VLB build problems, again (ASUS VL/I-SV2GX4) \ VOGONS

VLB build problems, again (ASUS VL/I-SV2GX4)

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First post, by nemail

Posted on 2016-09-20, 21:10

nemail Offline

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it's me again, trying to make a DX4-100 VLB build and failing hard.
This time it is an ASUS VL/I-SV2GX4 and an Intel 486 DX4 100 MHz which I'm trying to build together.
However, when I start the system, it POSTs and when it tries to boot from floppy or hdd, it stops right after "Starting MS-DOS", regardless of the boot source.

I've tried various VLB I/O cards and VLB VGA cards, as well as several hard disks below 8GB (even one with 200MB) and also several memory sticks.

What I came across however, was that sometimes when POSTing, the BIOS would say that the floppy drive failed. Also, sometimes I get the beep code for faulty video memory. Sometimes I have to wiggle around with the vga card a bit, sometimes a reset is enough and sometimes I had to reseat the vga card to get it POSTing again.

I think this is more a bad contact on the ISA or VLB bus than a faulty card.

What surprises me however, is that regardless of what I try, the main error always is the same and nothing I did, changed anything regarding this. The system just stops after writing "Starting MS-DOS".

any ideas to start searching? try a non vlb i/o card? reflash (newer) BIOS? try another CPU?

As this mobo does have a coin cell battery, there is absolutely no corrosion. also, the motherboard isn't bent.

thanks!

Reply 1 of 12, by vetz

Posted on 2016-09-20, 21:15

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This sounds like a cache config problem, check your jumper settings. It could also be that the CPU settings/j umpers are incorrect, and is set for writeback mode, while the DX 100 normally only supports writethrough.

Full manual for this board have been uploaded by Artex here on Vogons.

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Reply 2 of 12, by nemail

Posted on 2016-09-20, 21:44

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vetz wrote:
This sounds like a cache config problem, check your jumper settings. It could also be that the CPU settings/j umpers are incorrect, and is set for writeback mode, while the DX 100 normally only supports writethrough.

Full manual for this board have been uploaded by Artex here on Vogons.

I checked the whole manual and all jumpers before powering on the board for the first time.
The board has 8 W24257AK-15 as cache and one W24257AK-15 as TAG ram.
the jumpers are configured for 8 chips and 256k so i guess thats correct.
maybe i should try to reseat the cache and tag?

Reply 3 of 12, by firage

Posted on 2016-09-21, 04:50

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Try if it boots with external cache disabled in BIOS first.

CPU jumpers are kind of a journey with this board, esp. if you want write-back enabled. Check and re-check jumpers on the I/O card too.

My big-red-switch 486

Reply 4 of 12, by vetz

Posted on 2016-09-21, 05:59

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Please check that L1 cache is set to WT both in BIOS and on CPU jumpers.

Only have it set to WB if your CPU is a &EW model (Intel i486DX4-100 &EW)

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Reply 5 of 12, by nemail

Posted on 2016-09-21, 06:11

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will look into that, today evening (CEST, UTC+01:00 +DST). thanks!

Reply 6 of 12, by nemail

Posted on 2016-09-21, 15:59

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Got it!!!
Thanks all for the help!

Actually, this processor IS the &EW variant and I did jumper the board for the &E type CPU.
As soon as I disabled the internal L1 cache in BIOS, the system started booting so I kept looking into the jumper settings and finally set it to

JP16 1-2, 5-6 short for WT (didn't short 1-2 and 5-6 as I'm wanting WB)
JP17 1-2, 5-6 short
JP18 1-2 short
JP19 1-2, 3-4, 5-6 short
JP20 All Open for 3x clk
JP21 2-3 short for WT (didn't short 2-3 as I'm wanting WB)
JP22 1-2, 4-5 short

now everything seems to work, I will continue to report here and maybe start a new thread, introducing this nice little build to all of you.

Thanks again!!

Reply 7 of 12, by nemail

Posted on 2016-09-21, 21:48

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Update: Speedsys shows no L2 cache, although, when booting it shows 256KB in the summary.

Internal and External Caches are enabled in BIOS and jumper cache config is also double-checked.

What could be the problem?
I have nine pieces of W24257AK-15 as cache on the board.

thanks!

Reply 8 of 12, by TheMobRules

Posted on 2016-09-21, 22:10

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nemail wrote:
Update: Speedsys shows no L2 cache, although, when booting it shows 256KB in the summary. […]
Show full quote
Update: Speedsys shows no L2 cache, although, when booting it shows 256KB in the summary.

Internal and External Caches are enabled in BIOS and jumper cache config is also double-checked.

What could be the problem?
I have nine pieces of W24257AK-15 as cache on the board.

thanks!

Maybe you can try setting tighter cache timings in the BIOS? I have a 486 motherboard that does not get its cache detected by SpeedSys or CacheChk with the default settings but if I set the timings manually to a less conservative value it works fine.

Reply 9 of 12, by nemail

Posted on 2016-09-22, 21:49

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ok now, nothing i tried helped. I'm pushing the board to its limits, regarding timings and speed, getting decent results even without L2 cache. With L2 however, performance would be even better, I guess.

i tried all bios settings, even shorted JP21 3-4, which gave me an additional performance boost (maybe L1 WB got finally enabled completely).
during POST, the 256KB cache are shown as present.
Speedsys results don't vary if I disable L2 cache in the BIOS.
I have BIOS version 0401.

i have
JP16 1-2, 5-6 open
JP17 1-2, 5-6 short
JP18 1-2 short
JP19 1-2, 3-4, 5-6 short
JP20 All Open for 3x clk
JP21 3-4 short
JP22 1-2, 4-5 short

JP5, JP6 1-2 short

according to the pdf manual, the htm files and text file infos in https://www.vogonsdrivers.com/files/ASUS_486S … _and_manual.zip

i did read this: https://groups.google.com/forum/#!topic/comp. … ips/O1uZAsY8i6w
and this: How to set Asus VL/I-486SV2GX4 (SiS471) into L2:Write-through mode?, however I didn't understand why one would like to have L2 cache in WT mode, instead of WB mode...
and this: https://ancientelectronics.wordpress.com/tag/fake-cache/

i did try 2x16MB sticks and various 1x16MB sticks, all FPM i believe, as EDO wouldn't even POST in this board, AFAIK. Also, a few months earlier I looked up the IC names of my sticks and then wrote FPM on FPM modules to be able to distinguish between EDO and FPM.

i even reseated all the cache chips.
do I need to update my BIOS?
would have to hot flash it in another board then and first find a suitable EEPROM... 😵

@artex: you seem to have the exact same setup as I do (regarding CPU, cache and board). see: Artex's Build of the Week: Intel DX4 100 Write Back Enhanced - the Classic!
would you share your jumper settings with me? I'd be extremely grateful...

these are my results: