amiga-news.de - Motorola68k emulation: Emu68 V1.0 Release Candidate

22.Sep.2023 Motorola68k emulation: Emu68 V1.0 Release Candidate
A month ago, Developer Michal Schulz had released beta version 2.1 of his Motorola68K emulation Emu68 for the ARM architecture, focusing on the PiStorm and PiStorm32lite (amiga-news.de reported). Since then, many other improvements have been added. Changes of the release candidate of version 1.0:

BFxxx updated

The bitfield instructions operating on memory are not optimized to use as little memory accesses as possible. There are still corner cases which will do more traffic than necessary, but they are now very limited. The bitfield instructions will fetch byte/word/long word/quad word instead of always working on quad words.

Better write to CHIPSET registers

After a write to memory area belonging to Amiga chipset, a byte read from ROM is issued. This improves stability of some old games/demos which never assumed to be running on m68k which is that fast. A read from ROM gives Paula enough time to complete the interrupt acknowledgment properly.

IPL filter

Emu68 filters the IPL lines and recognizes an IPL change if and only if two subsequent IPL reads (which are roughly 400 nanoseconds away) give the same result. Improves many games or demos which suffered from spurious interrupts.

Write buffer removed

The write buffer was my experiment introduced quite long time ago - it featured a write combining to subsequent byte/word locations as long as they would finally result in a longword write cycle. It worked relatively well in most cases, but failed miserably in some others. Since this was just a dirty hack, it has been removed now.

CCR optimizer scan depth

The number of m68k opcodes which are scanned in-advance during m68k to arm translation for elimination of CCR flag updates is now adjustable. Use EmuControl version 1.3 for that (nightly build from 23. Sept. 2023 or newer).

The developer provides more detailed information on the changes in his new Patreon post. (dr)

[News message: 22. Sep. 2023, 21:52] [Comments: 0]
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