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What is the best Mac ROM to use?

Posted: Sat May 09, 2020 12:47 pm
by starfiretbt
So I have been studying BasiliskII and I came across a site that offered a great number of Mac ROM's that can be used. Which one is the best for BasilikII? Should I use ROM's that are closest to the games I am playing, for example, a ROM from 1992 for a game released in 1992?
Also I see five different CPU types in BasiliskIIGUI. Do I switch to 68020 for older games that Basilisk can emulate and 68040 for newer games Basilisk can emulate? Also what is FPU?

Re: What is the best Mac ROM to use?

Posted: Sat May 09, 2020 7:35 pm
by 24bit
FPU is the Floating Point Unit, once on a separate chip like the Motorola 68881.
The Motorola 680X0 could load off math calculations to a dedicated number cruncher that way.
As for the ROM, I never saw an advantage in emulation using different ROMs like Performa or Quadra ROM.
Basilisk II does heavy patches when loading functions ROM, maybe one reason that usable Mac ROMs do not differ in use of Mac emulation.

Re: What is the best Mac ROM to use?

Posted: Mon May 11, 2020 4:44 am
by adespoton
Basilisk II was developed against two computers: the Performa 460? and the Quadra 650. ... Dk7QDyKPY/ outlines what ROMs will actually work. If you find something that doesn't line up, feel free to adjust the spreadsheet.

Note that the ROM you use does not reflect what gets emulated; if you use a ROM that's too different from your hardware configuration (eg Performa ROM when the gestalt ID is set to Quadra 650 and the CPU is set to 68030) things will break. The ROM just presents the toolbox and hardware initialization routines that were present with that particular ROM to the emulator, which then applies patches all over it to your modern hardware, based on the 650 toolbox placement. This means, for example, that Powerbook ROMs which have a different address layout for the toolbox will fail to even boot Basilisk II.

Generally, pretty much everything should be able to run with the Quadra 650 ROM, a Quadra 650 Gestalt ID, 68040 processor, and Mac OS 8.1. If it won't run with that, you're better off using Mini vMac to emulate a specific older Mac.

As an aside, the Motorola 68040 included the FPU on-chip, so ALL 040 processors handle FPU, a secondary co-processor wasn't needed.

Re: What is the best Mac ROM to use?

Posted: Tue May 12, 2020 7:21 pm
by starfiretbt
That guide is looks great. So if I used the right ROM and configure my BasiliskIIGUI to the appropriate settings then BasiliskII should run as good as it will get? Assuming I'm following a ROM and configuration without a known problem in the notes, such as in row 48 which is the Quadra 650.

EDIT: By the way, the column "supported memory" refers the the hard drives right? Is it okay to set MacOS RAM to 1024 and under JIT Compiler set Translation Cache Size to 16384?

Re: What is the best Mac ROM to use?

Posted: Tue May 12, 2020 8:43 pm
by adespoton
Supported memory means how much RAM the physical computer associated with that ROM could properly address. BII can address significantly more -- but that doesn't mean you *should* give it more.

JIT should probably be disabled these days; it only works on specific hardware/OS configurations, and is inherently more buggy than with it disabled. It's useful for older, slower x86-based computers that can't run the base emulator at full speed without significant effort. The cache has nothing to do with the emulated system, and is just the memory allocated on the host where translated instructions can be stored before they are executed.