24 Aug
2015
24 Aug
'15
1:51 p.m.
On Aug 22, 2015, at 10:31 PM, Chuck Guzis <cclist
at sydex.com> wrote:
On 08/22/2015 06:26 PM, Paul Koning wrote:
than the usual rule).
Well, we were always the guinea pig for QSEs in SSD. It's not described in the Cyber
70 docs, but we had Cybers fitted with the option. It did make its way into the 170s
however:
In 60456100A, re: the 42 instruction (page 4-24, second column):
"This instruction is used in multiple-precision floating-point calculations. This
instruction also provides for integer multiplication capabilities where both operands have
an exponent value of plus or minus zero and neither coefficient has been normalized. The
integer result sent to Xi is *48 bits with a 60-bit sign extension* (emphasis mine)."
Ok, but that is simply the standard 6000 series double multiply. That's not an
optional feature; the behavior you describe is how it always works and why IXX*X is a
synonym for DXX*X. All that's going on here is that the exponent field remains zero,
so it acts as an extended sign field.
paul
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.