[mythtv-users] Re: Draft revisions to HowTo section 3.3, second try

[Dr. J. S. Pezaris]

> 3.3.2 Memory
> 
> A MythTV host that is both a backend and a frontend, and that uses 
> software encoding with a single capture card, should run comfortably in 
> 256 MB of RAM; depending on other hardware choices, even less (128 MB) 
> might suffice. Any common type of RAM in use today is fast enough. 
> Additional RAM is useful, but it mainly serves as buffer space to smooth 
> the process of sync'ing to the hard disk. For that reason, a swap 
> partition is effectively useless.

My experience relates directly to this issue.  I have experimented with two
different motherboards (Via VA6 and Shuttle FV25) two different processors
(PIII 700 MHz and Celeron 1.4 GHz), two different sets of memory SIMMs
(PC100 and PC133), and various clock speeds.  While processor speed is
certainly a factor, the primary factor in MythTV performance is memory
access speed.  By "MythTV performance" I mean the maximum resolution and
quality readily achievable with a given codec for recording only.

For example, the same motherboard (VA6) with the same memory SIMMs (PC100
and also PC133) performed nearly identically with a PIII-700 and
Celeron-1.4 on MythTV.

The same processor (Celeron-1.4) on the same motherboard (VA6 and also
FV25) with different SIMMs (PC100 vs PC133, with memory clock speed
adjusted accordingly) had a dramatic effect on MythTV performance.

In overclocking mode, tweaking the processor clock speed did not have
nearly the effect that tweaking the memory clock speed did.

This all makes sense: video applications typically have high miss rates at
the cache and are thus memory bound.

The conclusion: faster memory systems will work better.  If you can, avoid
PC100 memory and systems.  Similarily, if you can, use DDR memory systems.

Does anyone have a set up with other motherboards (eg, Via EPIA) who can
perform similar tests between memory speeds?  Or a motherboard which
supports PC133 as well as DDR?

	- pz.