Linked by Kroc on Thu 24th Aug 2006 20:26 UTC
OSNews, Generic OSes GEOS managed to offer nearly all the functionality of the original Mac in a 1 MHz computer with 64 Kilobytes of RAM. It wasn't an OS written to run on a generic x86 chip on a moving hardware platform. It was written using immense knowledge of the hardware and the tricks one could use to maximise speed. Note: After a small break, here is another one of the articles for the Alternative OS contest.
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JonathanBThompson
Member since:
2006-05-26

The Macintosh mutations that used the Motorola 68000 were not truly 32 bit processors: they had a 24 bit address bus, a 16 bit data bus, and also did have some instructions that would work on 32 bit data, but... they were not truly 32 bit processors. Were they better than the 8088/8086 available then? Most certainly! For a given clock speed (and the Macintosh started at about 8 Mhz) it was more efficient per clock cycle, and it also had more registers, but it still wasn't a true 32 bit chip.

Other than that, it was a great article.

Reply Score: 1

evilrich Member since:
2006-07-06

If you are going to nit-pick, please nit-pick with more accuracy. ;-)

> also did have some instructions that would work on
> 32 bit data

The 68000 was fully 32-bit internally. So, it wasn't just 'some instructions' that operated on 32-bit data, but most instructions since its general-purpose registers were all 32-bit.

Yes. It did have a 16-bit data bus and a 24-bit address range (the address bus was actually 23 bits wide - it took some extra magic to access odd addresses). Thus it was usually billed as a 16/32-bit CPU.

Reply Parent Score: 1

evilrich Member since:
2006-07-06

> The 68000 was fully 32-bit internally.

To nit-pick myself, that's not quite true, either. ;-)

The ISA was 32-bit, but the 68000 was mostly 16-bit internally.

Reply Parent Score: 1

viton Member since:
2005-08-09

> Motorola 68000 were not truly 32 bit processors:
Truly? There is no such things as truly or not truly cpu ^_^
68000 has full 32bit ISA (7 years ahead of intel), who cares what was under the hood? !!!
Do you need 32bit address bus for a couple of megabytes of RAM? NO!!! It would be just a waste of transistors.
32bit ALU did not fit in their transistor budget, so 32bit data was processed in 2 chunks in 16bit alu.

Pentium4 also has 16 bit ALU, so why you didn't call it 16 bit cpu????

Reply Parent Score: 1