I was wondering what the IBM Personal Computer would have been like if they had chosen the Motorola 68000 instead of the Intel 8088, so I used my MCL86+ to emulate the 68000 and find out!
The MCL86+ is a board which uses a Teensy 4.1 to emulate a microprocessor in C code as well as use its GPIOs to emulate the local bus of the Intel 8088. It can be used as a drop-in replacement for the Intel 8088 and can be cycle accurate as well as run in accelerated modes.
That’s a neat trick.
I’m not surprised, and I’ll also add I wouldn’t be surprised that if IBM had used the 8086 and had 16-bit paths on the bus, it would have been similar performance also (but faster). Really the main speed killer was the 8-bit bus, which brought down the performance of the PC to that of a good Z80 based system. These were competitive speed-wise until the price of RAM came down enough to take advantage of the larger address space in the 8086/8088 architecture which made 64K seem rather cramped. 8-bit only machines like the Z80 and 6502 of course had bank switching since forever, but software had to be hardware specific to take advantage of that.
According to Gates, they didn’t go with 68000 because it wasn’t ready. But interesting to see it wouldn’t have been that different performance wise. Also, they wanted a low end machine to avoid cutting into their other machines business segments..