"D from BC" <m...@comic.com> wrote in message 
news:p...@4ax.com...
> I did spot the max treads option under the LTspice control panel.
> It's set to 2.
> I haven't noticed a change in speed. :(

That's because with hyperthreaded CPUs, "50% utilization" of "one CPU" is 
still using (nearly) 100% of the total clock cycles available if nothing else 
is running on the "second" CPU.

In other words... you get 1 billion operations per second (or whatever). 
Hyperthreaded CPUs just give the appearance of two CPUs so that if a 
particular thread is waiting on, e.g., a memory read from DRAM (this can take 
hundreds of cycles), another thread can run in those hundreds of cycles. 
However, if the thread is never waiting on anything, it will consume all 1 
billion cycles every second.

A 1GHz hyperthreaded CPU can compute pi no faster than a non-hyperthreaded 
CPU.  (Nor will it be any slow.)  But hyperthreaded is a win when you have 
multiple *different* threads running around when one starts having to wait and 
would otherwise just be wasting CPU cycles...

"linnix" <m...@linnix.info-for.us> wrote in message 
news:4...@x16g2000prn.googlegroups.com...
>> I wonder if the other SPICE program writers are massively pissed about
>> LTspice being free.
> Not any more than than original free spice.  I just downloaded the
> source, compiled and spiced.

Oh, I think they're a little more ticked than before -- LTspice has many, many 
improvements over Berkeley SPICE, plus it has a decent (if simplistic) 
integrated graphing/probing environment, that had to be provided by various 
(not as tightly-integrated) add-ons with the Berkeley SPICE.

"Jim Thompson" <T...@My-Web-Site.com> wrote in 
message news:7...@4ax.com...
> No.  Engineers don't choose simulators, jerks in management do...

And amazingly, sometimes those jerks haven't even used SPICE in years (since, 
e.g., college)... and possibly not ever!

On Tue, 20 Jan 2009 22:13:38 +0000, Nobody <n...@nowhere.com> wrote:

>On Tue, 20 Jan 2009 11:44:07 -0800, D from BC wrote:
>
>> I have an old single core puter using hyperthreading with XP.
>> 
>> If I got this right..
>> XP thinks it's got 2 CPU's. 
>> One thread will only use 50% of CPU mips.
>> So when I run spice, the CPU is only 1/2 working.
>> The other half is for whatever...email,browser,OS stuff etc.
>
>With hyperthreading, a single thread will use the entire CPU in the
>absence of any competing threads (Windows reports that it's only 50%, but
>it's lying; you can confirm this by running two processes on an
>otherwise-idle system and noting that one process runs more slowly as the
>other process consumes more CPU).

So maybe I have LTspice running at nearly full blast with my single
core yet 2 virtual core ye old hyperthreading Pentium 4 Prescott.

>
>If you have a CPU with two full cores (Pentium-M), the only way that you
>can utilise both cores is with multi-threaded code. You can't make the CPU
>behave as a single, faster core.



D from BC
myrealaddress(at)comic(dot)com
British Columbia
Canada

"D from BC" <m...@comic.com> wrote in message 
news:p...@4ax.com...
> On Tue, 20 Jan 2009 13:06:51 -0800, D from BC
> <m...@comic.com> wrote:
>
>>On Tue, 20 Jan 2009 21:13:44 +0100, "Helmut Sennewald"
>><h...@t-online.de> wrote:
>>
>>>"D from BC" <m...@comic.com> schrieb im Newsbeitrag
>>>news:d...@4ax.com...
>>>>I have an old single core puter using hyperthreading with XP.
>>>>
>>>> If I got this right..
>>>> XP thinks it's got 2 CPU's.
>>>> One thread will only use 50% of CPU mips.
>>>> So when I run spice, the CPU is only 1/2 working.
>>>> The other half is for whatever...email,browser,OS stuff etc.
>>>>
>>>> I want spice to at full speed.
>>>> Is there a way to set XP such that only my spice app gets nearly 
>>>> full
>>>> CPU attention?
>>>> When the spice app is not running, the computer goes back to 50 50
>>>> hyperthreading.
>>>>
>>>> Note: I do have the option in bios to disengage hyperthreading.
>>>> I might do that if hyperthreading is being a pita.
>>>>
>>>>
>>>> D from BC
>>>> myrealaddress(at)comic(dot)com
>>>> British Columbia
>>>> Canada
>>>
>>>
>>>Hello,
>>>
>>>You can get what you asked for if you use the latest LTspiceIV.
>>>It will stress all your CPU-cores to its limits. Let's see when the 
>>>first
>>>people will claim LTspice has burned their Quadcore-CPUs because
>>>of  running long lasting simulation runs. :-)
>>>
>>>None of  the other SPICE programs you can afford will use more
>>>than one CPU-core.
>>>
>>>Best regards,
>>>Helmut
>>>
>>
>>Great!
>>
>>I checked my LTspice version ..it's version 2.25d :( Ugh..
>>I'll get version 4.
>>
>>Thanks
>>
>>
>>D from BC
>>myrealaddress(at)comic(dot)com
>>British Columbia
>>Canada
>
> I'm running LTspice4 now. Confirmed using help/about.
> However. in Windows task manager scad3.exe is running.. huh...
>
> Anyways..
> My spice is not running faster and Windows Task Manager is only
> showing CPU usage at 50%. iow...1 virtual core saturated.
>
> I did spot the max treads option under the LTspice control panel.
> It's set to 2.
>
> I haven't noticed a change in speed. :(
>
>

Try to disable Hyperthreading in the BIOS. In rare cases it will 
actually slow things down, like in SQL server

Cheers
 

On Tue, 20 Jan 2009 11:44:07 -0800, D from BC
<m...@comic.com> wrote:

>I have an old single core puter using hyperthreading with XP.
>
>If I got this right..
>XP thinks it's got 2 CPU's. 
>One thread will only use 50% of CPU mips.
>So when I run spice, the CPU is only 1/2 working.
>The other half is for whatever...email,browser,OS stuff etc.
>
>I want spice to at full speed.
>Is there a way to set XP such that only my spice app gets nearly full
>CPU attention?
>When the spice app is not running, the computer goes back to 50 50
>hyperthreading.
>
>Note: I do have the option in bios to disengage hyperthreading.
>I might do that if hyperthreading is being a pita.
>
>
>D from BC
>myrealaddress(at)comic(dot)com
>British Columbia
>Canada

After reading replies, I did this experiment..

Ran the simulation and looked at the simulation run speed at the
bottom of the LTspice window.

LTspice reports simulation speed ~27us/s 
Windows shows a total CPU usage at 50%

Spawned another instance of LTspice and run the same simulation at the
same time..

LTspice reports simulation speed ~15us/s 
Windows shows 100% CPU usage..

2 threads, one core, so the hyperthreading splits up the work.

1 thread one core, the hyperthreading lets the thread use up all the
mips as long as there's no completing threads.

Thanks for replies...That clears that up.


D from BC
myrealaddress(at)comic(dot)com
British Columbia
Canada

> No.  Engineers don't choose simulators, jerks in management do...
> that's why Cadence sales are so high, even though, IMNSHO, it's a
> royal piece-a-crap, grossly user unfriendly and butt slow.
>
> [snip]
>

As the kids say: THIS.
So much THIS.

"Helmut Sennewald" <h...@t-online.de> writes:

> "D from BC" <m...@comic.com> schrieb im Newsbeitrag 
> news:d...@4ax.com...
>>I have an old single core puter using hyperthreading with XP.
>>
>> If I got this right..
>> XP thinks it's got 2 CPU's.
>> One thread will only use 50% of CPU mips.
>> So when I run spice, the CPU is only 1/2 working.
>> The other half is for whatever...email,browser,OS stuff etc.
>>
>> I want spice to at full speed.
>> Is there a way to set XP such that only my spice app gets nearly full
>> CPU attention?
>> When the spice app is not running, the computer goes back to 50 50
>> hyperthreading.
>>
>> Note: I do have the option in bios to disengage hyperthreading.
>> I might do that if hyperthreading is being a pita.
>>
>>
>> D from BC
>> myrealaddress(at)comic(dot)com
>> British Columbia
>> Canada
>
>
> Hello,
>
> You can get what you asked for if you use the latest LTspiceIV.
> It will stress all your CPU-cores to its limits. Let's see when the first
> people will claim LTspice has burned their Quadcore-CPUs because
> of  running long lasting simulation runs. :-)
>
> None of  the other SPICE programs you can afford will use more
> than one CPU-core.


None of my other *programs* use more than one CPU core (that I have
noticed).

And that's using Wine on linux! It was the first time I ever saw
"400%" CPU usage. Good job Mike.

-- 

John Devereux

D from BC <m...@comic.com> wrote:

>
>I wonder if the other SPICE program writers are massively pissed about
>LTspice being free.
>

I don't think so. Ltspice is not very user friendly IMHO.

-- 
Failure does not prove something is impossible, failure simply
indicates you are not using the right tools...
                     "If it doesn't fit, use a bigger hammer!"
--------------------------------------------------------------

"Nico Coesel" <n...@puntnl.niks> wrote in message 
news:4...@news.planet.nl...
> I don't think so. Ltspice is not very user friendly IMHO.

Compared to entering netlists by hand it's quite friendly. :-)