05 March 2023, 22:45 | #81 |
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I don't think people understand how emulations work. The code for this integral, meaning that this affects the entire operation of the code. The problem is the Mac itself pokes at the MMU all of the time as part of its normal operation. This is also the case with standard Mac apps that bypass the OS routines to poke at the MMU. I have to trap and change any access to the MMU when there is an MMU present, and when there is no MMU present the CPU is suppose to fault and then that is trapped. With EMU68 there is no fault occurring because that is not supported apparently. Turning off the MMU means only 256K ROMs and no OS8.1. For FUSION this is normally not an issue because people always have a MMU present when there is a 68030/040/060 being used. There is no MMU or even basic support in EMU68, which means everything is much slower having to use 256K ROMs and constantly patching every single MMU operation on the fly. If the author of EMU68 would add the basic stuff that the Vampire and other things have, then this would not be an issue.
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05 March 2023, 23:37 | #82 | |
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Quote:
"FUSION *requires* a MMU when you are using a 68030 or later, OR the CPU can fault out correctly and continue with an EC030." Now I get it - thanks for the clarification. |
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09 March 2023, 05:16 | #83 | |
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Quote:
According to michalsc, Emu68's 68040 MMU feature is WIP. |
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13 March 2023, 12:14 | #84 |
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I have been in contact with Michal about this issue in recent days. The problem was actually discovered by him probably a year ago now. The Mac on boot up starts poking at the FPU and MMU to determine what types are being used. The 68020 Macs use the 68851 and the 030/040 had different MMU configurations. The only way to know what you are really using is by doing various instructions. This process causes EMU68 to crash. So, I need to go back in history (Discord) and find the screenshots that Michal made showing the issue - which at the time he said he zero interest in supporting. That apparently has changed if I can help him pin-point the issue(s). So, that's good news.
Of course, having a real (or correctly emulated) MMU is the way to go as that guarantees extremely high compatibility. It's the reason why FUSION runs so fast and stable on real hardware (and WinUAE). |
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