How does the Apple Emulator work?

[dommer]

Hi,

I have my little A500 here and I've heard it said a few times that "The Amiga was the Fastest Apple Computer ever made". So how does that even work?

I understand that they are both M68K based, but is it emulation or is it more like a KVM sorta deal? Would I be able to take advantage of that on my A500 or 2000?

Here is a video for reference:

[ Show youtube player ]

Thanks.

[Pyromania]

Apple II Forever!

I never actually owned one. Emulator is good though.

[nogginthenog]

It's not really an emulator. A patched copy of the Mac OS is running directly on AmigaOS.

As far as I know there is nothing like a VM for the Amiga. The hardware of some 030/040/060s support it.

[scuzz]

Hi

Better to use an Amiga cus its superior anyway. But if you must.



http://www.scuzzscink.com/amiga/scuz...ary18_2002.htm


http://www.scuzzscink.com/amiga/car_libs_007.htm


http://www.scuzzscink.com/amiga/car_...ar_jam_58c.jpg

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scuzz
http://www.scuzzscink.com/amiga/car_001.htm

[Galahad/FLT]

Originally Posted by dommer

Hi,

I have my little A500 here and I've heard it said a few times that "The Amiga was the Fastest Apple Computer ever made". So how does that even work?

I understand that they are both M68K based, but is it emulation or is it more like a KVM sorta deal? Would I be able to take advantage of that on my A500 or 2000?

Here is a video for reference:

[ Show youtube player ]

Thanks.

Basically its not really an emulator in the strictest sense, because it doesn't have to interpret the main processor because its the same as the Amiga, so the Mac code runs at the same speed on the Amiga.

Unlike the Atari ST and the Amiga, you couldn't bang the hardware directly on the Mac, because it didn't really have much in the way of hardware.

On Amiga or ST, if you wanted to change a colour, you could directly change the value in the hardware register instead of going through the system.

On the Mac, if you wanted to do the same, you had to go through the system, Apple didn't encourage nor want anyone to write directly to any hardware addresses, for the simple reason that if Apple changes the hardware, your programs will still work, because they are writing to the system which then interprets that for the hardware.

And because Mac programs don't bang the hardware, every program is system compliant which means that there are no issues with letting the code run on Amiga because there will never be any strange accesses to hardware that are not emulated.

So Shapeshifter patches all those system calls in MacOS to something that will work on Amiga hardware, and its all done transparently, as far as the Mac programs are concerned, they are running in the same environment as a real Mac, so there are few problems.

[dommer]

Originally Posted by Galahad/FLT

Basically its not really an emulator in the strictest sense, because it doesn't have to interpret the main processor because its the same as the Amiga, so the Mac code runs at the same speed on the Amiga.

Unlike the Atari ST and the Amiga, you couldn't bang the hardware directly on the Mac, because it didn't really have much in the way of hardware.

On Amiga or ST, if you wanted to change a colour, you could directly change the value in the hardware register instead of going through the system.

On the Mac, if you wanted to do the same, you had to go through the system, Apple didn't encourage nor want anyone to write directly to any hardware addresses, for the simple reason that if Apple changes the hardware, your programs will still work, because they are writing to the system which then interprets that for the hardware.

And because Mac programs don't bang the hardware, every program is system compliant which means that there are no issues with letting the code run on Amiga because there will never be any strange accesses to hardware that are not emulated.

So Shapeshifter patches all those system calls in MacOS to something that will work on Amiga hardware, and its all done transparently, as far as the Mac programs are concerned, they are running in the same environment as a real Mac, so there are few problems.

Oh shit hi galahad. Tis an honor.

Thanks. I'm relatively new to the amiga world and I'm trying to learn as much as I can!

[Paulee_Bow]

I was wondering how this worked. It’s very clever.

[RedskullDC]

Hi Galahad, et al.

Originally Posted by Galahad/FLT

So Shapeshifter patches all those system calls in MacOS to something that will work on Amiga hardware, and its all done transparently, as far as the Mac programs are concerned, they are running in the same environment as a real Mac, so there are few problems.

To elaborate slightly on Galahad's already eloquent answer ....


MAC OS makes use of a number of the 68K "Trap" vectors, effectively they make for very quick subroutine calls.


Programs on the earlier MACs (128K, +plus) were more likely to hit the metal directly, though that pretty much disappeared once the colour machines appeared, since the internal architecture was quite a bit different.
Apple also explicitly discouraged direct hardware programming by this point.


Cheers,
Red

[drHirudo]

Originally Posted by RedskullDC

Hi Galahad, et al.





To elaborate slightly on Galahad's already eloquent answer ....


MAC OS makes use of a number of the 68K "Trap" vectors, effectively they make for very quick subroutine calls.


Programs on the earlier MACs (128K, +plus) were more likely to hit the metal directly, though that pretty much disappeared once the colour machines appeared, since the internal architecture was quite a bit different.
Apple also explicitly discouraged direct hardware programming by this point.


Cheers,
Red

Commodore also discouraged direct bang of the hardware, but the clean way is so slow, you can't get decent scroll even on Amiga 1200 without locking the system and directly banging the hardware. Hopefully for the Mac, it didn't have many custom chips, so nobody was bothering doing something clever with them.