68000 + 68881

Seiya · 29 April 2023, 12:19

in very old WinUAE release was possible to create configuration with 68000 + 68881, but in newer release this thing has been removed.

I know that 68000 has internal floating point emulation, but there are A500 expansion (not cpu accelerator) that have 68881 socket to use some software games and applications that are optimized for this unit.

As that in true Amiga 500 you can put 68881 with expansion card, it would be nice to have also in emulator this possibility.

Toni Wilen · 29 April 2023, 12:37

68000+6888x is only supported if no CE and more compatible. Hardware level 68000+6888x does not exists in real world (see below). Emulating it would require FPU emulation that uses 68000 prefetch pipeline which is not worth the trouble. (This combination has never been supported, or at least it has never been fully compatible)

This is not same as real 68000 + 68881 combination. Because 68000 does not have hardware co-op interface, extra software is needed (math libraries or similar comes with the board) that decodes FPU instruction, converts them to coprocessor interface commands, waits for response and decodes the response.

Basically it emulates 68020/030 co-pro hardware interface in software. It is most likely horribly slow.

EDIT: emulating co-pro interface in UAE is not going to happen. It is ultra-extremely-complex and not very well documented.

Seiya · 29 April 2023, 12:57

ok

29 April 2023, 12:19	#1
Seiya Registered User Join Date: Nov 2014 Location: Italy Posts: 2,373	68000 + 68881 in very old WinUAE release was possible to create configuration with 68000 + 68881, but in newer release this thing has been removed. I know that 68000 has internal floating point emulation, but there are A500 expansion (not cpu accelerator) that have 68881 socket to use some software games and applications that are optimized for this unit. As that in true Amiga 500 you can put 68881 with expansion card, it would be nice to have also in emulator this possibility.

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29 April 2023, 12:37	#2
Toni Wilen WinUAE developer Join Date: Aug 2001 Location: Hämeenlinna/Finland Age: 49 Posts: 26,526	68000+6888x is only supported if no CE and more compatible. Hardware level 68000+6888x does not exists in real world (see below). Emulating it would require FPU emulation that uses 68000 prefetch pipeline which is not worth the trouble. (This combination has never been supported, or at least it has never been fully compatible) This is not same as real 68000 + 68881 combination. Because 68000 does not have hardware co-op interface, extra software is needed (math libraries or similar comes with the board) that decodes FPU instruction, converts them to coprocessor interface commands, waits for response and decodes the response. Basically it emulates 68020/030 co-pro hardware interface in software. It is most likely horribly slow. EDIT: emulating co-pro interface in UAE is not going to happen. It is ultra-extremely-complex and not very well documented.

29 April 2023, 12:57	#3
Seiya Registered User Join Date: Nov 2014 Location: Italy Posts: 2,373	ok

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