Anyone???

There is a "public" version of the technical manual for this family of chips on the internet.
It shows what each pin on the chip does, so you can try to use it to figure out what the jumpers do.

keeper5511 wrote on 2025-05-19, 19:09:

Anyone???

Can you post a picture of the back of the card too. Usually I'd search for the FCCID value that's on the card which is JR6V743R12 on your card but it doesn't seem to be a common card so there's no pictures or information about it there.

Maybe the back side of the card would give some clues about what the jumpers do.
JP1 being just two pins is probably the IRQ9 jumper which is usually best left open
JP2 from its placement I think it's likely to be a jumper to select which of the memory banks / pads to use. Like if it's got SOJ-40 (256k x 16) memory installed it'd be on the left and if it's got 256k x4 DIP or SoJ chips then it'd be on the right.

JP5 I don't really know

Another thing I can suggest is looking through the vesa local bus card entries on TH99, searching this on google limits the search to cirrus logic VLB cards. Yours isn't in it from what I can tell
"site:https://th99.infania.net/v/ cirrus "vesa local" jp2"

Thank you very much for your reply.

Unfortunately gpu is not working (same bios codes as there is no gpu). I have checked for broken traces, Flash bios and install jumpers on chip. Capacitors have not been checked since they are talantum. GPU's chip seems to warm normally but not picture on the screen. Any ideas to proceed?

Here are some pictures of the back side...

What do you mean you have flashed the BIOS chip? The BIOS in the picture is a type you cannot flash without a UV machine to clear it. Afterwards a sticker should be placed on top to prevent it clearing over time due to sunlight UV.

The jumpers are most likely fine as they are, unless a manual says otherwise. One is IRQ which should not be jumpered. JP5 may be to set a wait-state for systems with a >33Mhz bus clock.

I have flashed another bios chip for in case Bios was corrupted! I have UV light eraser but I have not do anything to the original bios chip.

I am installing this card to one Socket 1 & one Socket 2 motherboard cards. Unfortunately both of them did not recognise the card...

There is no Manual for GPU. I don 't know what other options I have....

Gently probe the chip legs and see if any move, or maybe just drag solder each side
I'd guess the single jumper would probably be IRQ (not needed except in some special cases) one of the others is likely wait states for faster VLB and the 3rd might be additional RAM present.
For a single jumper it obviously has 2 states, on or off, while a 3 pin may have 2 or 3 states... 1-2, 2-3, and off (which may or may not be a valid state)

Chips legs seems ok but 2 red (of 3) talantum capacitors have voltages on both of their legs. May be I must unistall and change them. Does anyome encounter something like this? The first have 5 volt in positive and 2,5 in the negative leg....

keeper5511 wrote on 2025-05-20, 15:23:

I have flashed another bios chip [...]

Is the part number of the new BIOS chip "27C256"? Can also try cleaning the socket or reinserting it a few times to clear oxidisation.

There's a possibility the original BIOS is blank because it does not have the sticker on top, and the new reflashed BIOS is the wrong type.

Another option, the four empty sockets may be required to have buffer ICs in them. Part "74F245PC" or "74F245N".
Many of the similar cards here have those four chips populated: https://www.vgamuseum.info/index.php/componen … logic-cl-gd5426

Hmm. I thought the sockets were for RAM, but with 8x 44256 (256kx4), it already has 2MB, why would they socket required buffer chips though?
It does look like the VLB traces might be going to them though

Thank you all very much for your responses!

The part number of the new chip is M27C512 kai I have verify the data on it. There is no oxidisation on the VLB card, It is in brand in very good condition. I have also check that chip legs are in good (soldered) condition.

So far I am in dead end.... 🙁(((

Actually it has 1Mb ( 2 chips = 256k x 8 ). Usually the other 1mb has sockets, not sure why the SOJ pads are not socketed like most boards, unless those 4 sockets are for ram ?

MikeSG wrote on 2025-05-21, 11:48:

Another option, the four empty sockets may be required to have buffer ICs in them. Part "74F245PC" or "74F245N".
Many of the similar cards here have those four chips populated: https://www.vgamuseum.info/index.php/componen … logic-cl-gd5426

That's it! I am quite disappointed that I didn't notice that myself. It is technically impossible to connect a CL GD-542x family chip to the 486 local bus (or the VLB) without four 74F245 (or similar) buffer chips. You might be able to get away without those buffer chips on a 386 mainboard with on-board video, though. Furthermore, four RAM sockets doesn't make any sense at all, as the bank width of the GD-5426 (or any other GD-542x family except the first revision of the GD-5420) is 32 bits, so this would be just half a bank. While the GD-5426 can operate (at degraded performance) with a single 16-bit bank (512KB), upgrading it to 1.5 MB is not possible. The only possible configurations are: A single 16-bit bank (512K), a single 32-bit bank (1M, like your card) or two 32-bit banks (2M).

Ahh ! guess I should have looked over other cirrus vlb's before posting above. Odd that the 74LS245's were socketed...
here is VLB Ref design schematic from Cirrus 1994Tech Ref...there is an ISA one in that book too

Horun wrote on 2025-05-22, 01:09:

Odd that the 74LS245's were socketed...

Please note that 74LS245 chips are too slow for the VESA local bus. The reference schematic shows 74ALS245 chips which are considerably faster, so are the 74F245 chips. 74ACT245 would work as well.

Hello again! So, this VLB card can not operate without these chips that are missing?

It's highly likely that it can't run without them. They're a common part on Ebay

keeper5511 wrote on 2025-05-22, 09:40:

Hello again! So, this VLB card can not operate without these chips that are missing?

Exactly. Those chips are used to connect the 32 data bits on the VL bus to the 16 data bits on the Cirrus chip. Without these chips, the Cirrus chip is only connected to address lines, but not to data lines.