That stack of documents next to Margaret Hamilton could easily be multiple iterations of the source code, the kind of thing where every month or so you print the whole source for reference. We were still doing that in the early 80s.
Also, I think she worked in the MIT Instrumentation Lab rather than directly for NASA.
Nice write up. I never noticed the connection between five bit characters and seven bit ascii.
This is a great article, thank you for the care with which you examined our history! I think we need to be careful when we say that a processor "is" n-bits, or even retire the phrase, as evinced by:
> Motorola shipped the 68000 (68k) CPU in 1979. Technically, it was a 16-bit processor like Intel’s competing 8086, but it made the radical decision to have 32-bit registers.
It sounds like although the instruction set operates on 32-bit words, the registers are 32 bits wide, and the address bus is 24 bits wide, because the data bus is 16 bits wide and the ALUs are 16 bits wide, the processor is described as "a 16-bit processor". But the 68008 has the same instruction set, with 20 address bits and 8 data bits, is that "an 8-bit processor"?
The CPU had 16-bit ALUs, making it a 16-bit CPU. The external bus didn't matter. People only ever cared about the ALU width in defining whether something was an "8-bit", "16-bit", or "32-bit" processor.
This is mostly because most of the time, it's operating on registers. Therefore, memory width matters less than ALU width.
That stack of documents next to Margaret Hamilton could easily be multiple iterations of the source code, the kind of thing where every month or so you print the whole source for reference. We were still doing that in the early 80s.
Also, I think she worked in the MIT Instrumentation Lab rather than directly for NASA.
Nice write up. I never noticed the connection between five bit characters and seven bit ascii.
This is a great article, thank you for the care with which you examined our history! I think we need to be careful when we say that a processor "is" n-bits, or even retire the phrase, as evinced by:
> Motorola shipped the 68000 (68k) CPU in 1979. Technically, it was a 16-bit processor like Intel’s competing 8086, but it made the radical decision to have 32-bit registers.
It sounds like although the instruction set operates on 32-bit words, the registers are 32 bits wide, and the address bus is 24 bits wide, because the data bus is 16 bits wide and the ALUs are 16 bits wide, the processor is described as "a 16-bit processor". But the 68008 has the same instruction set, with 20 address bits and 8 data bits, is that "an 8-bit processor"?
The CPU had 16-bit ALUs, making it a 16-bit CPU. The external bus didn't matter. People only ever cared about the ALU width in defining whether something was an "8-bit", "16-bit", or "32-bit" processor.
This is mostly because most of the time, it's operating on registers. Therefore, memory width matters less than ALU width.