[mythtv-users] Killer system or overkill?

Len Reed crunchyfrog at charter.net
Tue Dec 13 16:39:58 EST 2005

Raphael Pooser wrote:

> As people here have said, your system is pretty much right on for an 
> HDTV set up that could say, transcode at the same time as watching live 
> TV for instance.  For just watching straight live TV or HDTV recordings, 
> as someone else said any fairly recent athlon64 variant (like a 3200+ as 
> you were thinking) would do.  As to the question about more RAM, true 
> that in linux the ram you give it the more it can use and the more stuff 
> you can have open, unlike in windows with most of its applications.  
> However, if I was going to choose between one more gig of ram or going 
> from one to dual core, dual core would definitely win out.  Mainly the 
> only performance increase you are gonna get is in the RAID (from the 
> benchmarks quoted in above post), but since you don't need anything 
> anywhere nearly close to that level of performance as you already knew, 
> the extra 1GB or RAM is pretty much wasting money.  I don't know how I 
> could possibly get mythtv to actually fill up a gig of RAM at any rate.  
> Maybe a backend connected to 5 or so frontends?
> Raphael

Thanks.  Your response (and others) matches what I'd expected to hear: 
dual core if I want to do something else CPU-intensive (like transcode) 
as well as run myth.  I still don't see -- as you obviously don't -- how 
an extra GB of RAM will improve things much.  I'd have to be doing 
something else on the system that did heavy I/O or otherwise could use a 
lot of RAM.  Capture of data from an HD card gets data at a very flat 
rate:  either you keep up or you don't.  Basic queueing theory shows 
that if the arrival rate is near constant you won't get a big queue (for 
disk output).  Consequently, beyond the minimum amount of buffering 
needed to keep up and a bit of headroom for safety, a huge buffer cache 
will just hold things that aren't going to be read back any time soon 
any way.  The benchmark referred to was for a different kind of load on 
the RAID system.


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