[mythtv-users] Build for dual HD recordings - also is PSU enough/too much

[Andre]

On 12 Mar 2011, at 09:02, Dan Smith wrote:

> On Fri, Mar 11, 2011 at 6:30 PM, Digital Hit Entertainment
> <dhenews at hotmail.com> wrote:
>> 
>> Looking to build a MythTV combined frontend/backend to ditch the cable and go with OTA HDTV. Want to be able to duplicate our current cable PVR which enables recording two HD programs while watching another recorded one.
>> 
>> How's this line up? Realize it's not an HTPC case, but it's a small tower and a good price.
>> Still need to find a good IR remote that works well with MythTV. Looking
>>  to buy in the next week or so.
>> 
>> 
>> I'm not 100% sure about whether the PSU is strong enough (or too much) so really need
>> input there. (one day it'd be great if sales sites had enough info
>> about components in their database to make PSU suggestions. :) )
>> 
>> 
>> Motherboard: Gigabyte GA-M68M-S2P mATX AM2+
>> 
>> CPU: AMD Athlon II X2 250 Dual Core Processor Socket AM3 3.0GHZ 2MB L2 Cache 65W Retail Box
>> 
>> Memory: G.SKILL F2-8500CL5D-4GBPK PC2-8500 4GB 2X2GB DDR2-1066 CL5-5-5-15 240PIN Dual Channel
>> 
>> HD: Western Digital WD Caviar Blue 1TB SATA 6GB/S 7200RPM 32MB Cache 3.5IN Hard Drive OEM
>> 
>> Case: Coolermaster Elite 342 Black M-ATX Mid Tower Case 2X5.25 5X3.5INT 1X3.5EXT No PSU
>> 
>> PSU: Corsair Builder Series CMPSU-430CX 430W ATX Power Supply Active PFC 120MM Fan
>> 
>> DVD: Liteon IHAS124 24X DVD Writer SATA Black OEM
>> 
>> Video: ASUS GeForce GT 430 700MHZ 1GB 1.6GHZ GDDR3 PCI-E DVI VGA HDMI Low Profile Video Card
>> 
>> TV Tuner: HD HOMERUN Dual Tuner
>> 
>> 
>> Thanks and have a great weekend.
>> 
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>> 
> 
> That 430W will be plenty, a 300W would be enough even, but you can't
> really have too big of a PSU.

Well unless you care about wasting power, very few PSU's are efficient at low loads, even the best 80+ PSU will not be 80% efficient at low load.

Fill out this form to get an estimate of the power you require:
http://extreme.outervision.com/psucalculatorlite.jsp

You want to have a healthy margin above what this suggests, 50% at least, 100% if you are planning big upgrades but if you are 200% or more over then efficiency will be very poor, many systems have PSUs that are rated at four or five time the actual requirement, of course many PSUs are not good for their rated power either!

There's nothing especially power hungry in the build so you may be wasting a lot of power (and therefore generating heat) with a 430W PSU, although it seems very difficult to buy a well made PSU around 400W never mind below, unless you can go down to <200W which I wouldn't recommend for this build.

If you are planning to add another seven disks and three more tuners then a bigger PSU may be worthwhile, the only other thing that justifies a big PSU is a gaming graphics card or worse several of them, the GT430 is very power efficient so that's not a concern.


> The PSU will only use the wattage the
> motherboard/components are pulling.

True but efficiency matters as most Myth boxes are on most if not all of the time.

The Corsair is a good PSU, I have several of theirs, runs cool, a 520W one is running 8 disks and 4 tuners in an i7 box, no hint of rail droop even when all 8 disks spin up simultaneously! Shame there's no spin up staging in a consumer bios.

I recently bought an Antec Earthwatts 380W, as being the smallest well designed efficient PSU I could find, runs an Atom server with 3 disks and the box is cold, not cool, cold so although I haven't measured efficiency I suspect it's quite good. I suspect a ~200W PSU would be even better but i couldn't find a compatible one in stock anywhere.


> The only things I worry about with
> a PSU is the efficiency and noise. HDHR Dual is the way to go for OTA,
> my single tuner (just starting out with OTA myself) is in the mail.
> The Dual tuner was well over twice as much from Newegg Canada, so just
> to see what I can get a single is good enough for now.
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