[Info-vax] Bliss was Re: Learning VMS application programming

[Johnny Billquist]

On 2014-09-08 16:21, Bob Koehler wrote:
> In article <lujtpg$4p4$1 at Iltempo.Update.UU.SE>, Johnny Billquist <bqt at softjar.se> writes:
>>
>> I wish I could get my hands on that experiment. I think that today it
>> would be possible to get a native BLISS compiler running under RSX, and
>> with reasonable capacity.
>
>     I'd not be so sure.  Overlays may add more flexibility to the
>     address space, but they also add overhead, which uses up address
>     space.  Memory resident overlays are faster than disk resident
>     overlays, but they still add overhead.

They used overlays in their attempt to get it running. As the paper 
mention, it worked, but the problem was that it could not deal with the 
size of the input modules.

Things have changed significantly since then. RSX-11M-PLUS supports 
split I/D-space, which means you can get a lot more memory to have data 
in. You also have supervisor mode libraries, which moves a whole bunch 
of common code out from you address space.

Which means you can do things with much less overlays today, and still 
get much more use out. So, the uBLISS compiler DEC did on RSX back then, 
would probably not be too hard to get working today, and with lots more 
memory for the compiler to use for compilation instead of its own code.

	Johnny