7 Aug
2006
7 Aug
'06
5:12 a.m.
On Sun, 06 Aug 2006 22:41:36 -0400 and Sun, 06 Aug 2006 22:47:23
-0400, Ray Arachelian <ray at arachelian.com> wrote:
Absolutely. The 68000 is an amazing little chip when
you compare
it to
the 6800 and 6502's that it evolved itself from. You can sort of
get a
feel from this from this journal:
It's worth a read to get a feel of the excitement the 68K caused
back in
the day when it was introduced. Some of it is very funny, there's one
issue where the author compares an Intel FPU to the 68000 running
software floating point routines, and guess what, the 68000
actually ran
FASTER! :-)
The excitement was for a good part due to the excellent marketing on
the part of Motorola.
Tony Duell wrote:
In the early '80s we started development of a process controller and
evaluated the 68K as well as the National 32K processor which had
been just released. The NS 32K processor was released with a FP unit
which we required while Moto didn't get around to getting one to
market for another year - the 68K on software just didn't hack it. We
went with the NS 32K and were quite pleased with the beast.
It was a true 32 bit processor witch came in three flavors: 8 bit, 16
bit, and 32 bit external busses - you could move the code from one to
the other with almost no change. The instruction set was extremely
orthogonal and close to those of the VAX sans the three operand
instructions. The only flaw we noted was that the entire machine
state was not saved on interrupt/trap which made a couple of features
useless.
The floating point processor was not a co-processor ala the 68K, but
a external instruction execution module. When the FPU was attached,
the FP instructions became active and you worked between internal
register pairs. IIRC they also made communication processor that
implemented part of the unimplemented instruction set. I played with
my own external processor to implement macro instructions that were
used to optimize execution time.
When Apple was evaluating processors for the Mac, an internal source
told me that NS marketing only made a half*** effort to sell the
part. Unfortunately NS did their normal thing when it came to
processors and shot themselves in the foot (see PACE - both
Studebaker and NS screwed those up) by trying to keep it all to
themselves. Consequently, there was little third party support for
the chip. I believe it to be a better implementation than the 68K.
CRC
That very much depends on the CPU. If the CPU is
many chips (not a
single
package) with microcode in PROMs, there's nothing to stop you
desoldering
said PROMs and reading them out. I've done that, then written a
disassembler for the microode instructions and worked out what was
going on.
True, but you don't find CPU's made of discrete logic these days,
so it
makes it very difficult to get at the microcode. 
7 Aug
7 Aug
12:16 p.m.
On 8/7/2006 at 2:12 AM CRC wrote:
In the early '80s we started development of a
process controller and
evaluated the 68K as well as the National 32K processor which had
been just released. The NS 32K processor was released with a FP unit
which we required while Moto didn't get around to getting one to
market for another year - the 68K on software just didn't hack it. We
went with the NS 32K and were quite pleased with the beast.
I'll concur with your assessment of the NS 32K processors and the huge
marketing mess they made of it. We'd evaluated the 8086, 68K and Z8000 and
were very excited to see a processor with a well-thought out architecture
like the NS 32K. We were pitched by NS's marketing, only to discover that
the chips would be sampled "Real Soon Now". After awhile, our decision
window passed and we selected the 80186 (of which Intel was delighted to
supply us samples of well in advance of the official release, bugs and
all). NS's sales force remained generally opaque and ignorant. It's no
wonder that for many years the only thing that kept National going was
second-sourcing of commodity chips.
I used to have a CPU S100 board that I built for the National PACE. That
CPU was a catastrophe. So slow and with very little NS support. Given
its very early introduction, it could have been a comer had NS taken any
interest in it. But at the time, NS was pushing the SC/MP and signing
second-sourcing deals.
Anyone remember AMC? A coop venture of AMD and Siemens (and maybe another
firm) to push the Z8000 with development tools? I still have a binder full
of documentation for their assembler. IIRC, it didn't last long.
Cheers,
Chuck
1:18 p.m.
CRC wrote:
On paper, a *delightful* processor (chip set). Unfortunately,
NS went on to develop the rest of the family (332, 532, etc.)
without real concern for fixing some of the blemishes in the
original parts (N.B. the original part was the 16032 -- later
renamed 32016 :> I think I still have a databook with *that*
on it's title page)
Ray Arachelian <ray at arachelian.com> wrote:
The excitement was for a good part due to the excellent marketing on the
part of Motorola.
And, motogorilla lined up LOTS of second-sources for the part
(IIRC, *8*?) -- though they didn't all source the other devices
(e.g. '010). Back then, having a second source was good
insurance -- nowadays, I don't think ANYTHING is second
sourced at a drop-in replacement level... :-(
Tony Duell
wrote:
In the early '80s we started development of a process controller and
evaluated the 68K as well as the National 32K processor which had been
just released. The NS 32K processor was released with a FP unit which we
required while Moto didn't get around to getting one to market for
another year - the 68K on software just didn't hack it. We went with the
NS 32K and were quite pleased with the beast. That very much depends on the CPU. If the CPU is
many chips (not a
single
package) with microcode in PROMs, there's nothing to stop you
desoldering
said PROMs and reading them out. I've done that, then written a
disassembler for the microode instructions and worked out what was
going on.
True, but you don't find CPU's made of discrete logic these days, so it
makes it very difficult to get at the microcode. It was a true 32 bit processor witch came in three
flavors: 8 bit, 16
bit, and 32 bit external busses - you could move the code from one to
the other with almost no change. The instruction set was extremely
orthogonal and close to those of the VAX sans the three operand
instructions. The only flaw we noted was that the entire machine state
was not saved on interrupt/trap which made a couple of features useless.
And, the MMU was an amusing "sit-alongside" implementation...
add it and a clock cycle to accesses and you get a two-level
paged MMU. With a small PLA, you could even design the
glue logic to allow the device to be "transparently" added
to the circuit without having to cut foils, etc.
The floating point processor was not a co-processor
ala the 68K, but a
external instruction execution module. When the FPU was attached, the FP
instructions became active and you worked between internal register
pairs. IIRC they also made communication processor that implemented part
of the unimplemented instruction set. I played with my own external
processor to implement macro instructions that were used to optimize
execution time.
The FPU was a bit minimalist. Very different approach from
Intel's x87 or AMD's 9511? (I forget the P/N). It wasn't
do "kitchen sink" but, rather, just concentrated on basic
support for floats (w/o things like transcendentals).
Since it was so minimalist, you didn't NEED to have the
FPU running "in parallel" with the CPU (a la x87 -- which
could be grinding away for a LONG time on transcendental
evaluation). It made writing real-time kernels easier
since you didn't have to reschedule support for FPU
context saves independant of the CPU's state.
When Apple was evaluating processors for the Mac, an
internal source
told me that NS marketing only made a half*** effort to sell the part.
Unfortunately NS did their normal thing when it came to processors and
shot themselves in the foot (see PACE - both Studebaker and NS screwed
those up) by trying to keep it all to themselves. Consequently, there
was little third party support for the chip. I believe it to be a better
implementation than the 68K.
NS was ALWAYS stupid in their marketing of processors!
Their GNX tools were pretty respectable, though (one of the
reasons I wanted to get my Opus PM back up and running was
to have access to that tool suite). OTOH, their ICE was
almost laughable -- almost the size of an EXORMACS/desktop PC!
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