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https://designers-guide.org/forum/YaBB.pl Simulators >> Circuit Simulators >> spectre on 64-bit linux vs 32-bit linux https://designers-guide.org/forum/YaBB.pl?num=1182389588 Message started by weelo on Jun 20th, 2007, 6:33pm |
Title: spectre on 64-bit linux vs 32-bit linux Post by weelo on Jun 20th, 2007, 6:33pm Does anyone have benchmark results for spectre on 32-bit rhel ws4 compared to its 64-bit cousin, on identical hardware of course. I have a couple systems running various flavors of ws4 as shown below, but none on identical hardware. I am wondering if it might be faster for typical spectre sims (few hundred to few thousand equations) if the machines were running 32b ws4 instead of 64b. fi0x:~> uname -a Linux fi0x 2.6.9-5.ELsmp #1 SMP Wed Jan 5 19:30:39 EST 2005 i686 i686 i386 GNU/Linux fi1x:~> uname -a Linux fi1x 2.6.9-5.ELsmp #1 SMP Wed Jan 5 19:29:47 EST 2005 x86_64 x86_64 x86_64 GNU/Linux |
Title: Re: spectre on 64-bit linux vs 32-bit linux Post by Bill Toole on Jun 22nd, 2007, 6:10am Hi I don't have any numbers but at one the companies i worked at we found very little difference in sim times in Cadence between 32 and 64 bit linux machines. Not sure if we had a 64 bit version of Cadence though. However there was a big difference with the 64 bit version of RFDE and GoldenGate when we had very large circuits. With the 32 bit version we were limited to about 2G of memory and it did not matter if you had more RAM so with large circuit we often could not even simulate them because we ran out of memory. With the 64 bit version we did not have this memory limitation (there still was a memory limitation but it was much larger and we did not hit it) and the sims could run so in this case we got huge speedup in our sim times. Does Cadence have a 64 bit version now? Bill |
Title: Re: spectre on 64-bit linux vs 32-bit linux Post by weelo on Jun 22nd, 2007, 10:50am Thanks for the info. As far as I can tell, spectre (mmsim61), ultrasim, and assura 316 all have 64bit versions of the tools, and these are the ones I care about the most. Typical sims I might run with spectre would be something like a simple block or behavioral model which I do a transient 2ms run on. It takes about 2 min on a P4 3.8GHz machine. The sim is scripted to run between 50 and 100 cases. For something like this, it's not a terribly big deal if 32b-spectre is slower than 64-b spectre. Circuit inventory: nodes 116 equations 196 ahdl simulator 1 va_ideal_clamp 3 va_ideal_clamp2 3 va_sr_latch 3 va_comparator 3 capacitor 15 cccs 6 diode 15 inductor 3 mos1 12 quantity 9 relay 9 resistor 27 vccs 6 vcvs 6 vsource 47 However, for mid-level or top-level simulations and extracted sims, using spectreVerilog, the netlist looks like: Circuit inventory: nodes 4318 equations 13684 a2d 36 bsim3v3 3999 capacitor 2355 d2a 53 diode 928 inductor 2 isource 2 quantity 9 resistor 1911 vbic 28 vsource 650 Something like this takes between 10hrs and >40hrs for a 1ms transient run on the same machine. The actual time depends on various modes of the circuit and its dynamic behavior during certain intervals of the simulation. I am looking for any possible way to shorten these 40hr runs to something more reasonable. The machine is not in danger of running out of memory for these sims, so if 32b spectre could be any faster, I'd retool my fast box for 32b linux instead. |
Title: Re: spectre on 64-bit linux vs 32-bit linux Post by Geoffrey_Coram on Jun 25th, 2007, 5:36am I would expect 64bit executables to be slightly slower because the data structures are twice as big. But I wouldn't expect it to be more than a 5% difference. |
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