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I'm a huge 68000 fan (I am happy it helped make the programmer I am today), but support for virtual memory was hardly the reason IBM selected the 8088 over the

by bcrl 6y ago

I'm a huge 68000 fan (I am happy it helped make the programmer I am today), but support for virtual memory was hardly the reason IBM selected the 8088 over the 68000 for the PC. Looking back at the history of 68000 based computers in the 1980s, there were so many missed opportunities. Both Commodore and Apple could have shipped systems with higher clocked 68000s in 1985, but didn't. Commodore didn't ship a real 32 bit system (the Amiga 3000) with the 68030 until 1990, 3 years after the 68030 was released in 1987. Apple at least shipped the IIx in 1988, but it was priced so high as to not be a real option in the home market. In contrast, anything Intel shipped was brought to market far more quickly thanks to the booming clone market. There was even quite a bit of innovation in external caches for 386 and 486 based systems - I remember reading reviews in Byte magazine in 1987 highlighting the performance differences of the same CPU in a wide variety of systems. The 68000 series had so many architectural advantages over 8086/8088, but that one choice by IBM for the PC effectively doomed m68k to the dustbin of history. That still makes me sad to this day.

Gibbon1 6y ago
Two explanations I read in the late 80's. When the decision was made you had the 8088 and the 68000. 8088 had an 8 bit bus and needed 8 DRAMs. 68000 had a 16 bit buss and needed 16. And memory was about half the cost of a PC. So the 8088 minimum BOM was cheaper. Second I think the 8088's instruction set was designed to make porting 8080/Z80 assembler easy. I can't say that was important in practice once things were bootstrapped. But might have got them to market faster. I also think partly the dominant OS in the late 70's was CPM which ran on Intel/Zilog processors. 8088 was of course the manufacturer of the 8080. And my experience with Motorola in the 80's is they weren't exactly eager to sell into smaller markets. Of course now Intel is far worse and has been for the last 35 years.
- dboreham 6y ago
  68k was too new, too large a die (lots of articles at the time saying it might be unmanufacturable due to low yield) too costly.
- snvzz 6y ago
  68008 (1982) had 8bit bus, and some 68000 versions were made much later which supported both 8 and 16bit bus. But of course, this was way too late for IBM PC (released 1981).
cmrdporcupine 6y ago
808x also had architectural consistency/continuity with the popular CP/M systems that already existed. 68000 had continuity with nothing. Motorola had a habit of throwing away architectures when the new thing came out. 6809 was only assembly level compatible with the 6800. 68000 was completely different than the 6809 & 6800. They pushed the 88000 as the new hotness to Apple, NeXT, etc. but it was a total failure and the new hotness became PowerPC. At no point was there backwards compatibility. Apple had to engineer their own solution for 68k -> PowerPC migration, and it was crashy. Intel just kept plodding along with the x86 instruction set forever, keeping customers in a constant -- if ugly -- upgrade chain, until they made the Motorola mistake with Itanium. They smartly backpedaled from that, though. 68k still had half a chance in the late 80s, early 90s -- not to own the whole market, but to have a crack at a segment of it but Motorola flubbed it. Coldfire is really good, but was too late, inconsistent with their PowerPC strategy, and targeted towards the embedded market.
- mark-r 6y ago
  The 68000 was so powerful that I'm sure porting assembler to it from 8080/Z80 wouldn't have been a big deal. What was the timing between Coldfire and Arm? It's interesting to see how history turned on that axis too.
Animats 6y ago
Not IBM. The Macintosh. The Macintosh came out with a good GUI bolted onto a DOS-type OS. No processes, no threads, no swapping, no paging, no hard drive. The Lisa had all of that, but cost too much. However, it was actually useful. The Mac was a money-losing toy until it got better hardware, especially a hard drive and more memory, in the form of the Macintosh SE. But then Apple was tied to an OS cut down to fit the original 128K floppy-only machine. Which they stayed with far too long.
- bcrl 6y ago
  It was IBM that built the IBM PC that lead to the market for Intel x86 CPUs in clones. The Mac, Amiga, Atari ST, Sun... all of these combined were not enough to support Motorola with the resources needed to keep developing the 68000 series.
LargoLasskhyfv 6y ago
I remember reading reviews of some overengineered Compaq 386-SX with cache onboard :)

by bcrl 6y ago

Gibbon1 6y ago

Two explanations I read in the late 80's. When the decision was made you had the 8088 and the 68000. 8088 had an 8 bit bus and needed 8 DRAMs. 68000 had a 16 bit buss and needed 16. And memory was about half the cost of a PC. So the 8088 minimum BOM was cheaper. Second I think the 8088's instruction set was designed to make porting 8080/Z80 assembler easy. I can't say that was important in practice once things were bootstrapped. But might have got them to market faster. I also think partly the dominant OS in the late 70's was CPM which ran on Intel/Zilog processors. 8088 was of course the manufacturer of the 8080. And my experience with Motorola in the 80's is they weren't exactly eager to sell into smaller markets. Of course now Intel is far worse and has been for the last 35 years.

dboreham 6y ago
68k was too new, too large a die (lots of articles at the time saying it might be unmanufacturable due to low yield) too costly.
snvzz 6y ago
68008 (1982) had 8bit bus, and some 68000 versions were made much later which supported both 8 and 16bit bus. But of course, this was way too late for IBM PC (released 1981).

cmrdporcupine 6y ago

808x also had architectural consistency/continuity with the popular CP/M systems that already existed. 68000 had continuity with nothing. Motorola had a habit of throwing away architectures when the new thing came out. 6809 was only assembly level compatible with the 6800. 68000 was completely different than the 6809 & 6800. They pushed the 88000 as the new hotness to Apple, NeXT, etc. but it was a total failure and the new hotness became PowerPC. At no point was there backwards compatibility. Apple had to engineer their own solution for 68k -> PowerPC migration, and it was crashy. Intel just kept plodding along with the x86 instruction set forever, keeping customers in a constant -- if ugly -- upgrade chain, until they made the Motorola mistake with Itanium. They smartly backpedaled from that, though. 68k still had half a chance in the late 80s, early 90s -- not to own the whole market, but to have a crack at a segment of it but Motorola flubbed it. Coldfire is really good, but was too late, inconsistent with their PowerPC strategy, and targeted towards the embedded market.

mark-r 6y ago
The 68000 was so powerful that I'm sure porting assembler to it from 8080/Z80 wouldn't have been a big deal. What was the timing between Coldfire and Arm? It's interesting to see how history turned on that axis too.

Animats 6y ago

Not IBM. The Macintosh. The Macintosh came out with a good GUI bolted onto a DOS-type OS. No processes, no threads, no swapping, no paging, no hard drive. The Lisa had all of that, but cost too much. However, it was actually useful. The Mac was a money-losing toy until it got better hardware, especially a hard drive and more memory, in the form of the Macintosh SE. But then Apple was tied to an OS cut down to fit the original 128K floppy-only machine. Which they stayed with far too long.

bcrl 6y ago
It was IBM that built the IBM PC that lead to the market for Intel x86 CPUs in clones. The Mac, Amiga, Atari ST, Sun... all of these combined were not enough to support Motorola with the resources needed to keep developing the 68000 series.

LargoLasskhyfv 6y ago

I remember reading reviews of some overengineered Compaq 386-SX with cache onboard :)