> At 225 MHz an average 30.5 FPS with some rare 20-25 FPS are achieved when running 'timedemo demo3'. Resolution is the default Doom, 320x200.
> To reach the same performance on a PC something like a 486 @ 66MHz and a decent graphics card is needed.
Even accounting for the assembly optimizations, it sounds curious that the ZPU would do so much less work per cycle. Does anyone know why this might be?
PS. Doom 1 just used the standard VGA mode (13h), and the graphics card didn't matter much.
That struck me as very weird as well. I never heard of this CPU, so I looked it up. Turns out it's not supposed to go fast: the designers boast of a tiny implementation and dense code, and it only intended for "light administrative tasks".
The design is pretty neat. It's a stack machine, no registers, and literally a bytecode: each instruction is 1 byte long. The only exception seems to be a little hack in the IM (push constant) instruction to allow chaining to build long constants.
> To reach the same performance on a PC something like a 486 @ 66MHz and a decent graphics card is needed.
Even accounting for the assembly optimizations, it sounds curious that the ZPU would do so much less work per cycle. Does anyone know why this might be?
PS. Doom 1 just used the standard VGA mode (13h), and the graphics card didn't matter much.