Any own an 11/725...?

[Lee Courtney]

> IIRC the Burroughs computers would load a different instruction set  
> depending on what language was being used.

B1700

Lee Courtney


> -----Original Message-----
> From: cctalk-bounces at classiccmp.org
> [mailto:cctalk-bounces at classiccmp.org]On Behalf Of CRC
> Sent: Monday, October 24, 2005 8:40 AM
> To: cctalk at classiccmp.org
> Subject: Re: Any own an 11/725...?
> 
> 
> 
> On Mon, 24 Oct 2005 05:00:57 +0100 (BST), ard at p850ug1.demon.co.uk  
> (Tony Duell) wrote:
> 
> >
> >>> The 11/730, of course, is mostly PALs (as I said) with some RAM as a
> >>> control store, 8 off 2901s as the ALU, and an 8085 (I think) to  
> >>> load the
> >>> control store, etc. One day I am going to look into modifying the
> >>> microcode of that machine...
> >>>
> >>
> >> To what end?  Increased performance?
> >>
> >
> > NO, just for fun... I doubt very much I could improve on the  
> > performance
> > for running the VAX instruction set. I have not looked at the prints
> > carefully enough to determine how much of the instruction set is
> > hard-wired (if any), I wonder if it would be possible to run a  
> > different
> > instruction set entirely.
> >
> > -tony
> >
> >
> 
> Actually, with access to the micro instructions you can often  
> substantially improve the run-time of a given program. The Modcomp II  
> had the microbus accessible for use along with a number of unused  
> instructions. The communications instructions and floating point were  
> implemented using this bus.
> 
> I implemented an instruction store attached to this bus and which  
> allowed me to create and store new instructions. A friend working on  
> a CS Phd in pattern matching ginned up a program that would find  
> common instruction sequences in a program, deconstruct the microcode,  
> perform optimization on the sequence and then create a new  
> instruction which was substituted for the original sequence. We often  
> got increases of performance of 20% over the original code.
> 
> IIRC the Burroughs computers would load a different instruction set  
> depending on what language was being used. Tony could create a VAX  
> with Forth as the instruction set ;-)
> 
>      CRC