12 Apr
2007
12 Apr
'07
8:17 a.m.
Jim Battle <frustum at pacbell.net> wrote:
Mike, your web page says:
"The System/370 processor is implemented in three microprocessors --
two Motorola 68000 processors and a custom 8087."
Are you sure about that? Nick Tredennick, the architect (or maybe co
architect) of the 68000 left Motorola, went to work for IBM, and was the
architect of the "micro 370". [...]
I know nothing of the machine you have there, but I suspect it is really
using redundant copies of the micro 370 described in the book. [...]
This quote from the article "System/370 capability in a desktop Computer"
(IBM System Journal Vol 23, No 2, 1984), may help resolve this issue:
As previously mentioned, three microprocessors are used to implement
System/370 processing functions. A custom-developed System/370
Subset microprocessor performs most of the System/370 commercial
instructions. Floating point, including extended precision, instructions
are executed by a custom developed Floating point microprocessor
which works in close conjuction with the System/370 Subset processor.
The remaining instructions are emulated by an MC68000R microprocessor
which also performs other tasks such as exception handling.
Having said that, I also remember reading somewhere about the 68000
with modified microcode somewhere (maybe Byte magazine?)
**vp