PlayRatty: Basilisk II PSP Port test release 18: new relaxed timing on 60Hz IRQ

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Basilisk II PSP Port test release 18: new relaxed timing on 60Hz IRQ

2008-07-16 02:03:51 by Charles D. in PSP Updates

Homebrew developer J.F. recently rolled out the latest test release for the PlayStation Portable-based Mac emulator, Basilisk II. The new build finally addresses the horrible slowdowns the emulator has been experiencing over the past versions.

The developer explained how test release 18 now forgoes clearing the 60Hz interrupt flag until after the Mac interrupt handler is done. This substantially reduces the lag time on the handheld as well as any tests done with the program's source code on the Mac.

Here's a brief rundown taken from the developer's thread, explaining the new changes added to the latest test release of Basilisk II since our previous coverage:

Test release 15

This fixes a few bugs - one in the imap/floppy/cdrom menu, I switched back to unix gettimeofday timing (seems a little more consistent), it should handle the caps lock key correctly, and should load IRDA.PRX on 3.80 .
I also fixed a minor quibble in the default input mapping - CROSS is now enter instead of keypad enter. I now allow for comments in the input maps. Look at the included default and Maelstrom maps as examples. Here's a tip for testing your input maps/keyboards - under the Apple Menu is a little jewel of an app called Key Caps... use it!

Test release 16

Made a few more changes to the timing, and now I support suspend/resume. The only thing that shouldn't work after resume is the network. I might add that later. I'm not very motivated on that front right now.

Test release 17

Only change is in the waits to trigger task switching.

Test Release 18

You'll notice the new PSP setting for relaxed timing on the 60 Hz IRQ. When enabled, the 60 Hz timer waits about 16 ms from whatever the time currently is, so you get the 60 Hz IRQ about 60 times a sec, but no guarantees. Disabled uses the default B2 code to try to maintain a drift-free 60 Hz interrupt. This naturally uses more time and can bog down the Mac depending on what else is going on. The default is relaxed timing, which is much smoother.

For more information, you can also check out the developer's release thread on the source site and leave any feedback you have there.

Download: Basilisk II PSP Port test release 18
Download: Basilisk II PSP Port test release 18 (source code)