486 mainboard ID

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486 mainboard ID

Postby irix » Wed Mar 30, 2016 1:38 am

Hi all,

I need to have a 486 board ID'd because it did not run when I got it and I'd like to make it run. I've installed a more standard CPU (board was equipped with a 3V AM486DX4-100) and I'm running through the jumper settings. Most of them are written on the board, but not all of them. If I know what board this is I might be able to find the manual.

It's this board exactly (not my picture), only the numer on the sticker of the BIOS chip differs from mine. It's a Socket 3 mainboard, so it should accept both 3V/5V CPUs.

Image

On the back side of the board it says:

ExpertBoard [C]I2V-0 94V-0 E7163(S) 9452
and there's a logo that looks like the letter D
irix
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Re: 486 mainboard ID

Postby Karlsweldt » Wed Mar 30, 2016 5:21 am

First task is to replace that BIOS battery just by the keyboard port! Starting to grow acidic 'hairs', and that can damage the board's traces. Any signs of green mold or slime can be neutralized with plain vinegar, then some baking soda in solution. And a rinse of plain water. Use dampened bits of rag, no "dousing". Clear nail polish can protect bare traces if needed.
Commonly, the battery is a Varta or other brand.. 3.6 volts nominal. Solder pads are marked as to (+) and (-). If space permits, one of those coin-cell holders could be mounted in place of the battery. But that battery type is still available new.
That battery retains system settings in the CMOS memory, as well as powering the real-time clock. If the clock is not functioning, a good chance of no life signs.
As to the power connections, the two power cables from the PSU must have the black leads together at the center of the sockets! The PSU should be minimal 200 watt, and have a -5 volt signal lead.
Typically there is a 25 MHz and 33 MHz base FSB setting, with multiplier for the CPU. But some CPU models in the 486 class had their own multiplier on the CPU die. A 3.3volt I/O core on the CPU would be fried, if on a 5 volt I/O source. But not the opposite.. may show life signs, maybe not.
Try a default 486/33 CPU on the board, and if life signs, note in the lower left corner of the first screen a string of characters. This is a positive ID of the board and BIOS date.. likely late 1990s. A search of chipset numbers turned up nothing of note.
There are no peripheral ports on board for hard/floppy drives or such.. so a port card with those features would be needed, 16-bit.
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Re: 486 mainboard ID

Postby irix » Wed Mar 30, 2016 5:42 am

Hi,

A already removed the battery, I know them. This is not my picture. I actually found the mainboard type as well, there was a sticker beneath the last VESA-port:

EXP4045

http://stason.org/TULARC/pc/motherboard ... P4045.html
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Re: 486 mainboard ID

Postby evasive » Wed Mar 30, 2016 6:31 am

DataExpert. Manual:
http://www.elhvb.com/mobokive/Archive/D ... index.html

donations welcome (main page)
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Re: 486 mainboard ID

Postby irix » Wed Mar 30, 2016 9:16 am

Thanks. Unfortunatly the motherboard is still not running. I've set it to the correct specs, I've got tested working memory, a working ISA VGA card (tested a VLB and non-VLB one).
No speaker beeps, no POST, but the LEDs on the keyboard are full on all the time.
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Re: 486 mainboard ID

Postby Karlsweldt » Wed Mar 30, 2016 3:55 pm

Lacking a POST diagnostics card, the keyboard lights are a basic diagnostic tool. Should flash on and off when powering up, then about 5 seconds later, another flash or two, as the POST regimen tests all features. If no second flash sequence, there was a critical error found, and the POST process halted. Or the CPU is not functioning.
You need more than just a video card for those older non-ported boards. An I/O port card is required for a good POST check.
The CPU will get a bit warm, even if not active (resistance loading). A lot warmer when active (dynamic loading).
Memory for that board, if 72-pin SIMMS, should be at least 80ns.. noted by the last character(s) on the chips for the ID. 60ns would be better. And non-ECC.
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Re: 486 mainboard ID

Postby evasive » Wed Mar 30, 2016 9:47 pm

Do you have an other power supply to try and test with? Put no memory VGA whatever in there. Also do not connect the keyboard just yet when testing, keep this thing as bare as possible, we want beeps first to show that it can actually detect something is wrong. Once you got it to beep for no memory put a 4MB stick of memory. If it then beeps for no video put in the VGA card (I assume that is tested known good in another board).
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Re: 486 mainboard ID

Postby irix » Thu Mar 31, 2016 1:09 am

Karlsweldt wrote:Lacking a POST diagnostics card, the keyboard lights are a basic diagnostic tool. Should flash on and off when powering up, then about 5 seconds later, another flash or two, as the POST regimen tests all features. If no second flash sequence, there was a critical error found, and the POST process halted. Or the CPU is not functioning.
You need more than just a video card for those older non-ported boards. An I/O port card is required for a good POST check.
The CPU will get a bit warm, even if not active (resistance loading). A lot warmer when active (dynamic loading).
Memory for that board, if 72-pin SIMMS, should be at least 80ns.. noted by the last character(s) on the chips for the ID. 60ns would be better. And non-ECC.


Ofcourse the I/O card is connected (and tested on another board) as well. Memory is tested as well, tried 60ns and 70ns.
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Re: 486 mainboard ID

Postby Twisty » Thu Mar 31, 2016 10:08 pm

I suspect I'm teaching you to suck eggs here but just thought I'd point out the mem DIMMS need to be installed in pairs, and generally in alternating slots.
I'd double/triple check the PSU and all the jumper settings, I'd carefully use a volt meter to check the CPU is getting the correct voltage.
Usually next on the list is checking all the caps, but I see your board has tantalum caps which I find never to be a problem.
Then I'm stumped, maybe check the BIOS chip has a valid ROM on it, long shot and a pain to check but if it's been left somewhere where the sun then the BIOS could've been corrupted.
I have now left the Building :tongue8:
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