Acquiring a bunch of Lisp Machines

Brad Parker brad at
Sun Sep 27 07:49:03 CDT 2015

On 9/25/15 9:20 PM, Guy Sotomayor wrote:
> Some work has been done to build an emulator but it was based upon 
> trying to emulate the code
> that ran on the Alpha.  No one to my knowledge has created an emulator 
> for the 36xx series
> machines.
It's good to see that the MFM emulator worked on a 3640.  I bought one 
and planned to try that experiment
at some point.  The SCSI emulator (scsi2sd) works well on the scsi based 
xl1200's and I have cloned a few
disks.  I have a working 3640 with a booting MFM disk which I 
should/will clone once I find the pcb (which is currently hiding)

It's true about the disks - the bad block info - at least on the large 
SMD and RLL lists was written at the factory once and that was it.  But 
if you had a "perfect disk" (for example one that was emulated), you 
could recreate a FEP file structure from scratch and if you had a 
distribution tape you should be able to load the needed files onto it.  
I suspect you could do all of that "outboard", i.e. using a linux 
computer into a disk image.  The FEP file structure and LMFS file system 
are not that complex. And if you could take a MFM signal image and turn 
it back into 1280 byte blocks, then you'd have a good example to 
decompose and compare with (since that now exits).

Heck, worst case you could do it from the FEP itself - but I think you'd 
need a dc-300 drive emulator and a image of a distribution tape.  That 
should not be hard - the carts exists and I can't imagine a tape 
interface being that hard to emulate.

I think the MFM format, even with it's odd block size is known and 
reasonable;  But the FEP loading code is obscure. (I've never seen FEP 
source code despite searching for a long time) But the format of the 
disk is pretty well documented in the lisp code and is known.

I made a feeble attempt at a 3600 macro code interpreter at one point.  
More just for fun than anything else.  I based it on the microcode in 
the patent application but it only got so far.  I think documentation 
did exist, but I'm not sure it's ever seen the light of day.  I've never 
seen any.  The holy grail would be a source copy of the latest microcode 
with all the support files.  It has to be on a magtape somewhere in 
someone's basement...

There is documentation for later ivory based machines (xl1200, etc...); 
the macro code and other important information has surfaced and is 
available.  The emulator has gone through various incarnations and 
improvements but remains (sadly) private.  I heard the latest version 
was completely rewritten in modern C.

I still hope some day someone will cough up some tapes with internal 
files on the 3600.  It should be possible to make an emulator or at the 
very least run the microcode.  There are schematics on the web. I have 
(briefly) considered putting them in an FPGA but fortunately came to my 
senses.  I think if I had the FEP source code I'd get motivated again 
because I've yet to figure out the format of the microcode binaries 
(which would be essential if one wanted to actually run the 3600 
hardware engine in simulation).  It might be one of those "be careful 
what you wish for" statements :-)  I still remember Al sending me the 
binary images of the CADR boot proms.

I think that 3620 is VLSI based.  There have to CAD files somewhere 
which describe the logic.


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