9 Dec
2005
9 Dec
'05
5:54 p.m.
On 12/9/2005 at 7:35 AM Allison wrote:
The other differences were internal effective address
calculation was
handled
differntly from 8088 which shaved a few cycles of the execution. For the
same clock V series were between 5-10% faster. Also the V20/V30 had 8080
emulation.
Hmmm, thought I just said that. One of the more highly-touted performance
improvements in the V20/V30 was the implemenation of dual internal data
busses. In practice, I don't know if it made a huge difference in speed,
but NEC claimed up to a 30% improvement for som operations..
FWIW, my reference manual for the 70108/70116 is dated August 1985 and
identifies both as "Low Power CMOS"; no mention otherwise of any other fab
technology. NEC did later offer the -H series variants (V20H, V30H, etc.)
which featured fully static operation and lower power consumption than the
V20/V30--and you could get them in clock speeds of up to 16 MHz.
I've got a reasonably thick folder in my files titled "Natick" with a bunch
of correspondence with the NEC folks there on the whole subject. The V40,
which was sort of an 80188 in CMOS (PGA, QFP and PLCC pacakges) also
claimed to emulate the 8080 instruction set, but I never got hold of one to
try it out (or I didn't care to).
I thought it interesting that the 8080 emulation of the V20/V30 emulated
the Intel 8080A and not tne NEC 8080A instruction set.
Cheers,
Chuck