March 6, 2012

Floating point, grayscale, scheduler, audio, and PS/2 keyboard?

While I haven't posted any updates lately, I've been working on Punix and occasionally posting my progress on the Cemetech forums.
I have also had family issues for the past few months now that have taken much of my free time.
Here's a summary of what I've done since last time:
  • M68881 FPU emulator is still under development, but a few instructions work well so far: fmove, fadd, fmul, fsub, fabs, and fneg. Execution speeds for fadd/fsub and fmul are faster than the equivalent operations in PedroM (which uses a slower BCD floating-point format to be compatible with TI-AMS).
  • Four-level grayscale! Currently only HW2 is supported, but that's probably more common than HW1 anyway. Text glyphs are also anti-aliased to take advantage of grayscale.
  • The scheduler has been tested quite thoroughly by now. I recently stress-tested it by running a few dozen busy processes at various "nice" levels, while also playing audio. Surprisingly, playing audio at the base nice level (zero) with 43 busy processes resulted in smooth, skip-free sound.
  • I'm playing with the idea of adding a PS/2 driver which will allow a user to plug a regular keyboard into the link port (with an appropriate adapter) and start typing away on it. This is a low-priority feature, but I'm the most excited about it at the moment.

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