[rescue] VAXstation questions

Dave McGuire mcguire at neurotica.com
Tue May 13 18:02:35 CDT 2003

On Tuesday, May 13, 2003, at 06:32 PM, Frank Van Damme wrote:
> I suspected something like that... Now if you could comment on the 
> memory
> usage a bit :-)

   Oh, that's a fun one.  First of all, they're very forgiving about 
object alignment in memory...much less memory is "wasted" in general, 
relative to some other architectures.  Alpha comes to mind...In very 
basic terms, Alphas trade off memory utilization efficiency for memory 
access performance.

   The second (and probably biggest) thing is the fact that the VAX 
architecture is the very epitome of CISC.  Single instructions that 
perform operations which would take dozens of instructions on a modern 
RISC architecture.  You're no doubt familiar with Cyclic Redundancy 
Check...CRC.  It takes about half a page of C code to implement a CRC.  
The VAX has a CRC *instruction*.  This greater instruction "potency" 
(for lack of a better term) means it takes far fewer bytes of machine 
code to perform the same work.

   Here is a real-world example of this, again drawing a comparison 
between VAX and Alpha architectures, using this trivial C program:

#include <stdio.h>
void main(void)
   printf("hello world\n");

   On an Alpha running NetBSD, observe the compiled and stripped binary:

snagglepuss$ ls -l helloworld
-rwxr-xr-x  1 mcguire  wheel  6640 May 13 18:57 helloworld*
snagglepuss$ size helloworld
text    data    bss     dec     hex     filename
3479    580     80      4139    102b    helloworld

   ...while on a VAX, also running NetBSD, built from an identical 
source file:

vlc$ ls -l helloworld
-rwxr-xr-x  1 mcguire  wheel  3816 May 13 18:57 helloworld
vlc$ size helloworld
text    data    bss     dec     hex     filename
1844    260     40      2144    860     helloworld

   Get it?


Dave McGuire                "Why would a brothel need
St. Petersburg, FL            a streaming media server?"      -Kevin

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