My colleague bought a Presonus FP10 firewire audio interface, which reports working nice in Linux. Moreover he owns a firewire controller made by Sunix with a Texas Instruments chipset. He tells us that for having jackd working without xrun and no other artifacts he needs to use 512 frame/periods, then latency is 34ms, which could be considered awful as this card is able to work with 2ms latency using other operating systems. He checked IRQ and saw that the firewire controller shared IRQ with the network interface. Check out output of lspci -v . 03:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168B PCI Express Gigabit Ethernet controller (rev 01) Subsystem: Giga-byte Technology Unknown device e000 Flags: bus master, fast devsel, latency 0, IRQ 17 I/O ports at a000 [size=256] Memory at eb000000 (64-bit, non-prefetchable) [size=4K] [virtual] Expansion ROM at 50000000 [disabled] [size=64K] Capabilities: <access denied> 04:01.0 FireWire (IEEE 1394): Texas Instruments TSB43AB23 IEEE-1394a-2000 Controller (PHY/Link) (prog-if 10 [OHCI]) Flags: bus master, medium devsel, latency 32, IRQ 17 Memory at ec004000 (32-bit, non-prefetchable) [size=2K] Memory at ec000000 (32-bit, non-prefetchable) [size=16K] Capabilities: <access denied> lspci lists 18 devices and every one of then reports 0 latency except the firewire controller. And hardware latency is 32ms, very near the 34ms of audio latency reported by jackd. So one could think that if the firewire controller added no latency, audio latency could be as low as 2ms. Strange, isn't it? So it looks that audio latency achievable by jackd is limited by hardware latency achievable by the firewire controller. He even tried locating a PCI slot that doesn't share IRQ and running the kernel with the noapic and nolapic options so the system ends reporting the sound card in the IRQ 11, which is nice. No change, hardware latency is 32ms in any case. marcel@ubuntu:~$ uname -a Linux ubuntu 2.6.22-14-rt #1 SMP PREEMPT RT Tue Feb 12 09:57:10 UTC 2008 i686 GNU/Linux Anything else can be tested? Or should he put back the PCI firewire controller and buy another? Which one? Any ideas welcome. Personal answers not to the list also welcome. Cordially, Ismael -- Ismael Valladolid Torres GnuPG key: DE721AF4 SHS Polar (3.4.3) Google Talk/Jabber/MSN Messenger: ivalladt@xxxxxxxxx C/ Emilio Vargas 1 Jaiku/Twitter/Skype/Yahoo!: ivalladt Edif. Fiteni II AIM/ICQ: 264472328 28043 Madrid (Spain) The opinions expressed here represent my own and not those of my employer. Las opiniones expresadas representan las mías propias y no las de mi empresa. _______________________________________________ Linux-audio-user mailing list Linux-audio-user@xxxxxxxxxxxxxxxxxxxx http://lists.linuxaudio.org/mailman/listinfo/linux-audio-user
