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Overclocking DX4 100MHZ to 120?

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Reply 20 of 29, by Charleston

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jakethompson1 wrote on 2021-10-27, 03:45:
Charleston wrote on 2021-10-27, 03:40:
jakethompson1 wrote on 2021-10-27, 03:32:

And when you are using the Am5x86, you are using the P24D (WB) jumper settings?

Yeah, I'm just redoing everything through the manual. Amd doesn't get past wait screen when set properly, regardless of speed.

No difference with L2 (external cache) off? With DRAM wait states set to the highest? With L1 (internal cache) off? WAIT... is usually when the BIOS switches from the pessimistic settings burned into the BIOS ROM, to whatever you've configured in the CMOS setup.
If L2 off helps, something is too aggressive for your bus speed or cache chips. Likewise with DRAM wait states and your SIMMs. L1 off helping would indicate a problem with the L1 write-back stuff although usually it would get past that point and hang when booting from a floppy.

I'll try turning on a wait state and see if that makes a difference... This is really kind of a strange thing. It just doesn't like anything more than 100mhz but apparently it hates amd now too.

Reply 21 of 29, by Charleston

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jakethompson1 wrote on 2021-10-27, 03:47:
Charleston wrote on 2021-10-27, 03:40:

Edit: so it seems when set to amd settings after leaving it on long enough it's actually getting a c drive error?

Interesting! since it's established you are using an ISA IDE interface and not VLB, CPU/bus speed shouldn't be a factor in that. Everything IDE is hooked up correctly?

Yep, everything is hooked properly. When I go back to dx4 jumper config and throw in the dx4100 it boots perfect. I have my vesa bus set to 33 too but it doesn't make much a difference.

BTW cache is 15ns if that makes a difference in stability.

Reply 22 of 29, by jakethompson1

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Charleston wrote on 2021-10-27, 04:30:
jakethompson1 wrote on 2021-10-27, 03:47:
Charleston wrote on 2021-10-27, 03:40:

Edit: so it seems when set to amd settings after leaving it on long enough it's actually getting a c drive error?

Interesting! since it's established you are using an ISA IDE interface and not VLB, CPU/bus speed shouldn't be a factor in that. Everything IDE is hooked up correctly?

Yep, everything is hooked properly. When I go back to dx4 jumper config and throw in the dx4100 it boots perfect. I have my vesa bus set to 33 too but it doesn't make much a difference.

BTW cache is 15ns if that makes a difference in stability.

If it's the same DX4 as on the other thread, it is an &E (write-through only) model, which means if something is wrong with L1 WB on your board, it won't matter with the DX4.
The 5x86 is definitely WB-capable, so that's a difference between them. You could try P24D WT to force it into write-through mode and see if that helps. Or, disabling internal cache as a test only.

Reply 24 of 29, by jakethompson1

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Charleston wrote on 2021-10-27, 04:57:

What would cause the write back of this board to be bad? I wouldn't be so bent up about it if parts weren't so dang expensive nowadays.

Well here is what I ran into: EFA 4DMS HL3G VI - INV/HITM# jumpers for WB CPU not working
However, mine was almost completely working except for floppy access, which uses ISA DMA and therefore requires all the L1 WB stuff to be working completely.
If you can narrow it down to an L1 WB issue--either by disabling L1 in BIOS or re-jumpering as WT--then you may be able to add some jumper wires to the board and get it working.

Reply 29 of 29, by Charleston

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So I'm just going to get another bios eeprom to program that would be compatible, my slot has 32 pins but the bios currently used has 28 so whatever.

Worst case I stick with what I have and keep working on getting the dx4-100 to overclock to a 40mhz bus as that should give slightly more umph over the amd 133 at 120mhz. My biggest issue is that when turbo is set the whole system locks up which bothers me but whatever. Thanks for the help.