[mythtv-users] single core @ 65nm or dual core @ 90 nm?

[Brian Foddy]

On Sunday 13 May 2007 11:11 am, Steve Daniels wrote:
> Brian Foddy wrote:
> > On Sunday 13 May 2007 09:42 am, matt lutz wrote:
> >> I'm building a new HD frontend, and I'm trying to figure out which
> >> processor to buy.  I'm using a AM2 socket... The two choices seem to be
> >> between a dual-core 3800+ Windsor (90nm) at 2.0Ghz, or a single-core
> >> 3800+ Lima (65nm) at 2.4Ghz.  The 65nm will keep it a little cooler (and
> >> quieter).  Will it be enough to handle everything an HD frontend can
> >> throw at it?  It would seem that for a front-end only box, you wouldn't
> >> really need the dual-core.
> >>
> >> thanks for any advice you can give me.
> >>
> >> Matt
> >
> > I recently built a FE only machine for my parents using a X2-3800 EE
> > chip, still 65 watt like its 65nm  brother.  Runs very cool.  It will
> > play most HD content I tried at 50% speed (yes 1000Mhz), and when the
> > machine was idle, the stock cpu fan would frequently just turn off.  But
> > if you really need the power, it would crank up to full 2000Mhz and dual
> > core.  And not much diff cost wise.  Hard to beat.  I'll probably build
> > another for me soon.
> >
> > Brian
>
> Hi Brian,
>
> In Linux, how could you tell all of the above? (Apart from seeing the
> fan stop obviously..)
> What distro are you on and what tools do you use to get the info? Was
> any special config needed to get it working?
>
> Thanks
>
> Steve Daniels

There are CPU governor modules you can activate such as "conservative"
that will monitor the cpu load and if its lower than predefined numbers
will start dropping the core speed, on my cpu it was 2000, 1800, and 1000Mhz.
There are a few /proc files that will tell you the current speed.  The machine
I refer to, as I look at it right now, /proc/cpuinfo shows:
processor       : 1
vendor_id       : AuthenticAMD
cpu family      : 15
model           : 75
model name      : AMD Athlon(tm) 64 X2 Dual Core Processor 3800+
stepping        : 2
cpu MHz         : 1000.000

And lmsensors shows the fan speed at 780RPM right now.  It takes a bit
of getting used to watching a cpu load monitor like xosview showing 80%
load when the cpu is running at 50% speed, but that's what it does.
And the power usage drops accordingly also.  When the machine is maxed
out cpu load, my kill-a-watt meter shows it about 120 watts, at idle with
the cpu forced to full speed, it was about 75 watts, slow the cpu to 1/2 speed
at idle and it drops to under 60 watts; all without doing any power saving
on the harddrive.

Brian