Fake cache board, reboot loop after adding real cache

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Fake cache board, reboot loop after adding real cache

Postby quicknick » 2018-4-25 @ 23:46

Tried today to add some real cache instead of the horrible soft-plastic blocks pretending to be cache chips on a (Azza?) 4SGS-3VL board. First i removed the hard-wired "jumpers" and soldered some headers instead, then i filled the first bank with four 512kbit chips and a 256kbit as TAG RAM, set the jumpers accordingly but the board gets stuck in a reboot loop, it restarts after the memory count, right when the "Energy Star" logo fades away.

If i play around with cache jumpers, with some combinations it goes a bit further and reports 32KB cache size and gets stuck with a incompletely drawn system configuration table.

What could be wrong? Maybe the board/faked bios expects both banks filled with 256kbit chips (as the plastic one were marked) and won't work with any other size or combination of chips?
Or, as you can see in the photos, this has something to do with the two missing 74F244 chips? There are few photos of this board on the net, and most show it without these chips, but there is one (with cache that at least looks real) that has the 74F244 chips installed, so maybe i should try to source and install them?

4SGS-3VL before.jpg

4SGS-3VL after.jpg


Disregard the red jumper, i only soldered a header there for testing, and will remove it if/when i'll solder the F244 chip. Playing around with this jumper doesn't seem to change anything.
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Re: Fake cache board, reboot loop after adding real cache

Postby keropi » 2018-4-26 @ 05:24

Well judging from the visible traces that seem to connect the F244s to the cache ICs and that other pic you mention I really think you need to populate those two 244s as well. Put them in sockets just in case...
What about the other nearby passives? Any clue on that other photo?
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Re: Fake cache board, reboot loop after adding real cache

Postby Tiido » 2018-4-26 @ 05:52

Pentium's databus is 64bits wide so you need 8 cache chips to fill it. 4 is not gonna cut it.
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Re: Fake cache board, reboot loop after adding real cache

Postby quicknick » 2018-4-26 @ 08:50

@keropi - thanks, i'll try that. The pic from the net is below, the passives seem the same - mostly unpopulated :)

@Tiido - forgot to mention, it's a Socket 3 board, so it should work with 4 chips.

aaa05s-l1600 (3).jpg
Last edited by quicknick on 2018-4-26 @ 09:22, edited 1 time in total.
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Re: Fake cache board, reboot loop after adding real cache

Postby Tiido » 2018-4-26 @ 08:52

Whoops, my bad haha.

In that case there might be some jumper that needs change, my 486 has a jumper that allows to choose between single (4 chips) or dual bank (8 chips) operation.
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Re: Fake cache board, reboot loop after adding real cache

Postby quicknick » 2018-4-27 @ 22:39

I am happy to report that the problem is gone after fitting the two chips, and that 74HCT244 works perfectly instead of 74F244 which i couldn't find anywhere. Thanks again for your advice, keropi!

4SGS-3VL working.jpg

4SGS-3VL speedsys.jpg
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Re: Fake cache board, reboot loop after adding real cache

Postby oeuvre » 2018-4-28 @ 13:55

Glad to hear! Also sweet avatar.
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