EPROM).

I am not sure if swapping the BIOS chip will erase the data stored as part of the CMOS setup by the RTC. I think this information is somehow saved by the RTC module's battery. This is why it is usually recommended that after someone flashes to a new BIOS version that they go into the CMOS settings and select Restore BIOS Defaults or Load Optimal Configuration.

That jumper that you shorted should have cleared out your CMOS settings. You only need to short it for a second or two (or less). If the system isn't turning on, there could be many culprits, including, but not limited to, a bad BIOS chip. If I were you, I would pull out everything, short that jumper for 10 seconds, remove the jumper, plug in the GF2 or any old PCI card that you haven't yet tried, then fire it up. You could also have a problem with your VRM, in which case, try a 5 V CPU and jumper accordingly.

feipoa wrote:

Wait a second, if you have a UV EPROM, the system cannot write to ESCD anyway. When the BIOS writes to ESCD, it is actually writting the the flasheable section of the EEPROM. So your ESCD cannot be messed up. Please confirm that you have a little window on the top of your BIOS chip (UV EPROM).

I am not sure if swapping the BIOS chip will erase the data stored as part of the CMOS setup by the RTC. I think this information is somehow saved by the RTC module's battery. This is why it is usually recommended that after someone flashes to a new BIOS version that they go into the CMOS settings and select Restore BIOS Defaults or Load Optimal Configuration.

That jumper that you shorted should have cleared out your CMOS settings. You only need to short it for a second or two (or less). If the system isn't turning on, there could be many culprits, including, but not limited to, a bad BIOS chip. If I were you, I would pull out everything, short that jumper for 10 seconds, remove the jumper, plug in the GF2 or any old PCI card that you haven't yet tried, then fire it up. You could also have a problem with your VRM, in which case, try a 5 V CPU and jumper accordingly.

Yep, that is UV EPROM [foto attached].

The thing is - i never actually moved to the point of adding other hardware to the board. All my tests are performed on bare motherboard, no IDE, no FDD, no case jumpers [like: turbo, hdd led, etc]. Regarding GeForce - i tried that card on this system, it was not working so i just skipped testing it further.

The only thing that is "out of era" in my testing environment is ATX to AT converter, i use 350W ATX PSU.

Just ordered two ISA graphics card - will try them in few days, however my current [confirmed-working] ISA gfx card do not work on this board.

So i guess the only thing i can do is to order that bios, it will cost ~10$ Should i try or is it dead end?

For $10, you don't have much to loose. Could you upload a single high resolution image of your motherboard? From the images you have provided, there are some areas near the RTC with jumper settings for DMA that are not visible.

I assume you've tried multiple PSUs and reseated the BIOS and PLL chip (UM9515)?

Probably not the case here, but useful to keep in mind, is to check your ATX to AT adapter. The cables tend to dislodge from the back of the 20pin side, especially if you connect/disconnect the adapter all the time. Had this happen countless times, the first ones with me trying to figure out why the motherboard wouldn't boot in the first place, especially when it did work 10 minutes earlier. It's better to keep that thing on a particular PSU and just leave it there, set and forget.

Just like myself and others helping here, I guess You have just skimmed over the config page? Take a closer look and You
might find some things that will help. Your motherboard can flash 5v and 12v eeproms and eproms (if blank only), also
the answer as to why Your cmos isn't being reset and how to reset it is there.

feipoa wrote:

For $10, you don't have much to loose. Could you upload a single high resolution image of your motherboard? From the images you have provided, there are some areas near the RTC with jumper settings for DMA that are not visible.

I assume you've tried multiple PSUs and reseated the BIOS and PLL chip (UM9515)?

Tried all that. Today my Gigabyte GA 486AM/S arrived with DX4 100 CPU, tried that CPU on Biostar MB - no go. Tried my 586 on Gigabyte - that surprised me - also no go. All jumpers are set for AMD DX4 CPU and it doesn't work there - tested MB with other CPU's [all DX4] and it works. Maybe my Am5x86 is broken 😒 still my DX4 CPU should work on Biostar since they work fine on Gigabyte mb. Hence the CPU trail leads nowhere.

So... I found a guy who will write Your firmware file on at29c010a chip for 10$, will see what happens 😀 Hope this chip is compatible with this mb.

Few Biostar mobo pics in hi-res:

Imperious wrote:

Just like myself and others helping here, I guess You have just skimmed over the config page? Take a closer look and You
might find some things that will help. Your motherboard can flash 5v and 12v eeproms and eproms (if blank only), also
the answer as to why Your cmos isn't being reset and how to reset it is there.

Yeah, I know that part of the instructions, tried it all, no luck. JP42 is not soldered to the board, on other side of the MB you can see that the solder dots [where pins should be] are connecter to the non-present battery slot. That part of the manual just doesnt apply to this motherboard [the manual is actually for few biostar mb, not only the 8433UUD model]. Still i tried to short the solder dots - no effect.

opiate wrote:

Yeah, I know that part of the instructions, tried it all, no luck. JP42 is not soldered to the board, on other side of the MB you can see that the solder dots [where pins should be] are connecter to the non-present battery slot. That part of the manual just doesnt apply to this motherboard [the manual is actually for few biostar mb, not only the 8433UUD model]. Still i tried to short the solder dots - no effect.

JP12 pins 3-4 is for shorting the Dallas RTC/Cmos. JP42 is irrelevant, only for board with a CR2032 installed.
You've probably tried that though.

I'll take a look at your jumpers sometime in the next 24-hrs. You can still view the motherboards jumper settings on the Biostar FTP site. Some of them are slightly different than those found elsewhere, but should be the same for the Am5x86-133. I am also working on my updated manual for this board, which I hope to finish in the next few days. It will include instructions on how to upgrade to 1024 K, amongst other things.
ftp://ftp.biostar-usa.com/bios/8400UUD/8400UUDmanual.htm

The jumpers look to be placed correctly to me, however I see that you have your FSB set to 40 MHz. For testing purpose, you will want to set it to 33 MHz, that is, JP15, JP16, JP17 all closed.

While not important at this stage in testing, I see CLKMUL set for 3x. If you are using the Am5x86-133, set JP45 to 1-2, 4-5, which is 4x. Currently, you have it set to 1-2.

Did you order the new BIOS chip? Once it arrives, set JP13 to 1-2. If the system still doesn't light up after changing the BIOS chip, you may need to desolder your RTC.

The DX4-100 chip from the GA486 board may not have worked on your Biostar board because the FSB is set to 40 MHz and 3x, which is 120 MHz.

feipoa wrote:

The jumpers look to be placed correctly to me, however I see that you have your FSB set to 40 MHz. For testing purpose, you wil […]
Show full quote

The jumpers look to be placed correctly to me, however I see that you have your FSB set to 40 MHz. For testing purpose, you will want to set it to 33 MHz, that is, JP15, JP16, JP17 all closed.

While not important at this stage in testing, I see CLKMUL set for 3x. If you are using the Am5x86-133, set JP45 to 1-2, 4-5, which is 4x. Currently, you have it set to 1-2.

Did you order the new BIOS chip? Once it arrives, set JP13 to 1-2. If the system still doesn't light up after changing the BIOS chip, you may need to desolder your RTC.

The DX4-100 chip from the GA486 board may not have worked on your Biostar board because the FSB is set to 40 MHz and 3x, which is 120 MHz.

AAAAAAA!!!!

OMG! IT'S ALIVE! Replacing the bios chip solved my problem [pics attached].

I manage to find one guy in my city who agreed to write your bios file on his own chip, that is why it was so quick 😀

Currently all settings are set for DX4 120, before I will install my 586 i just wan't to make sure i wont break it somehow. So this is my to-do list for installing 586:

- all jumpers [minus cache ones and bios jp13] from this picture (via Imperious):
http://img37.imageshack.us/img37/3355/dscf0057ej.jpg

- all bios options taken from few post up (via feipoa):
PCI IDE IRQ Map To : PCI-AUTO
IDE Primary Master PIO - PIO-4 --------->>> i do plan to use cf card.
DRAM Read/Write = 0WS. -------->>>>>i have 60 ns RAM, plan to use 4X32MB
L2 cache wait states = 2-1-1-1 ---------->>>>>>> i do plan to upgrade to 1MB
Early Cache Write Mode = Enabled
Burst Copy Option = Enabled

Again - BIG THNX for help guys!!! This is going to be great weekend 😁

Glad the BIOS worked out for you.

You have 256 KB of single-banked cache (4 chips + TAG). I am not sure if 2-1-1-1 is stable with a 40 MHz front-side bus. It is better to use 256 KB of double-banked cache (8 chips +TAG), which is stable. Usually, double-banked cache handles faster cache timings than single-banked cache.

feipoa wrote:

Glad the BIOS worked out for you.

You have 256 KB of single-banked cache (4 chips + TAG). I am not sure if 2-1-1-1 is stable with a 40 MHz front-side bus. It is better to use 256 KB of double-banked cache (8 chips +TAG), which is stable. Usually, double-banked cache handles faster cache timings than single-banked cache.

Can't wait to read your updated manual for this mobo, especially that part about 1mb cache, maybe you can share name of the chips, i will order them right now to save time (delivery probably from china).

My 586 is working, currently at 133, dunno if i should go past that at this moment, i don't want to push my luck. Is there a safe margin for this cpu? When the problems started the cpu ran at 160 - maybe that was the problem.

BTW. The Geforce 2 MX400 i own also work! Will contribute to the "Modern graphics on a 486" post after windows/drivers instalation, i don't see my model on the list.

The GeForce 2 MX400 is on the list. See heading: PNY GeForce2 MX400 64MB

I do not beleive the issue is with your Am5x86 at 160 MHz - nearly all Am5x86-133 chips work at 160 MHz. I suspect the issue is with your single-banked cache. Can you pillage 256 K, double-banked from another motherboard? You will need 8 modules with '256' printed on them. You will also need to jumper the board for 256K, double-banked.

512K/1024K double-banked cache on this motherboard will require hardware modification and soldering. You can view some of the work here, Re: The World's Fastest 486 . You will also need some 10 K-ohm SMD resistors and DIP socket offsets as shown. What is lacking in that thread are the instructions, while I am including in version 2 of the motherboard manual.

The SRAM pieces you will want are IS61C1024-10N or IS61C1024-12N. You can also use IS61C1024-15N if you do not plan to ever run the FSB at 66 MHz. If you do not have delicate soldering experience, I do not recommend this mod.

Awesome news!

I've fixed some c64's over the last few years, the fact is that old chips can and do die.
Enjoy Your retro time.

feipoa wrote:

The GeForce 2 MX400 is on the list. See heading: PNY GeForce2 MX400 64MB […]
Show full quote

The GeForce 2 MX400 is on the list. See heading: PNY GeForce2 MX400 64MB

I do not beleive the issue is with your Am5x86 at 160 MHz - nearly all Am5x86-133 chips work at 160 MHz. I suspect the issue is with your single-banked cache. Can you pillage 256 K, double-banked from another motherboard? You will need 8 modules with '256' printed on them. You will also need to jumper the board for 256K, double-banked.

512K/1024K double-banked cache on this motherboard will require hardware modification and soldering. You can view some of the work here, Re: The World's Fastest 486 . You will also need some 10 K-ohm SMD resistors and DIP socket offsets as shown. What is lacking in that thread are the instructions, while I am including in version 2 of the motherboard manual.

The SRAM pieces you will want are IS61C1024-10N or IS61C1024-12N. You can also use IS61C1024-15N if you do not plan to ever run the FSB at 66 MHz. If you do not have delicate soldering experience, I do not recommend this mod.

Just to clarify - to set 160 - on mb version without JP17 - i shoul set JP15 open and JP16 closed?

Now that you mention it - i actually switched cache chips when the problems started. Right now i'm using cache from other mb, found them cheap on ebay.

I noticed that bank1 cache sockets are shorter than bank0. Anyway, i can buy those 256 modules, can you sugest specific marking. Probably someone is selling it on Aliexpress, i know about the failure rate, will order few more just in case i think friend of mine have tester.

For the moment i will stick with no-modding cache option, after i get bored with the board - that will be the time for modding. Soldering doesn't scare me.

My Geforce is from different manufacturer - who knows, maybe the score will be different, will check.

BTW. just found great clip-on cooler with fan for socket 3. This day could not get any better.

JP15 open, JP16 closed. Your JP17 is already closed.

Just grab the '256' cache from another motherboard. Then run the Am5x86 at 160 MHz.

The different sizes of the cache banks, e.g. DIP-32 vs. DIP-28, is the reason the cache mod is needed. It essentially creates eight DIP-32 sockets.

feipoa wrote:

JP15 open, JP16 closed. Your JP17 is already closed.

Just grab the '256' cache from another motherboard. Then run the Am5x86 at 160 MHz.

The different sizes of the cache banks, e.g. DIP-32 vs. DIP-28, is the reason the cache mod is needed. It essentially creates eight DIP-32 sockets.

The only other MB with dip-type cache i have right now is Gigabyte 486 AM/S. Chips will fit the Biostar mobo, but are they compatible?

Here are marks on chips:

- Biostar: UM61512AK-15
- Gigabyte: UM61256FK-15

Pics attached.

I think they won't be compatible -and i base this on absolutely NO knowledge 😀 - , so the only way is to buy new ones, found this:

http://www.datasheets360.com/part/detail/cs18 … anufacturerId=0

Do You think this will work?