🚀 go-pugleaf

In article <1992Nov5.113540.1@uwovax.uwo.ca>, brent@uwovax.uwo.ca (Brent Sterner) writes...
> 
>   Just curious about memory demands for alpha.  I'm running a VAX 4500
>with 128 MB memory.  Of that, SHO MEM tells me "38393 pages are permanently
>allocated to VMS".  How big is VMS on an alpha system?  
> [text deleted]

In general, code expansion from VAX to Alpha is typical for RISC processors:
perhaps 1.8 to 1:  but there is wide variation.  As mentioned in a previous
note, compiler techniques such as inlining, loop unrolling, etc all increase
the size of the program text to improve performance.

Data expansion from VAX to Alpha should be negligible, unless the program
contains a lot of packed and unaligned data which gets properly aligned
during recompilation.  Note that the decision to align data or leave it
unaligned is controllable at compile time, but aligned data produces much
better performance.

As for VMS itself, several factors are at work.  Some of VMS requirements
are not in bytes but in pages.  For example, the minimum process needs
a certain number of pages for stack, stack guard, etc;  these were 512 bytes
on a VAX but are 8192 bytes on an Alpha.  In addition, to improve performance,
VMS on Alpha allows (under user control) the entire operating system to be
loaded resident, without paging.  Consequently, the minimum memory requirement
for Alpha VMS systems is currently 32MB, and that much or more is included
in the minimum configuration for all announced systems.

Bob Supnik	>Supnik@human.enet.dec.com
		>All opinions expressed are those of a hardline microcoder
		>and do not reflect those of Digital Equipment Corporation