[linux-dvb] How might a SATA drive interfere with DVB-S
jburgess at uklinux.net
Mon Feb 20 21:05:45 CET 2006
William Smith wrote:
> I have an Asus mobo with a Sempron 2400. I don't think this has
> Cool & Quiet. These two mobos I have had were among the very
> first with S-ATA.
Most boards with early SATA support used an extra chip sat on the PCI
bus to provide the SATA ports (often a Silicon Image 3112). The regular
IDE ports OTOH were normally integrated in the North Bridge part which
avoids contention with the PCI peripherals.
The bandwidth achievable by SATA with a modern hard disk is in the order
of 50MB/s which takes a significant proportion of the theoretical
maximum PCI bandwidth of 133MB/s (for a 32bit/33MHz PCI bus) and can hog
the PCI bus at the expense of other peripherals.
You should make sure that you are using the libata SATA drivers in
native mode which will appear as /dev/sdX (not /dev/hdX which happens if
you use the combined or legacy modes in the BIOS).
In addition to increasing the buffer sizes as suggested by Johannes, you
could try tweaking the PCI bus latency parameters. Use lspci to identify
the <bus:slot.function> of your SATA controller and then:
# setpci -s 02:0b.0 latency_timer=20
where 02:0b.0 is the location of the chip, 20 (in hex) sets a latency of
32. A lower latency timer reduces the time that this chip can hold the
bus once another device requests access. Conversely you could increase
the latency timer for the DVB card.
Be warned though, tweaking at this level is really a black art and can
cause problems (e.g. might cause your SATA controller to start
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