I recommend reading this: http://wiretap.area.com/Gopher/Library/Techdo … /Cpu/coproc.txt

stamasd wrote:

I recommend reading this: http://wiretap.area.com/Gopher/Library/Techdo … /Cpu/coproc.txt

It reccomends to use the 3C87-40 with the 386DX-40.
I mean, I read the Cyrix DLC having problem with the usual 387 so I imagine the 4C87DLC to be a customized version for the Cyrix but will it work with a Am386DX-40?

I am not aware of any incompatibilities between the Intel FPUs and the 486DLC, but what's funny is that certain versions of the DLC don't work with certain versions of Cyrix's own FPUs. No comment on IIT or ULSI.

Sure, the x87DLC badged FPUs might have updates to make them more compatible with DLCs, but I'm pretty sure the main reason they changed the naming scheme is because during the DLC days nobody was buying 386s anymore.

Anonymous Coward wrote:

I am not aware of any incompatibilities between the Intel FPUs and the 486DLC, but what's funny is that certain versions of the DLC don't work with certain versions of Cyrix's own FPUs. No comment on IIT or ULSI.

Sure, the x87DLC badged FPUs might have updates to make them more compatible with DLCs, but I'm pretty sure the main reason they changed the naming scheme is because during the DLC days nobody was buying 386s anymore.

I was thinking same thing too. 😉
Hope to try soon the speed of 1.5 frame for second in Quake! 😁

In FPU benchmarks there is no difference between IIT 387 and IIT DLC version.

I have a motherboard which requires you to set a particular jumper if you are using the 87DLC from Cyrix. If you don't set the jumper, it doesn't work. However, I haven't witnessed any speed differences between the Cyrix 387+ and the older grey-top Cyrix 387's. I suspect there may be some fixes for compatibility issues in all the various brands of the 387DLC's for use with DLC and SXL CPUs. I have witnessed some compatibility issues with certain programs when using an SXL2 and the older grey-top Cyrix 387's.

The best I've received in Quake is 3.1 fps with an SXL2-50.

Just don't go chasing after the clock doubled versions, not much performance gained and they are crazy expensive.

386SX wrote:

stamasd wrote:

I recommend reading this: http://wiretap.area.com/Gopher/Library/Techdo … /Cpu/coproc.txt

It reccomends to use the 3C87-40 with the 386DX-40.
I mean, I read the Cyrix DLC having problem with the usual 387 so I imagine the 4C87DLC to be a customized version for the Cyrix but will it work with a Am386DX-40?

My 386DX40 machine is working with an IIT 4C87DLC-40 at the moment. No problems at all (checked with old FORTRAN compilers and other ancient DOS software that utilizes it like matlab, etc.).

tayyare wrote:

386SX wrote:

stamasd wrote:

I recommend reading this: http://wiretap.area.com/Gopher/Library/Techdo … /Cpu/coproc.txt

It reccomends to use the 3C87-40 with the 386DX-40.
I mean, I read the Cyrix DLC having problem with the usual 387 so I imagine the 4C87DLC to be a customized version for the Cyrix but will it work with a Am386DX-40?

My 386DX40 machine is working with an IIT 4C87DLC-40 at the moment. No problems at all (checked with old FORTRAN compilers and other ancient DOS software that utilizes it like matlab, etc.).

Great! Which programs or games could I try to test it?

I really have no idea about any games that works on a 386DX-40 properly and utilizes a FPU at the same time. FPUs were expensive specialized items, and used mainly for ..well, floating point arithmetic. 🤣

I can only suggest AutoCAD (or many other old CAD software), FORTRAN compilers and math software like Matlab, Mathcad, Mathematica, etc. They were the ones I was using during the times.

Falcon 3.0 is a game that can use the FPU, and gives much better performance and enhanced graphics/simulation when an FPU is used.
It made a massive difference for me at the time when I had a 386SX-16 with an IIT387.

Scali wrote:

Falcon 3.0 is a game that can use the FPU, and gives much better performance and enhanced graphics/simulation when an FPU is used.
It made a massive difference for me at the time when I had a 386SX-16 with an IIT387.

It looks like a nice game! 😀

I tested the IIT 387 with Quake to see if it ran ok and .. it run.. 😁
But now I want to test more software on it.. it's nice to have it on my 386.

Scali wrote:

Falcon 3.0 is a game that can use the FPU, and gives much better performance and enhanced graphics/simulation when an FPU is used.
It made a massive difference for me at the time when I had a 386SX-16 with an IIT387.

I don't think Falcon 3.0 ran without a FPU or at least FPU emulator (like q387 or Frankie).

kixs wrote:

I don't think Falcon 3.0 ran without a FPU or at least FPU emulator (like q387 or Frankie).

Yes, it has an FPU and non-FPU mode. If you don't have an FPU, certain features are just simplified or not available, and performance is lower.
It was one of the first games to use an FPU. FPUs were certainly not widely available back the (and emulators are too slow, so not an option).
It can also use EMS, which again gives you some improvements in the game (I mainly recall that the videos would play more smoothly with EMS).

Is it normal that if I disable the Weitek processor enable function from the bios, it says "none" coprocessor at bios post and in the dos programs they see it correctly?

386SX wrote:

Is it normal that if I disable the Weitek processor enable function from the bios, it says "none" coprocessor at bios post and in the dos programs they see it correctly?

Probably. A Weitek coprocessor is an entirely different beast compared to a 387.
The BIOS POST may just indicate the Weitek setting, while DOS programs actually try to detect a 387 by executing FPU functions and checking if they work.
If DOS programs detect that an FPU is present, it is present.

Scali wrote:

Probably. A Weitek coprocessor is an entirely different beast compared to a 387. The BIOS POST may just indicate the Weitek sett […]
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386SX wrote:

Is it normal that if I disable the Weitek processor enable function from the bios, it says "none" coprocessor at bios post and in the dos programs they see it correctly?

Probably. A Weitek coprocessor is an entirely different beast compared to a 387.
The BIOS POST may just indicate the Weitek setting, while DOS programs actually try to detect a 387 by executing FPU functions and checking if they work.
If DOS programs detect that an FPU is present, it is present.

I never really heard about the Weitek, was that faster?

It was more specialized being optimized for single precision floating point.
https://micro.magnet.fsu.edu/optics/olympusmi … tekmathlow.html

gdjacobs wrote:

It was more specialized being optimized for single precision floating point.
https://micro.magnet.fsu.edu/optics/olympusmi … tekmathlow.html

"...Some experts believed that the Weitek silicon devices might have been even faster than the Pentium and some of the other more advanced personal computer microprocessors. However, utilizing system memory meant that an allocation of address space was required to properly use these Weitek coprocessor chips...

😲