[mythtv-users] Apple TV info

[Scott D. Davilla]

>  > >    The AppleTV has a really crappy NIC chipset. It's sort of 
>like a winmodem.
>>  >Thus, if the CPU goes into some sort of power saving mode (that may be the
>>  >wrong term for it), then your network performance goes straight into the
>>  >crapper. You basically have to lock the CPU into "fully awake mode".
>>
>>  It's not the fault of the chipset, it's the Linux driver that can't
>>  deal with the CPU going into C3. Basically, the driver does not know
>>  about ACPI C1/C2/C3 power changes.
>
>     Why should that bother the NIC? Even if the CPU is stuck in ACPI
>state C3, the NIC performance shouldn't be total crap. That makes it
>sound like the "winmodem" remarks you see about that chipset on the
>web are pretty much on the mark.

Interrupt response time is much longer under C3 than C1/C2. If the 
driver was not written with the longer interrupt response time 
expected under C3, it will have overruns. I think the last time 
anyone touched this driver was several years ago before CPU power 
cycling was even done. There are some patches that change the buffer 
sizes if you really want to get to C3. Power wise on the AppleTV it 
just does not matter. Redefine it's powerstates from C1/C2/C3 to 
C1/C2 and don't worry about it.