OldComp.cz

So, you mean it is not a cause of memory issues? If so, I don't understand where I have to look for problems on board.
Can you check if the same levels on your device's memory? Did you used the same ic series for ic6 and ic7?

I used the BOM as on Alexandru's page and bought everything what was possible from Mouser. I do not like Chinese shops, unless it is absolutely necessary, because of poor quality and/or fakes.

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I removed keyboard controller, boot process slows down, and it is possible to view most of postcodes sequentially. Looks 23 - latest code before reboot.

I just had changed bios on mrbios, got from Martin. No 74f08 soldered yet.

Congrats, it looks almost working

I measured output of my 74ACT373 (IC6 pin 2) and 74F244 (IC7 pin 3) and it is as expected. About 3.5V logic HIGH from 74F244 and about 4.8V logic HIGH from 74ACT373.

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Got and soldered 74f08.
Looks no dma issues with my snark barker sb 1.0 replica.
Ps/2 mouse also workable
Upd: do you know keys combination to enter bios settings? F1, F2 or del did not had worked.

PS/2 mouse works with MR BIOS, but not AMI BIOS (at least the 2 that I have).
I tested Sound Blaster AWE64, DMA and all other test pass OK, but sometimes the sound is corrupted and I got suspicious, that also harddrive data got corrupted for time to time, when I have Sound Blaster in system.
MR BIOS has setup key <ESC>

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Latest board state. FPU socket not soldered yet, used 74abt244 instead 74f244. CPU was simply overclocked 25->40 MHz without any issues.

Looks ps/2 issues related with bios support only. Regarding DMA, looks it is need to check the systems stability. Cf data in safety, due I used ISA CF board, without dma support.

I use stadnard IDE (0x1F0) controller, as it is more than twice faster as XT CF IDE. It does not use DMA either. I can use it with standard BIOS or XT IDE Universal BIOS, both work OK. I am not sure about the data corruption, but it happened twice and since I removed the Sound Blaster from system it is rock solid stable.

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Did you tried to increase a waitstates on bios dma tab?

Na oldcomp FTP2 jsem dal do \PC\bios\OPTI různé posbírané BIOSy z desek 386 co měli OPTI chipset. Zatím nevyzkoušené.

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Martin, did you turned on internal cache of your 486 cpu?
I tried to install one, but turning on internal cache nonalternatively hungs the system.

When the processor (internal cache) and the external cache have the same clock frequency (40MHz), the difference in performance is insignificant.

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This apply only with 0 WS. If any wait state to the external cache is inserted, the performance of external cache will suffer significantly against internal cache. If you even have only RAM with 0 WS, you technically don't need cache at all.

In real world however, internal cache is always fastest option available. If cache runs synchronous with 0 WS than internal cache is not so important except the fact we have more fast RAM available with L1+cache on board.

486DLC without internal L1 cache enabled is "better performing 386," but with L1 cache enabled it is much better performer, especially in demanding games like DOOM/benchmarks. The difference is like +18% performance speedup for the same PC. https://www.philscomputerlab.com/cyrix-486dlc.html Not saying there was Ti486SXL later version with full 8 kB L1 cache as "normal" 486 which had even bigger speed-up:-).