Disabling the FPU doesn’t stop Quake from running
skitt opened this issue · comments
Describe the bug
Quake requires a FPU and on a real FPU-less system it aborts with “Error: Quake requires a floating-point processor”. Disabling the FPU in DOSBox-X doesn’t prevent Quake from running, I thought it would/should.
Steps to reproduce the behaviour
- Start DOSBox-X with
dosbox-x -set "cpu fpu=false" -set "cpu cputype=pentium" - Confirm that the logs show the corresponding warning: “WARNING: Disabling FPU support for this CPU type is unusual, may confuse DOS programs”
- NSSI and similar tools determine that there is no FPU
- Start Quake, it runs fine
Expected behavior
Quake should abort as described above.
What operating system(s) this bug have occurred on?
Debian 12
What version(s) of DOSBox-X have this bug?
2024.03
Used configuration
No response
Output log
No response
Additional information
I haven’t tried with FPU emulation disabled at build-time, see #4262
Quake (or rather, DJGPP) expects interrupt 7 to occur if it tries to run a floating-point instruction without a FPU. It seems this doesn’t happen on DOSBox-X.
Have you checked that no similar bug report(s) exist?
- I have searched and didn't find any similar bug report.
Code of Conduct & Contributing Guidelines
- I agree to follow the code of conduct and the contributing guidelines.
I'm able to cause Quake to crash by setting fpu=false.
That’s intriguing, I wonder what the difference is...
Visual Studio x64 version runs MCPDIAG regardless of fpu=true|false when CPU core is dynamic_x86.
If CPU core is normal and fpu=false, MCPDIAG mentions FPU is not available.
CPU core = dynamic_x86 and fpu=false
CPU core: normal and fpu=false
