| The only software compatiblity issue is the few programs that
did illegal calls to the OS that broke with the 1.2 release.
On the 500 and 2000, the 1.2 Kickstart is in ROM
On the 1000 it loads from disk into write-protected 256K RAM
(not part of the 512K chip memory)
The 1.1 Kickstart should be able to load from disk on the 500 and 2000,
not sure, since they haven't shipped yet. But can it be
write-protected after loading?
-dave
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| Re: .2
I very much doubt that the 500 and 2000 can write protect a version
of Kickstart read in to RAM. One of Commodore's major goals for the
new Amiga's was to cost reduce the machines. I read that the write
controlled Kickstart memory of the Amiga 1000 adds $200 to the retail
cost of the machine (yes, that figure DOES sound a bit high). So,
going to ROMs (I hope with sockets!) allows Commodore to save on
the cost of the machines.
Another (somewhat invisible) difference between the 500 and the other
machines is that it sounds like it has only one memory bus. On the 1000
and 2000, memory can either be on the chip bus or the processor bus.
Memory on the chip bus is called in Amiga terms "chip memory," while
memory on the processor bus is called "fast memory."
In graphics modes where the special chips in the Amiga have to cycle steal,
only accesses to chip memory cause the 68000 to stall. Fast memory never
has any contention problems. Most of the time there is no difference
between fast memory and chip memory because you have to be using some
pretty gee whiz features on the Amiga before it happens. (People can
see I spend most of my time talking to the workbench screen.)
The 500 (or at least I surmise) has only a chip bus, and thus all memory
is chip memory. This sounds like another cost reduction: Commodore doesn't
have to put the addition memory driving hardware in to the 500, and thus
saves in cost.
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