[COFF] GE-635 GECOS?

[Paul Winalski via COFF]

On Sat, Apr 4, 2026 at 9:42 AM Douglas McIlroy via COFF <coff at tuhs.org>
wrote:

> IBM had been ruled out over the issue of virtual memory. GE was happy
> to offer a VM variant of the 635. In contrast, IBM's chief architect,
> Gene Amdahl, adamantly maintained that VM was unacceptably
> inefficient.
>

Gene Amdahl was a notorious opponent of the concept of virtual memory.  He
famously stated that virtual memory merely magnified the need for real
memory.

Amdahl also had big fights with Fred Brooks over the word size for S/360.
Brooks insisted that the machine word size be a power of two.  Amdahl
favored a 24-bit design.  They eventually compromised:  the word size,
registers, and arithmetic operations on S/360 would be 32-bit but the
addressing would be 24-bit (16 MB).  Given that the biggest main storage
ever shipped on a S/360 was 8 MB,  24-bit address circuitry was more than
adequate and reduced the manufacturing costs for the machines significantly.

-Paul W.