Are you saying you can install NT 3.5 but after running though setup it does not boot?
or that you are unable to even boot off the floppy to start the setup process?

Also found this https://www.quora.com/Why-should-you-not-inst … ium-4-processor
Relevant post below

First of all, none of Windows NT 3.1, 3.5 or 3.51 officially support anything beyond the original Pentium processor. There is a block in place in the setup program to disallow installing on any unrecognized processors. (The Pentium 4 was introduced several years after NT 3.51.)

You can work around this by manually editing the setup files (there’s a SETUP.INI property called STF_PROCESSOR that determines what processors are allowed).

But then you’ll run into another problem — NT before version 4 doesn’t support more than 64MB of RAM. By the time the SiS 645-based Pentium 4 motherboards that supported SDRAM came out in early-mid-2002, 256MB of RAM was pretty standard for workstation-class Windows systems.

So if you need a reason to not install NT 3.51 on a Pentium 4, it’s because you wouldn’t be able to use most of the memory you could install on it.

Okay, okay….. there is a way around this, which is to copy the NTLDR file from a Windows NT 4.0 system to an NT 3.51 system…. this will allow more memory to be seen.

That still won’t make Windows NT 3.51 use the many performance improvement that are present in the newer CPUs, so it’s going to be noticeably slower than Windows 2000 or even NT 4.0 on the same hardware.

chinny22 wrote on 2023-05-24, 09:07:

Are you saying you can install NT 3.5 but after running though setup it does not boot? or that you are unable to even boot off t […]
Show full quote

Are you saying you can install NT 3.5 but after running though setup it does not boot?
or that you are unable to even boot off the floppy to start the setup process?

Also found this https://www.quora.com/Why-should-you-not-inst … ium-4-processor
Relevant post below

First of all, none of Windows NT 3.1, 3.5 or 3.51 officially support anything beyond the original Pentium processor. There is a block in place in the setup program to disallow installing on any unrecognized processors. (The Pentium 4 was introduced several years after NT 3.51.)

You can work around this by manually editing the setup files (there’s a SETUP.INI property called STF_PROCESSOR that determines what processors are allowed).

But then you’ll run into another problem — NT before version 4 doesn’t support more than 64MB of RAM. By the time the SiS 645-based Pentium 4 motherboards that supported SDRAM came out in early-mid-2002, 256MB of RAM was pretty standard for workstation-class Windows systems.

So if you need a reason to not install NT 3.51 on a Pentium 4, it’s because you wouldn’t be able to use most of the memory you could install on it.

Okay, okay….. there is a way around this, which is to copy the NTLDR file from a Windows NT 4.0 system to an NT 3.51 system…. this will allow more memory to be seen.

That still won’t make Windows NT 3.51 use the many performance improvement that are present in the newer CPUs, so it’s going to be noticeably slower than Windows 2000 or even NT 4.0 on the same hardware.

i have some apps that wont work on nt 4.0, and i want to try 3.5, but im struggling with my bios update, my bios seems to be write protected and i cant update.

https://www.youtube.com/watch?v=QVdW_SQG5ZY