[mythtv-users] performance on Via cpu when watching live tv

[Gareth Glaccum]

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In the meantime, could someone explain why watching live tv is more
intensive than watching pre-recorded shows? Because of the buffer kept
on hard disk? 

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When the system is recording a program, you can think of the following data flow

data is copied from the dvb card to pci-bus (either way, it is pci on your system) to main memory, myth acts on this data, and then copies it to disk, via a memory cache through the PCI bus again. 
When you watch the program, myth requests the data from the disk (which may or may not be gained from cache), then acts on it, and sends it to your graphics chip (AGP in your case I suspect). 

When you watch live tv, the above two steps are attempted at the same time.

There are three areas in your case where the juddering may be occuring due to hardware constraints. 
1) The hard disk itself, is it IDE/SATA, is it 5400 rpm or 7200, what size is the disk cache?
2) The PCI bus may be being overrun by all this data. I have a 2GHz jetway board, which has an issue with its pci bus in this way, I am having to be careful what the machine is doing. The previous revision of board, at 1.2GHz, does not have a PCI issue.
3) have you got the highest frequency, lowest latency memory you can get in your system. Unfortunately, VIA boards often only have 1 memory slot, so interleaving isn't possible, which makes memory choice a little more important.
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