pentiumspeed wrote on 2020-05-07, 23:04:
Could be the bad CPU or the motherboard is failing? May have to replace the cache chips also. If you got cache chips from china, that could be one of these issues of quality.
Use different settings that is for WT CPU for your CPU otherwise get another CPU with WT instead?
What I did are as follows
- Mainboard recap (all the capacitors)
- Cache ram change ; W24257AK-15 256kB/IS61C1024-10 512kB
- Ram change ; EDO 64MB, FPM 128MB
- BIOS setting ; WB, WT, various settings regarding DRAM timing and L1/L2 cache settings
- CPU upgrade moule ; Evergreen Rev to 486, PNY Quickchip 133 (both are AMD 5x86 CPU upgrade modules)
- CPU upgrade module setting ; WB/WT for Evergreen, Pass Through/Write Through for PNY
- Mainboard jumper settings ; 3 types (http://th2chips.freeservers.com/syl8884/ ; I have ST1A REV.B board) and WB/WT (guess)
All the settings fail to boot from floppy. But it can boot from IDE HDD or SCSI HDD if I set L2 cache timing more than 2-2-2-2 and after boot it can read/write floppy with no problem.
I guess jumper 22 is related with WB/WT setting and setup in the BIOS or CPU upgrade module actually do not change setting of WB/WT. (it's just guess. Only when mainboard jumper 22 set to 2-3 speedsys benchmark score increased about 4~5% compared with all the other cases. I guess this is due to L1 WB setting)
From the above results, I guess floppy does not boot regardless of WB/WT setting. Only when L1 cache off it can boot.
Currently I cannot but to use this setting normally and only when I should boot from floppy, I should turn off the L1 cache.
It's very strange.... I wonder anyone who have experienced this kind of unusual case.