[linux-dvb] How might a SATA drive interfere with DVB-S

Jon Burgess jburgess at uklinux.net
Mon Feb 20 23:42:28 CET 2006


Reinhard Nissl wrote:
> Hi,
> Attached you'll find my lspci -vv. Interrupts seem to be different, but 
> is a latency of 0 ok for the SATA device?
> 
> ------------------------------------------------------------------------
> 
> 00:1f.2 IDE interface: Intel Corporation 82801EB (ICH5) SATA Controller (rev 02) (prog-if 8a [Master SecP PriP])
> 	Subsystem: Fujitsu Siemens Computer GmbH: Unknown device 101c
> 	Control: I/O+ Mem- BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B-
> 	Status: Cap- 66MHz+ UDF- FastB2B+ ParErr- DEVSEL=medium >TAbort- <TAbort- <MAbort- >SERR- <PERR-
> 	Latency: 0
> 	Interrupt: pin A routed to IRQ 169
> 	Region 0: I/O ports at <unassigned>
> 	Region 1: I/O ports at <unassigned>
> 	Region 2: I/O ports at <unassigned>
> 	Region 3: I/O ports at <unassigned>
> 	Region 4: I/O ports at 2c00 [size=16]
> 

Since this controller is integrated into the ICH SouthBridge chip 
instead of being on a discrete PCI bus I'm not sure if the latency 
figure makes any difference. I had a quick look at a machine with an 
'845 chipset and that had similar 0 latency values.

I think however that some of the settings the above indicate that you're 
running in legacy/combined mode rather than using the native sata_piix 
driver. Does the disk appear as /dev/sdX or /dev/hdX? If using the 
libata drivers it should appear as /dev/sdX.

If not, try going into the BIOS and try to find a SATA setting referred 
to as Native/Enhanced (it may currently be set to something like 
legacy/combined).

I've seen one machine where using the legacy mode resulted in a 
performance of around 1MB/s at 99% CPU utilisation. Switching to the 
enhanced mode got the performance up to a much more normal 40MB/s @ ~20% 
CPU.

	Jon




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