Re: Stealing a Great Idea from the 6600

Lawrence D'Oliveiro wrote:

On Sat, 20 Apr 2024 18:06:22 -0600, John Savard wrote:

Since there was only one set of arithmetic instrucions, that meant that
when you wrote code to operate on unsigned values, you had to remember
that the normal names of the condition code values were oriented around
signed arithmetic.

I thought architectures typically had separate condition codes for “carry” versus “overflow”. That way, you didn’t need signed versus unsigned versions of add, subtract and compare; it was just a matter of looking at the right condition codes on the result.

Maybe now with 4-or-5-bit condition codes yes,
But the early machines (360) with 2-bit codes were already constricted.