[mythtv-users] How much is too much CPU?

Warpme warpme at o2.pl
Mon Jun 3 20:40:57 UTC 2013


On 5/31/13 2:36 PM, Craig Treleaven wrote:
> I know, I know:  you can't be too rich or too thin or have too much 
> CPU, but...
>
> So my master backend/frontend machine is a 4 year old 1.83 Core 2 
> Duo.  It does OK but I'm really interested in http live streaming and 
> it clearly won't keep up with that.  I could see serving up to 3 HLS 
> clients in our house between iDevices and wireless laptops. I'd like 
> to buy something that will last another 4-6 years.
>
> Key loads on the machine:
> -master backend recording and commflagging 1080i/720p MPEG2 streams.
> -frontend
> -MythWeb server
> -HLS transcoding and serving (likely MythExpress)
> -household fileserver (backups and shared pictures, etc)
>
> The box could be commflagging two recordings, displaying another 
> program and transcoding up to three streams...and I'm sure 
> mythfilldatabase would kick off at the same time!
>
> So, how much CPU would all that need?  Could a Core i5 Dual keep up? 
> Core i7 Quad?
>
> I'd like to keep all these functions on one box because I don't have a 
> good spot to locate another box.  Also, I think one beefy box is 
> likely to cost less than two separate machines and chew up less 
> electricity.
>
> Appreciate any experience that others can offer.
>
> Craig
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> mythtv-users at mythtv.org
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>
Craig,

Just my experience regarding CPU:
Recently I decided to upgrade my BE from low power AMD platform (235e 
CPU; 880G chipset) to Intel platform (DH67BL; i3 3220T cpu).
BE is headless, has 6 tuners, 8G RAM and 10T storage (3x HDD)

1. power consumption (measured at wall):
idle 98..110 -> 68..77W
load 115..120 -> 80..85W
measured with 1600W-range kill-a-watt meter (so quantization errors on 
beg.scale ADC are giving probably high errors. In future I will measure 
power with ampero-meter (current) and look also with oscilloscope on PFC)

2. reschedules:
for approx 78 channels, 500+ scheduled items: 6.0...6.5s -> 2.9...3.5s

3. HLS transcode
AMD was able to keep real time with up to 1080i->360p
Intel gives me 1080->720p. 720p is OK; 768p is too much :-(

4.Myth compile (KVM on BE host vs VMware on OSX Desktop)
myth compile speed is comparable with my Desktop (quad Q6600 at 3.6G)

Generally I'm highly surprised by Intel advantage over AMD: for 25% less 
power it offers 3-5x more computing power (something like 2..2.5x from 
arch and next 1.5-2 times from HT).

I do upgrade as business case shows me it is worth: assuming I will sell 
on eBay my AMD Mobo/CPU with current prices (40-30% off) - overall power 
savings (measured at wall) will give break even after approx. 2,7y of 
24/7 operation.

Conclusions:
-With today's electricity prices swap to v.effective arch like 
Sandy/Ivy/Hasswell may make sense.
-i3 3220T (35W dual 2,8G IB with HT) can keep HLS up to 720p
-For general use, 35W IB CPU with stock clock is comparable with ~130W 
50% OC quad Kentsfield (Q6600)

I think You can consider SB/IB Intel chip.
Next Q is about Your requirements regarding HLS.
If 720p is enough - i3 3220T should be OK.
If You need more - then You should go for i5/i7.
In such case I will go for lower clocked i7 instead of higher clocked i5 
as i7 gives You HT. HT can greatly offset lower clock - however lower 
clock means lower TDP. As HT in Sandy/Ivy is totally different thing 
than in old "presshot" (look on my results with i3 with HT versus quad 
Q6600) - I strongly suggest i7 with clock like 1.8..2.2GHz.

Hope it helps!

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