( ESNUG 383 Item 16 ) ------------------------------------------- [11/28/01]
Subject: ( ESNUG 380 #12 ) VCS Scales With Mhz While NC-Verilog Doesn't
> The following table lists the values reported back from the Unix "time"
> command on a couple of small synthesis jobs.
>
> job cpu Sun cpu Linux PC ratio
> 1 3059 sec 1715 sec 1.8x
> 2 652 347 1.9x
>
> Seems to track the MHz scale fairly nicely.
>
> - Scott Evans
> Sonics Inc. Mountain View, CA
From: [ To Infinity And Beyond ]
Hi, John,
Please keep me anonymous on this one. We run multiple sim environments
(different ASICs) on Linux / Solaris here, and use both Cadence NC-Verilog
and Chronologics VCS.
VCS:
----
I've also noticed that VCS gives a speedup which scales somewhat with the
MHz of the machine. My Linux VCS sims on a 1GHz PIII system with ( >1G of
memory) runs 50-70 % faster than on Solaris 400 MHz machines with similar
memory. That's great, because my Linux machines are a lot cheaper and
upgrading to faster boxes and larger memory is also easy. But I have found
if a VCS job starts swapping in and out of memory, the Solaris memory
subsystem seems to do a far better job than Linux. I try to make sure I
have enough memory to run a job on Linux (especially for gate level sims.)
VCS has a sparse memory model that reduces memory on some of my sims. It's
enabled with an embedded /*sparse*/ comment in your Verilog code. Its
undocumented, of course :-), so one needs to dig around. My AE told me to
use it as:
reg /*sparse*/ [31:0] pattern[0:100000000];
I've also noticed that processors with larger caches are better. I suppose
VCS has a high percentage of load-store instructions. I find that in
general VCS has better memory usage than NC-Verilog, so I can pack some more
sims into a multiprocessor machine, with relatively less memory.
NC-Verilog
----------
Has anyone seen that the ratio of performance improvement is not that much
on NC-Verilog on Linux vs. Solaris? (i.e. faster Mhz didn't speed up
NC-Verilog much.) I would like to see if others had similar experiences.
- [ To Infinity And Beyond ]
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