FW: [Simh] SimH vax.exe cpu usage on Windows.

Wed May 19 10:12:14 EDT 2004

>>
>> Since your system is NOT a Notebook (which could benefit from
>> dynamically turning down clock speed when the system is idle to
>> reduce battery power consumption), running the CPU at 100% won't hurt
>> anything.  It won't create more heat, or make your disks work harder,
>> or anything.
>>
>
>Is this correct ?  My understanding is that the CPU heat is directly related
>to how much work the CPU is actually doing.  I quick monitoring of my own
>CPU temperature seems to reveal an increased temperature when the CPU is
>blocked at 100% busy.
>
>The overclocker guys are obsessive about this fact.  I have also seen
>suggested that CPU life expectancy is directly related to thelong term
>thermal load under which it is placed - cooler being better.
>
>I may be wrong on all counts, but I think Bishops concern is that he may
>decrease the life expectancy of his CPU by always having SIMH running, due
>to greater than normal thermal loads.
>
>Unless it is overclocked (and probably not even then) I do not think this
>should be a problem.

$0.02 to throw in regarding running CPU's at 100% for extended periods of time.
Yes, CPU temperature is directly related to the amount of load placed on the CPU, but only to a certain extent; it usually maxes out at a bearable point, especially if you have a decent cooler attached.  Additional heat can be generated (typically this is something only over-clockers worry about) by increasing some of the voltage levels in the BIOS, but that's only really necessary for over-clocking.
As far as system longevity being affected by continual use: I run my own PC-scale server at home and leave it on 24/7.  The CPU that was in the system (just previous to the current one) was in the system, powered and at 100% usage (thanks to http://www.distributed.net/) for approximately 3 years.  And the chip still runs like a champ!
On a side note, you can throw together a PC system that's more than capable of handling simh for just a couple $100; or, heck, get a cheap, old system at a trade show or Micro Center.
$0.02

> Andreas suggested that if you could figure out when the simulated
> system is "idle", you could get the simulator to idle itself as well.
>  As I've already said this is likely not worth the effort since there
> really is no net gain.
>
> There is, however, one case where implementing such an "idle"ing
> concept would benefit things.  This would come up if you somehow
> wanted or needed to run more than one simulator on the same host
> system simultaneously.
>
> All of that said, I've actually have a version of simh VAX which does
> support idling (or yielding) the CPU when the simulated system is
> idling.  The changes to support this affect several chinks of simh
> code.  I submitted it to Bob about a year and a half ago, and he
> didn't see the need.
>

Personally though, I would have included these changes, unless they have
some massive downside.

philip lewis

> - Mark Pizzolato
>
> --- "Bishop, Lewis" <lewis.bishop at eds.com> wrote:
>> Thanks for the responses so far...
>>
>> I have a dilemma whereby I cannot really justify a separate system
>> as this
>> is a home setup and whilst it's nice to have up and running it
>> won't
>> honestly get much use. The performance of the system itself is
>> actually
>> okay, however, at times with the load on the system it does affect
>> it quite
>> a bit - the system is also functioning as a PDC and exchange server
>> and runs
>> virtual SuSE Linux and Solaris systems with Oracle installed in
>> each - so it
>> does a fair bit! ;-) Memory is not a problem as it has 1gb -
>> normally
>> leaving 256mb (25%) free after everything else.
>>
>> I'm keen to reduce the CPU as I don't like to run the CPU at 100%
>> for long.
>> I'm not convinced it's good for it, especially as it's not a server
>> grade
>> system (i.e. it's a beefed up home PC or it was when I bought it 4
>> years
>> ago!).  There are a number of discussions around discussing this
>> type of
>> usage and a lot of concerns are raised not so much over the high
>> CPU usage
>> but over the other system components that have to run - i.e.
>> cooling fans,
>> power supply etc... all of these components, having a limited
>> lifetime are
>> going to fail at some stage - running a fan 24/7 is obviously going
>> to
>> stress it more than a few hours running per day.
>>
>> I have set the priority down to low and to be honest it doesn't
>> seem to make
>> any difference to the overall system performance. I've tried some
>> of the PC
>> slow utilities but these have not reduced the CPU usage (didn't
>> think they
>> would). If it cannot be done within SimH then maybe some form of
>> resource
>> manager would  be good?
>>
>> Anyone have any further ideas?
>>
>> Lewis Bishop
>>
>>
>> -----Original Message-----
>> From: Parker, David [mailto:David.Parker at stjohn.org]
>> Sent: Tuesday, 18 May 2004 4:29 p.m.
>> To: Bishop, Lewis
>> Subject: RE: [Simh] SimH vax.exe cpu usage on Windows.
>>
>>
>> You could try setting the priority lower on the application
>> process.
>> Or, if performance is just that important, run it on another
>> machine.
>> I'm running mine (pretty much the same setup) on an old 850Mhz CPU
>> and it's
>> decent.
>>
>> $0.02
>>
>> -----Original Message-----
>> From: Bishop, Lewis [mailto:lewis.bishop at eds.com]
>> Sent: Mon 5/17/2004 6:20 PM
>> To: 'simh at trailing-edge.com'
>> Cc:
>> Subject: [Simh] SimH vax.exe cpu usage on Windows.
>>
>>
>>
>> Hi all,
>>
>> I have OpemVMS 7.3 running under SimH v2.10-3 under Windows 2000
>> with the
>> networking option using WinPCap and a 2nd NIC. I'm really happy
>> with
>> the
>> fact that i can get VMS running on a windows machine (after not
>> using it for
>> 6 years or so) but i'm a bit concerned to see the cpu usage by
>> vax.exe
>> sitting at max (as much as it can get) and taking complete system
>> cpu to
>> 100%.
>>
>> Although system performance is not 'hammered' by this (it releases
>> resource
>> when requested) the system performance has suffered slightly. I
>> have
>> tested
>> the latest distribution (v3.2) but it is the same - does anyone
>> know
>> if
>> there is a way to limit the CPU usage for vax.exe?
>>
>> Thanks,
>>
>> Lewis Bishop.
>>
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