Transporting an LGP-30

Christian Corti cc at
Mon Dec 26 10:01:48 CST 2016

On Sat, 24 Dec 2016, william degnan wrote:
> Here are my notes on the LGP 30

There are several errors in those notes:

- "The basic (hardware) bootstrap in LGP-30 mnemonic format:"

There is no hardware bootstrap.

- The addresses in the bootstrap loader (program 9.0) must be hexadecimal 
and the bootstrap is entred as follows:

C3W00 - P0000
C3W04 - I0000
C3W08 - C3W14
C3W0J - P0000
C3W10 - I0000

- "4-character binary equivalent of the flexowriter single-character ascii 

Ehm, ASCII wasn't "invented" at that time. There are no Flexowriter 
commands, the Flexowriter code is the LGP-30 code.

- "First "B4627" is converted into binary-coded decimal format and entered 
into the accumulator"

There's no conversion, the character code of the Flexowriter *is* the 
binary code of the LGP-30.

- "The accumulator is actually 64 separate 32-bit accumulators (one for 
each drum track), same value on each copy."

The accumulator is one track with 32 double-width (i.e. 64 bits) sectors. 
You need the long accumulator when multiplying two 31-bit numbers (you 
can't store a 32 bit number to the memory because the LSB is always 0)
All the registers are circulating registers meaning that the contents is 
read and immediately written back to ensure that it is accessible at any 
word (sector) time.

Everything you need to know about the architecture and programming of the 
machine can be found in the manuals BTW (including schematics, flow 
charts, instruction description etc.). The manuals are online since many 
many years.


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