Self modifying code, lambda calculus - Re: ENIAC programming

tony duell ard at
Fri Sep 18 23:51:00 CDT 2015

> The VAX-11/730 would have to have the microcode on TU58, as that is the
> console media. Quite possible that it actually do load the microcode
> from there at power up. I've heard that those machine were slow in so
> many ways... :-)

The 11/730 has no microcode ROM as far as I can see. However part of the
instruction decoding is done in hardware, so implementing a totally different
instruction set would be inefficient

The craziest thing I have found in the 11/730 is that the control store is 
dynamic RAM (lots of 16K*1 chips). Every few milliseconds the CPU is 
halted while the control store is refreshed. There is space for 4K more
of control store (1K of that is fitted if you have the integrated disk
controller or floating point board) which is SRAM. Quite why the whole
lot isn't SRAM is beyond me.


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