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Comment by basementcat | Hacker News Reader

Do the '040/060 also support this "undocumented instruction"?

On the 040, it seems to do something that actually involves D1. Definitely doesn't touch A1 at all. I didn't test further, but it's possible it just handles the instruction as a normal CAS.

It did cause a system error the first time I stepped through the instruction with MacsBug on my LC 475, but then it was fine after that.

Have an Amiga w/ 060, and that instruction doesn't seem to modify any A registers. (Only did a very quick test of those exact instruction words)

I appreciate that I can ask an esoteric question about the behavior of a 30 year old microprocessor and multiple people respond with test results on actual hardware within a few hours. Can y'all also post the mask revision (if known) and whether it is an EC or LC device? (In case it impacts behavior)

Rev5 "full" 060 (not EC/LC). Quick capture of crappy methodology: https://imgur.com/a/XwQ1Tnp (PCR with revision number is in d0)

Today by, way of your screenshot, I discover Asm-Pro. Just got into Amiga recently (by way of receiving one from my uncle's closet..) and have been meaning to backfill my shameful lack of 68k asm knowledge. Thanks!

Good luck! As the sibling comment mentions, Asm-Pro is IMO a good choice these though it requires KSv2+ (so you can't use it on an stock A500). I mostly use vasm for "larger" stuff though (http://sun.hasenbraten.de/vasm/) and cross-compile (though it can run on Amiga as well) / test in an emulator.

For a quick test/code loop nothing beats the Asm-* family - remember to save often and make backups though :)

Asm-Pro is a modern, maintained, feature-rich asmone derivative.

Another modern/maintained one, focusing on low end 68000/68010 machines, is asmtwo.

AsmOne was a very popular assembler at the time, and has seen a few derivatives. I remember an old one called trash'm'one.

Update: a1=-1 is a bad choice of test value (0 is much better), as it won't show the issue if present! However, it doesn't change the outcome of the test on 060, but I would have noticed that 020 is affected as well (as also mentioned in the comments to the article).

My test of an 040 (no A1 change, D1 changed) was on a chip with the following markings:

XC68LC040RC25B

02E23G QEDP9348D MALAYSIA

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