Need jumper manual for ASI MB-4DPG (486DX4 PCI)

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Postby evasive » Thu Jul 19, 2012 12:30 am

@8bitbubsy: do you have a 5V CPU to test with? DX33 if possible? That way if you set the bus speed to 33 it will at least boot and we can work from there.
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Postby 8bitbubsy » Thu Jul 19, 2012 12:32 am

I have a 486DX66, it doesn't POST with it either. Also I have no clue where to set the bus speed, I've tried many different combinations of the jumpers near the CPU, no nothing. Not even a beep from the internal speaker (I have put the jumper on the speaker header so it's enabled). Tried different combination of SIMM modules, in different orders and so on.
I don't get a sync signal from the internal video card, I even tried a PCI video card, no sync at all.

Ok here's the full story so you won't get confused:
I found this machine outside of an electronics store, they receive old electronics that goes to the dumpster. I took it home and fired it up, but the PSU was dead. I have yet not found out what's wrong, the fuse is OK, start-up resistors are OK etc (this is another topic).
Then I tried a bog-standard 486 AT PSU, and it booted up. It had a DX4 100 installed. I had another 486 back then so I didn't care more for this machine because any AT PSU would not fit inside the small chassis. Some years later I eventually started to take jumpers from the mobo because I needed them in another system, that's how I messed up the mobo in the first place...

Well here I am, trying to revive it from its death. I really want a nice 486 system for nostalgic reasons, also it's one FAST 486 system or what not.

Oh, not to mention that it's one rare piece of a 486 motherboard, so I want to contribute whatever I can find on it. It's kind of exciting!
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Postby evasive » Thu Jul 19, 2012 1:04 am

I see... In that case I think you will have to go one step deeper and find where the jumper traces are going and match the pins on the CPU with its function and make an educated guess on the function of the jumper block. Another option would be to compare other 486 boards made by ASI, there is a remote chance they have copied the jumper settings layout between board, although that's rare in that era, as board space was scarce...
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Postby 8bitbubsy » Thu Jul 19, 2012 1:05 am

I have already checked all the other ASI boards online, the jumper configuration doesn't match the least.
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Postby Karlsweldt » Thu Jul 19, 2012 9:11 am

Some of those jumpers configure the cache type and amount, others the core and I/O voltage, bus speed and multiplier.. as well if the CPU is an "SX" or "DX" type. The suggestion by evasive to use a plain DX33 type may show some life signs.
There are hundreds of old 486 mobo models listed on eBay.. but nothing close to this one in design. That single slot is the crossover ISA/VESA design. Dell, AST and other brands had similar boards, but not the same layout as yours.
Without a pinout diagram, it will be frustrating to "trace" the circuits.. so here is a link for the 486 CPU pinout.. with functions! http://pclinks.xtreemhost.com/486pin.htm
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Postby 8bitbubsy » Fri Jul 20, 2012 4:15 am

Karlsweldt wrote:Some of those jumpers configure the cache type and amount, others the core and I/O voltage, bus speed and multiplier.. as well if the CPU is an "SX" or "DX" type. The suggestion by evasive to use a plain DX33 type may show some life signs.
There are hundreds of old 486 mobo models listed on eBay.. but nothing close to this one in design. That single slot is the crossover ISA/VESA design. Dell, AST and other brands had similar boards, but not the same layout as yours.
Without a pinout diagram, it will be frustrating to "trace" the circuits.. so here is a link for the 486 CPU pinout.. with functions! http://pclinks.xtreemhost.com/486pin.htm

I know that, also a DX2-66 runs on 33MHz and it doubles the clock internally. It would be the same, I said that I tested with a DX2 and it showed no life. I also know that there's jumpers for cache size (64kB .. 256kB usually), bus speed, multiplier and so on.. I wrote in another post that I tested many combination with no luck. :roll:

Newer Socket 3 slots supposedly have auto-sense 5v/3.3v, so just measuring the VCC pins is nonsense, a different result occurs when you insert an actual CPU in the slot. I could try to short the sensing pins to force either 5v or 3.3v, but that would be meaningless, wouldn't it..
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Postby Karlsweldt » Fri Jul 20, 2012 4:48 am

No offense meant in those suggestions as to other routes to explore. While you may have good knowledge of computer design and workings, others who view this post may gain some knowledge.
In a situation like this, I rely on a POST diagnostics card ( eBay link ) to display a code as to the probable fault. But in your case, you would need an ISA-type model, plus the riser card for that motherboard.
And from past experience with those designs, some require the riser card to be installed before life-signs are present! That particular motherboard may only have ISA card features, but possible it also has PCI card features. The first PCI 1.0 version device card slot appeared in 1992. Design of that version was started two years prior. Since some chipsets on your board are dated to 1995, very possible.
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Postby 8bitbubsy » Fri Jul 20, 2012 4:50 am

Yeah, I always have the slot riser in when testing the system. It has 2x PCI and 2x ISA, also the ones you linked to on eBay is for both PCI and ISA (you can turn them around, look at the picture).

Anyhow, thanks for the suggestion, I'll definitely buy one of those. If it doesn't help me here, it might help me another day on another computer. :)
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Postby Twisty » Fri Jul 20, 2012 1:35 pm

8bitbubsy wrote:Newer Socket 3 slots supposedly have auto-sense 5v/3.3v, so just measuring the VCC pins is nonsense, a different result occurs when you insert an actual CPU in the slot. I could try to short the sensing pins to force either 5v or 3.3v, but that would be meaningless, wouldn't it..


Didn't realise that some 486 boards had auto-sense. I guess what I should have said is have you checked that the CPU is getting 3.3v.
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Postby Karlsweldt » Sat Jul 21, 2012 5:09 am

Auto-sense only in the means of showing the CPU speed and type. The 3.3 volt only CPU types had an extra pin, so it could not be inserted into the 5 volt only socket. The DX2-50 and DX2-66 5 volt class had internal regulators and clock doublers. The Intel "Overdrive" types were 3.3 volt class.. with the extra keying pin. For 'upgrade' CPU types, you had to set jumpers on the board.. or fry the CPU. The Socket 5 and Socket 7 types also did not have auto-sense as to setting the core/IO voltage levels. That came to be with the Socket 370 series and Slot 1/Slot A series.
Here is another link to processor socket types.. with pinouts.
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