On 2015-07-09 02:16, Robert G. Schaffrath wrote:
On Jul 8, 2015, at 8:10 PM, Johnny Billquist <b...@softjar.se> wrote:
On 2015-07-09 01:57, Robert Armstrong wrote:
I haven't found microcode sources or listings for the 750, 730,
MicroVAX I, or 8600, for example.
FWIW, the 725/730 was somewhat unique in that the micro store was entirely
RAM. All of the microcode was loaded by the CFE at power on and none was in
ROM. Also, the 730 micro engine was based on industry standard 29xx family bit
slice parts. It was a little like the 11/60 in that it was easy, in theory at
least, to write custom microcode. I've heard that certain customized versions
of the 730 microcode were produced for special needs, and that DEC even
supported this with some development tools, but I've never seen any such thing
in the wild.
So, if anyway if anybody does find the sources or development tools for the
730/725 microcode, I'd love to see a copy.
Back to Bob's topic, I do have a running 730 system that could be powered on
more or less any time. I'm willing to run tests if anybody needs to experiment
with the behavior of real hardware. It's even on HECnet, so I could make
remote access available.
The 86x0 machines also have the microcode in RAM. It's all loaded from the FE
RL02 at start up. I have the documentation for all the microcode machines of
the 86x0, but I don't have the actual microcode sources, nor the tools used to
build the binaries.
That said, I guess it should be doable to disassemble the existing microcode if
one really wanted to.
The 11/60 was an interesting machine in that DEC actually provided the tools
for customers to write their own microcode.
The 11/750 had RAM to store patches to the microcode, but the basic version of
the microcode was in ROM.
Where did the 11/725 and 11/730 load their microcode from. Surely not the
TU58...
You nailed it. That pathetically slow tape drive was used to load the
microcode. I had an 11/730 at my first job 29 years ago and the wait to get the
bootstrap was interminable!
That is horrible. Even thinking of being absolutely dependent on a TU58
to even start the machine is bad. Not to mention slow...
Surprised as well, as they did it better on the 11/750 (I think), where
you don't need the TU58 for normal operation, but you still had the
ability to patch the microcode as needed.
Johnny
--
Johnny Billquist || "I'm on a bus
|| on a psychedelic trip
email: b...@softjar.se || Reading murder books
pdp is alive! || tryin' to stay hip" - B. Idol
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