[mythtv] Memory bandwith

[Calvin Harrigan]

On Fri, 2003-01-03 at 17:57, Bryce C wrote:
> I've found similar performance with an Athlon XP2000+ and 512Mb of PC133
> on a Soyo K7S5A.  I'll be trying some DDR memory wen I have a chance to
> pull some from another machine I have.
> 
> On Fri, 2003-01-03 at 15:37, Monty Walls wrote:
> > On Fri, 03 Jan 2003 21:56:37 +0100
> > Joel Larsson <joel@rosafluffmoln.nu> wrote:
> > 
> > > Im currently running myth on a AMD K7 650 mhz and that is a bit to slow 
> > > for livetv. Im investigating to purchase some new hardware. Anyway, the 
> > >       question is, do memory bandwith make any big differance?
> > > 
> > > I found these motherboards that have normal socket for SDRAM and support 
> > > for AMD XP 1700-2400 XP CPUs. Which is kinda good since I dont have to 
> > > buy new DDR memory for my machine. Or should I invest in a new 
> > > motherboard and DDR memory?
> > > 
> > 
> > My Athlon 1200 with a KT133 didn't have enought bandwidth on the PCI bus
> > (at least that's my guess) using pc133 memory for 640x480 rtjpeg+mp3.
> > 
> > 
<snip>

I wouldn't say that memory bandwidth doesn't make a difference, but I
think the problem may lay else where, processing power perhaps?

The PCI bandwith is theoretically 32bits(4bytes) x 33MHz or around
130MBs per/s.  640x480x16bits(yuv)x30fps = 18.MBs/s.  PCI should be able
to resonably handle the tv card even if it's only getting 75 percent of
it's maximum yield.  I currently use a XP1800 with 256 megs of PC133 on
an MSI kT133 board and it works quite well, not stuttering or any of the
sort.  I can watch live TV, record and playback simultaneously (outside
livetv) without a hiccup.

I should note that you might try increasing the PCI latency in the bios,
it helped me some in smoothing out my system.  It was not so much a
question of bandwidth, but more of bus contention, by increasing the
latency devices can hold the bus a bit longer to transfer data, or
somthing like that...  Getting forgetful in my old age.


Calvin...