VOGONS


First post, by HaveGoals

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First, the issue: When I boot from a DOS floppy, the machine gets to "Starting MS-DOS" and hangs.

The details: I'm in the midst of building a 486/100 machine using a TomatoBoard. This isn't my first rodeo, I've been setting up and supporting computers since the 80s. Everything appears to be connected normally and as far as I can tell, ought to be working. I have two different sets of original DOS disks that work fine on my other machines and another known set I created myself. I have also swapped out three other 3.5" floppy drives. All disks and drives result in the same hang. I have also swapped out the the RAM. Same situation.

Ideas? Thanks!

Reply 1 of 14, by Baoran

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Do floppies work normally if you boot to dos from a hard drive?

I have had 2 motherboards in the past that did the same thing that I get Starting MS-DOS and then it stops, but when I installed a hard drive and booted to dos there I noticed that the floppy drives didn't work properly even when not booting. One motherboard did give just garbled listing when using dir command on a floppy and another motherboard just gave random errors no matter what drive or disk I tried to read. So both motherboards were faulty in a way that only floppy drives were affected. Later I figured what was the problem with one of them when I inspected it and noticed and one of the pins on chipset chip was bent and was touching the pin next to it.

Reply 2 of 14, by HaveGoals

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Baoran wrote on 2020-01-22, 02:30:

Do floppies work normally if you boot to dos from a hard drive?

I have had 2 motherboards in the past that did the same thing that I get Starting MS-DOS and then it stops, but when I installed a hard drive and booted to dos there I noticed that the floppy drives didn't work properly even when not booting. One motherboard did give just garbled listing when using dir command on a floppy and another motherboard just gave random errors no matter what drive or disk I tried to read. So both motherboards were faulty in a way that only floppy drives were affected. Later I figured what was the problem with one of them when I inspected it and noticed and one of the pins on chipset chip was bent and was touching the pin next to it.

Sure enough, the floppy drive works fine if I start it from a hard drive. I will go over the motherboard closely and look for any problems.

Thanks for the help!

Reply 4 of 14, by MAZter

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Incompatible (too large) hard disk drive

Solution: boot from a Western Digital EZ-Drive floppy, install EZ-Drive, everything works fine after that

I had same issue on Compaq LTE5200 laptop

Doom is what you want (c) MAZter

Reply 5 of 14, by Horun

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ychh0 wrote on 2020-05-06, 01:06:

Did you solve this problem? I have the same issue here on my AMD 5x86 160MHz system.

I had a similar issue with my test floppy drive that suddenly quit properly booting, would halt after "Starting MS-DOS". Tried different floppy drives and same problem. Ended up being the cable, which had worked fine the day before.

Your situation could be same or different. Since there is no AMD 5x86 160MHz ....overclocking could cause issues that show up soon or later. Are you sure that the ISA bus is still running at 8mhz and the main bus is still at 33Mhz ? Many times OC will cause the different motherboard chips (including the I/O) to also be clocked at a speed above their rated speed causing floppy, HD, or mouse issues... just a thought !

Hate posting a reply and have to edit it because it made no sense 😁 First computer was an IBM 3270 workstation with CGA monitor. 🤣

Reply 6 of 14, by ychh0

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Horun wrote on 2020-05-06, 02:06:
ychh0 wrote on 2020-05-06, 01:06:

Did you solve this problem? I have the same issue here on my AMD 5x86 160MHz system.

I had a similar issue with my test floppy drive that suddenly quit properly booting, would halt after "Starting MS-DOS". Tried different floppy drives and same problem. Ended up being the cable, which had worked fine the day before.

Your situation could be same or different. Since there is no AMD 5x86 160MHz ....overclocking could cause issues that show up soon or later. Are you sure that the ISA bus is still running at 8mhz and the main bus is still at 33Mhz ? Many times OC will cause the different motherboard chips (including the I/O) to also be clocked at a speed above their rated speed causing floppy, HD, or mouse issues... just a thought !

I tested 25MHz, 33MHz, 40MHz with 1/4 devider for ISA and all couldn’t boot from floppy. I even tested like this ; boot from HDD and format floppy with system transfer option and then rebooted. Result was the same, couldn’t boot from the floppy. I also tried different FDD and cable and no success. Symptom is similar, after showing MS-DOS... then hang.

How did you solve the problem? Simply change cable? Could you explain it more?

Reply 7 of 14, by PC-Engineer

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Do you use L1 cache in Write Backe mode? In the era of later 486 and early pentium the L1 WB was new and often buggy. With the result, that components with DMA and writing into the RAM (bypassing CPU and cache) like Floppys and SCSI controller, caused scrambled RAM content followed by system crashes and scrambled data on the disks.

Try to set L1 to Write Through. If you have L2 in WB mode, it should have nearly zero effect in speed on real 486 CPUs.

1994/1995 - Socket3 - ASUS SV2GX4 / POD 100MHz / 64MB / SCSI - Windows 95

Reply 8 of 14, by ychh0

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PC-Engineer wrote on 2020-05-06, 18:30:

Do you use L1 cache in Write Backe mode? In the era of later 486 and early pentium the L1 WB was new and often buggy. With the result, that components with DMA and writing into the RAM (bypassing CPU and cache) like Floppys and SCSI controller, caused scrambled RAM content followed by system crashes and scrambled data on the disks.

Try to set L1 to Write Through. If you have L2 in WB mode, it should have nearly zero effect in speed on real 486 CPUs.

Yes. I set both L1 and L2 to Write Back mode, also Evergreen 5x86 CPU upgrade module is also set to Write Back mode.
I will test it when I come back home. Thanks

Reply 9 of 14, by Horun

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ychh0 wrote on 2020-05-07, 00:00:
PC-Engineer wrote on 2020-05-06, 18:30:

Do you use L1 cache in Write Backe mode? In the era of later 486 and early pentium the L1 WB was new and often buggy. With the result, that components with DMA and writing into the RAM (bypassing CPU and cache) like Floppys and SCSI controller, caused scrambled RAM content followed by system crashes and scrambled data on the disks.

Try to set L1 to Write Through. If you have L2 in WB mode, it should have nearly zero effect in speed on real 486 CPUs.

Yes. I set both L1 and L2 to Write Back mode, also Evergreen 5x86 CPU upgrade module is also set to Write Back mode.
I will test it when I come back home. Thanks

Good thought PC-Engineer ! Have seen cache issues cause lots of odd problems. Might try turning off both internal and external cache in BIOS and see what happens..

Hate posting a reply and have to edit it because it made no sense 😁 First computer was an IBM 3270 workstation with CGA monitor. 🤣

Reply 11 of 14, by ychh0

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PC-Engineer wrote on 2020-05-06, 18:30:

Do you use L1 cache in Write Backe mode? In the era of later 486 and early pentium the L1 WB was new and often buggy. With the result, that components with DMA and writing into the RAM (bypassing CPU and cache) like Floppys and SCSI controller, caused scrambled RAM content followed by system crashes and scrambled data on the disks.

Try to set L1 to Write Through. If you have L2 in WB mode, it should have nearly zero effect in speed on real 486 CPUs.

I tested all the cases I can think about and the only case that boot succeeded was to turn off L1 cache. Regardless of WT, WB settings of mainboard/CPU upgrade module and various setting regarding L2 cache and DRAM timing, all boot from floppy failed.
I confirmed several times board jumper settings and there are no problems.
I want to find way but couldn’t think more how to do.

Reply 12 of 14, by PC-Engineer

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Maybe the L1 is forced somewhere on the MB to WB. My Asus SV2GX4 has a jumper combination for 486 WB CPUs (AMD SV8B/16B or intel P24D/T and some Cyrix CPUs) The BIOS has a switch to L1 WB/WT with no effect on L1 cache strategy - only the jumper can switch the strategy.
If you use the adapter socket with Am5x86 and voltage regulator, switch the MB jumper to intel iDX/DX2 and the adapter to iDX4.

1994/1995 - Socket3 - ASUS SV2GX4 / POD 100MHz / 64MB / SCSI - Windows 95

Reply 13 of 14, by pentiumspeed

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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?

Cheers,

Great Northern aka Canada.

Reply 14 of 14, by ychh0

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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?

Cheers,

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.