CDC 6600 - Why so awesome?

Charles Anthony at
Tue Jun 21 16:27:11 CDT 2016

On Tue, Jun 21, 2016 at 2:06 PM, Swift Griggs <swiftgriggs at> wrote:

> - It was RISC nearly before folks could even articulate the concept
> - It used odd sized (by todays standards) register, instruction, and bus
>   sizes. 60 bit machine with 15/30 bit instructions. But, didn't it cause
>   a bunch of alignment issues for you ?
> I dug into the CPU instructions for about 20 minutes and it was actually
> pretty straightforward. The so-called "COMPASS" ASM code was oh-so-cool. I
> can't believe they had so many of the features now considered "modern" or
> "clever" (at least by me) in the 1960s! This code:

The odd thing about the instruction set is that it did not have
load/store instructions; load/store was a side-effect -- net register
An (for n in 0-5), and the data at the memory address the register was
set to was loaded into the corresponding Xn register, for n 6 or 7,
the value in the Xn register was stored at the address.

So the extra credit exercise is to figure out how to write a
subroutine that prints out the value of all of the registers; ie. how
can you save *all* of the register values to memory?

-- Charles

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