Self modifying code, lambda calculus - Re: ENIAC programming

Johnny Billquist bqt at
Fri Sep 18 16:33:20 CDT 2015

On 2015-09-18 15:33, tony duell wrote:
>>> Are there any computers that do let you put microcode into RAM
>>> now-days.
>> "Now-days"?  There are some that do that, some of which are still in
>> operational shape.  Some VAXen, in particular, have something called
>> "writable control store", which is essentially microcode RAM.
> As far as I know, the VAX11/730 (There is one next to me waiting for me to have time
> to restore it) has the microcode entirely in RAM. Classic PERQs (3 in the next room) have
> their microcode entirely in RAM too (in that case, there is a microcode boot ROM to load
> the microcode from disk, but it is switched out after the microcode is loaded).

While we're listing things, the VAX-86x0 have the microcode in ram. It 
is loaded from an RL02 at power up, by the PDP-11 front end.


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