23 Aug
2015
23 Aug
'15
1:26 a.m.
On Aug 22, 2015, at 9:15 PM, Chuck Guzis <cclist at
sydex.com> wrote:
On 08/22/2015 04:40 PM, Paul Koning wrote:
I recall the "integer multiply" feature (i.e. optional) available on the 6000.
IXi Xj*Xk, but it didn't provide any more precision than the usual unnormalized
double-precision multiply DXi Xj*Xk, but saved some time spent fiddling with exponent
fields.
??? Never heard of any such thing. IXi Xj*Xk is a defined opcode, but it's simply a
synonym for Dxi Xj*Xk.
paul
On Aug 22, 2015, at 6:27 PM, Chuck Guzis
<cclist at sydex.com> wrote:
...FLoating point can engender some interesting representations.
Consider the exponent field on the aforementioned CDC 6000 series.
It's a "biased by 2000 octal) system--and the assumed binary point
of the mantissa is to the right of the LSB. So, 2000 0000 0000
0000 0001 octal = 1 exactly.
EL-X8 doesn't use the bias, so the floating point representation of
an integer under 2^39 is the same as the integer representation. And
the rule for normalizing float values preserves that (normalization
makes the exponent as close to zero as possible -- rather different
than the usual rule).