> On Oct 3, 2024, at 12:01 PM, CAREY SCHUG via cctalk <cctalk@classiccmp.org>
> wrote:
>
> I worked on a model 1 with 40k memory (my very first computer experience) and
> floating point, and later a model 2 stripped. I believe the model 2 still
> used table lookup for multiply.
Sure enough, that's what the Model 2 manual I just found on Bitsavers says. I
always though that both add and multiply were in hardware. Interesting.
Another major enhancement in model 2 is index registers.
> floating point in model 1 (and I think model 2) was limited to a 98 digit
> mantissa, still more precision than the hardware in any subsequent computer
> AFAIK. since the exponent was 10**-99 to 10**99 a broader range than any
> computer till many years later I think.
100 digits says the model 2 manual.
Exponents larger than that do appear in machines of that era. The CDC 6000
series goes up to 10**322 (11 bit signed binary exponent) and the Electrologica
X8 to 10**644 (12 bit signed binary exponent). Both are early 1960s. I don't
remember what the IBM 360's range is; the exponent field is fairly small but
it's a power of 16 rather than the usual power of 2 (or power of 10 as in the
1620).
> ...
> don't know if the disk i/o RPQ overlapped, I saw one through a glass window
> once.
No, just like all the other I/O instructions they block the CPU.
paul
