It turns out that booting from MS-DOS I can't run most of .exe files from a floppy, but booting from a bootdisk I can run/copy some or most of them 🤔

Is your CPU a SV8B or a (N)V8T ?
What BIOS do you use? AMI or Award?

Disruptor wrote on 2022-11-26, 18:14:

Is your CPU a SV8B or a (N)V8T ?
What BIOS do you use? AMI or Award?

I think it's a SV8B, because it's and "AM486DX4-S"
Regarding the BIOS it's an Award BIOS on a UV-EPROM chip.

AndalusianRG wrote on 2022-11-26, 18:39:

Disruptor wrote on 2022-11-26, 18:14:

Is your CPU a SV8B or a (N)V8T ?
What BIOS do you use? AMI or Award?

I think it's a SV8B, because it's and "AM486DX4-S"
Regarding the BIOS it's an Award BIOS on a UV-EPROM chip.

If the BIOS reports the processor as AM486DX4-S, it is most likely an SV8B. The "-S" indicates SMM (system management mode) support. I never saw the V8T, but if I understand the story correctly, the V8T also includes an SMM using Intel's SMM microcode. As IP lawyers decided that AMD doesn't have a license for that, they produced the non-SMM NV8T with Intel's SMM microcode removed.

The BIOS detects the SV8T processor using the CPU identification (using CPUID or the register contents after reset). The BIOS of an advanced 486 board (like your Biostar MB8433-UUD) then assumes that the processor is jumpered according to the manual. The symptoms you are describing can arise if the processor is jumpered as non-enhanced DX4, but the BIOS configures the chipset for a correctly jumpered enhanced DX4. So please double-check the CPU jumpering. Thost late 486 boards contain a lot of jumpers that need to be set correctly for the CPU to work correctly.

It's funny that your BIOS tries to "update ESCD" when it is stored in an UV EPROM. The ESCD ("extended system configuration data") is a dedicated area in a flash BIOS chip that contains a table of installed hardware. This data is dynamically generated during the POST and written using the usual flashing process. I wonder why anyone ever programmed a UV erasable EPROM chip with code that tries to do ESCD updates. The jumper manual indicates that JP13 should not be installed when an UV EPROM is installed, but I don't know whether the BIOS is able to read back the setting of this jumper. So either your EPROM contains a BIOS version that's not meant to be used in EPROMs, or the jumpering is wrong.

mkarcher wrote on 2022-11-26, 19:29:

If the BIOS reports the processor as AM486DX4-S, it is most likely an SV8B. The "-S" indicates SMM (system management mode) supp […]
Show full quote

AndalusianRG wrote on 2022-11-26, 18:39:

Disruptor wrote on 2022-11-26, 18:14:

Is your CPU a SV8B or a (N)V8T ?
What BIOS do you use? AMI or Award?

I think it's a SV8B, because it's and "AM486DX4-S"
Regarding the BIOS it's an Award BIOS on a UV-EPROM chip.

If the BIOS reports the processor as AM486DX4-S, it is most likely an SV8B. The "-S" indicates SMM (system management mode) support. I never saw the V8T, but if I understand the story correctly, the V8T also includes an SMM using Intel's SMM microcode. As IP lawyers decided that AMD doesn't have a license for that, they produced the non-SMM NV8T with Intel's SMM microcode removed.

The BIOS detects the SV8T processor using the CPU identification (using CPUID or the register contents after reset). The BIOS of an advanced 486 board (like your Biostar MB8433-UUD) then assumes that the processor is jumpered according to the manual. The symptoms you are describing can arise if the processor is jumpered as non-enhanced DX4, but the BIOS configures the chipset for a correctly jumpered enhanced DX4. So please double-check the CPU jumpering. Thost late 486 boards contain a lot of jumpers that need to be set correctly for the CPU to work correctly.

It's funny that your BIOS tries to "update ESCD" when it is stored in an UV EPROM. The ESCD ("extended system configuration data") is a dedicated area in a flash BIOS chip that contains a table of installed hardware. This data is dynamically generated during the POST and written using the usual flashing process. I wonder why anyone ever programmed a UV erasable EPROM chip with code that tries to do ESCD updates. The jumper manual indicates that JP13 should not be installed when an UV EPROM is installed, but I don't know whether the BIOS is able to read back the setting of this jumper. So either your EPROM contains a BIOS version that's not meant to be used in EPROMs, or the jumpering is wrong.

The chip that contain the bios is a Texas Instrument TMs jl27c010a-15.

mkarcher wrote on 2022-11-26, 19:29:

If the BIOS reports the processor as AM486DX4-S, it is most likely an SV8B. The "-S" indicates SMM (system management mode) supp […]
Show full quote

AndalusianRG wrote on 2022-11-26, 18:39:

Disruptor wrote on 2022-11-26, 18:14:

Is your CPU a SV8B or a (N)V8T ?
What BIOS do you use? AMI or Award?

I think it's a SV8B, because it's and "AM486DX4-S"
Regarding the BIOS it's an Award BIOS on a UV-EPROM chip.

If the BIOS reports the processor as AM486DX4-S, it is most likely an SV8B. The "-S" indicates SMM (system management mode) support. I never saw the V8T, but if I understand the story correctly, the V8T also includes an SMM using Intel's SMM microcode. As IP lawyers decided that AMD doesn't have a license for that, they produced the non-SMM NV8T with Intel's SMM microcode removed.

The BIOS detects the SV8T processor using the CPU identification (using CPUID or the register contents after reset). The BIOS of an advanced 486 board (like your Biostar MB8433-UUD) then assumes that the processor is jumpered according to the manual. The symptoms you are describing can arise if the processor is jumpered as non-enhanced DX4, but the BIOS configures the chipset for a correctly jumpered enhanced DX4. So please double-check the CPU jumpering. Thost late 486 boards contain a lot of jumpers that need to be set correctly for the CPU to work correctly.

It's funny that your BIOS tries to "update ESCD" when it is stored in an UV EPROM. The ESCD ("extended system configuration data") is a dedicated area in a flash BIOS chip that contains a table of installed hardware. This data is dynamically generated during the POST and written using the usual flashing process. I wonder why anyone ever programmed a UV erasable EPROM chip with code that tries to do ESCD updates. The jumper manual indicates that JP13 should not be installed when an UV EPROM is installed, but I don't know whether the BIOS is able to read back the setting of this jumper. So either your EPROM contains a BIOS version that's not meant to be used in EPROMs, or the jumpering is wrong.

I've bought a Winbond chip just in case I'd need to hotswap if by replacing the RTC the problems are still there. Thank you very much!

mkarcher wrote on 2022-11-26, 19:29:

If the BIOS reports the processor as AM486DX4-S, it is most likely an SV8B. The "-S" indicates SMM (system management mode) supp […]
Show full quote

AndalusianRG wrote on 2022-11-26, 18:39:

Disruptor wrote on 2022-11-26, 18:14:

Is your CPU a SV8B or a (N)V8T ?
What BIOS do you use? AMI or Award?

I think it's a SV8B, because it's and "AM486DX4-S"
Regarding the BIOS it's an Award BIOS on a UV-EPROM chip.

If the BIOS reports the processor as AM486DX4-S, it is most likely an SV8B. The "-S" indicates SMM (system management mode) support. I never saw the V8T, but if I understand the story correctly, the V8T also includes an SMM using Intel's SMM microcode. As IP lawyers decided that AMD doesn't have a license for that, they produced the non-SMM NV8T with Intel's SMM microcode removed.

The BIOS detects the SV8T processor using the CPU identification (using CPUID or the register contents after reset). The BIOS of an advanced 486 board (like your Biostar MB8433-UUD) then assumes that the processor is jumpered according to the manual. The symptoms you are describing can arise if the processor is jumpered as non-enhanced DX4, but the BIOS configures the chipset for a correctly jumpered enhanced DX4. So please double-check the CPU jumpering. Thost late 486 boards contain a lot of jumpers that need to be set correctly for the CPU to work correctly.

It's funny that your BIOS tries to "update ESCD" when it is stored in an UV EPROM. The ESCD ("extended system configuration data") is a dedicated area in a flash BIOS chip that contains a table of installed hardware. This data is dynamically generated during the POST and written using the usual flashing process. I wonder why anyone ever programmed a UV erasable EPROM chip with code that tries to do ESCD updates. The jumper manual indicates that JP13 should not be installed when an UV EPROM is installed, but I don't know whether the BIOS is able to read back the setting of this jumper. So either your EPROM contains a BIOS version that's not meant to be used in EPROMs, or the jumpering is wrong.

The jumpers are set according to this table, but that issue keeps happening sometimes. When I got the board at first the jumpers were messed up (configured as a non-enhanced 486 IIRC), now they're supposed to be correctly set.