SIMH LGP-30 Progress.

Christian Corti cc at
Wed Feb 11 05:03:17 CST 2015

On Wed, 11 Feb 2015, B Degnan wrote:
> via trial and error, and a lot of reading.  I believe that loading the
> bootstrap manually is a must; one cannot use or create tapes otherwise.

Only if your drum memory loses its contents. I don't know if SIMH has a 
concept of non-volatile main storage (drum, core). And for the LGP-30, all 
registers are non-volatile, too.

> think this SIMH has the bootstrap pre-loaded.  I am unaware of anyone who
> is using the SIMH simulator, although I have seen two non-SIMH LGP-30
> simulators.  One is in German.

That's mine, but there's an English version, too.

> In order to enter instructions into memory I first learned how to translate
> code from the various actual papertape sources, for example...
> "flexowriter entry"> 6300 P 0000'
> becomes
> sim> d -a 6300 10000000

Urks, that's sick... but SIMH should offer the possibility to enter the 
mnemonics and addresses (or anything else since everything is mapped to 
its four bit code) like
sim> d -a 3w00 p0000     (or d -a 6300 p0000
sim> d -a 3w04 i0000         d -a 6301 i0000 ...)
sim> d -a 3w08 c3w14
sim> d -a 3w0j p0000
sim> d -a 3w10 i0000
sim> g 3w00

Anyways, SIMH is not very well suited for machines like an LGP-30 where 
the user interaction with typewriter and console buttons for operation is 
imperative. The SIMH version does officially work, but it is not really 
user friendly in this case.
But the best would be if you use a drum image with 10.4 (the monitor) 
already loaded, i.e. save the memory contents to a file and reload it on 
the next incarnation of SIMH (there's a "START" drum containing 10.4 in my 
simulator package, and an "ACT5" drum with preloaded ACT-V and 
subroutines, these may be usable in SIMH, but I don't know).

> repertoire.  The hardest part is finding ways to enter Flexowriter key
> input via a modern keyboard, using SIMH commands.

By using a simulator that offers the right frontend to the user (i.e. keys 
and buttons as required by the machine operations) *g*


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