Re: architecture, The Design of Design

According to Scott Lurndal <slp53@pacbell.net>:

My impression is that until S/360 there was no such thing as different
by 100% SW compatible models.

>
The Burroughs B5500 and B3500 were contemporaneous with the S/360
and provided 100% SW compatible models across a performance range
during the same 1965 to 1978 time period as the S/360.

Wikipedia says that while S/360 and the B3500 were announced in 1964,
the B3500 was announced in 1966. In the discussion of MCP on the B3500
it says 'It shared many architectural features with the MCP of
Burroughs' Large Systems stack machines, but was entirely different
internally, and was coded in assembly language, not an ALGOL
derivative." That suggests it was compatible for user programs, but
not for operating systems.

On the 360, if two models had similar memory and peripherals, you
could IPL and run the same operating system since it was specified
down to the details of interrupts and I/O instructions.

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