68kMLA Classic Interface
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| New Project: Prodigy 040/060 Card | |
| Posted by: konrad on 2026-01-27 09:51:08 Has it ever been possible to overclock a 68020, or is it not worth it? Regarding the 68040 at 57 MHz, was it internally stable when it was running? | |
| Posted by: Oliver_A on 2026-01-28 00:11:23 Slowly delving into the Macintosh specific software support of the Prodigy. 😉  | |
Posted by: Arbee on 2026-01-28 13:44:30My theory is that, if an FPU exception (which is the actual behaviour of an LC040) causes a sad Mac on emulation, then something else is being done by the ROM beforehand in order to determine the CPU. But how does the ROM, then, can successfully distinguish between a full 040 and an LC040? I mean, you must probe the CPU in some way, it's nothing you can automatically retrieve from a table.Yeah. I had a similar problem with the '030 and it turned out that Apple was checking the internal details of the 680x0 coprocessor interface (there are coprocessor interface registers in the CPU address space). The coprocessor interface doesn't exist on the '040 so it's not that. The SuperMario code does the more expected "check if an F line trap happens on an FPU instruction" thing instead of the coprocessor interface, but that's clearly not all of how it checks for an LC040. | |
| Posted by: Oliver_A on 2026-01-28 16:09:33 Or, and it‘s a speculation on my side now, the ROM is actually right, and MAME generates a wrong exception stack frame. An 68LC040 generates a different kind of stack frame in case of a missing FPU than an 68030 or 020 executing a unimplemented coprocessor instruction. | |
| Posted by: aladds on 2026-01-30 00:27:46 Could FPU detection be different because the ROM has to detect it some other way, as many LC chips have a hardware bug: www.linux-m68k.org/faq/fpuemu.html | |
| Posted by: Arbee on 2026-01-30 19:26:52 It actually was nothing complicated, just an oversight in MAME's 680x0 differentiation. | |
Posted by: croissantking on 2026-02-08 17:40:28Slowly delving into the Macintosh specific software support of the Prodigy. 😉How’s this going? | |
| Posted by: Oliver_A on 2026-02-12 09:35:12 Stalling a bit, because I am on a business trip this week. Rest assured, once I have reached next milestone, I‘ll post an update here. 😉 | |
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