I have finally upgraded my music computer. I started with an older P4 with
2.5G memory. It was working well and able to get good latency (sub ms by
qjackctl at 48000) but didn't have the guts to do much with it :) it had a
single core.
New MB: asus z87-k
CPU: intel i5 at 3.2G
I could have gotten an i7, but same speed/cores plus
hyperthreading. Hyperthreading is anti low latency. so
the i5 gives the same performance with less power use.
Memory: 8G, all one stick, which is slower than two 4G sticks...
maybe not the best choice, but seems ok.
Video: on board, dual monitors - VGA plus DVI both 1600x900
Disk: 2TB sata about 5 years old (as I recall)
Audio interface: Delta 66
Midi interface: ensoniq pci audio card.
I chose this MB because it had three pci slots as well as 4 pcie slots
which allowed me to keep using my old audio interfaces while giving me
possibilities for upgrades.
ASUS was nice enough to list the irq layout of the pci(e) slots in the
user guide. All three PCI slots are shared with something else :P
However, one is shared with a single channel PCIe slot - good! That PCIe
slot will not be used. That is where the delta 66 went. One is shared with
three PCIe slots and "IGD" (graphics?)... skip that one. The last is
shared with the SATA controller and that is where the ensoniq went. The
internal audio has its own irq (of course) but that is turned off in bios
(as useless). The USB setup uses 3 irqs (two for USB2 and one for USB3)
and so may do well with USB audio... if I had anything other than a USB1.1
audio device to try ;) I also turned the speed "Boost" off in bios as it
can not be controlled by the OS.
So far things look very good. With almost no changes at all and
3.13.0-24-lowlatency #46-Ubuntu for kernel (fresh ubuntustudio 64bit
14.04 install. I can run the D66 at 16 frames with very few xruns and all
are spurious. Just to be sure the ensoniq was not interfering I modified
the rtirq order to:
"rtc snd_ice1712 snd usb i8042"
This did make some small difference. Next, I turned cpufreq from ondemand
to userspace so I could play with different speeds. I set cpu0 to max
(3.2G) and assumed the others would follow all being on the same chip. I
was wrong and the other cores were actually at 800 Mhz (were ondemand had
left them). All of my xruns vanished. Ondemand sucks. I obviously wasn't
pushing this too hard (it would have been too hard on the old P4). I was
running jack at 16 frames (2 periods) with the pulse to jack bridge
running at the same time playing a video full screen too. Qjackctl said
the DSP load was less than 10% so I will have to find some way of loading
it up some more.
Things to try (to load the system):
- mostly MIDI stuff.
- keyboard in
- some HW synths I have around here
- soft synths... lots of them at once.
- IDJC with:
- live mic
- skype through pulse to idjc
- some mp3 or ogg files playing (at least two at once)
- maybe mumble at the same time too or more than one skype.
I will monitor the cpu temperature with different user set CPU speeds.
So far I am very happy with what I have seen. PCI is certainly not dead,
though it is getting harder to find. I could not find any Xeon boards with
PCI slots for example... even if I had wanted to pay the extra.
qjackctl gets loaded at session start and is setup to start jack and
a2jmidid when it runs. Pulse starts then too. Pulse is set up to have all
audio interfaces turned off so that jacksink/source is always default. For
all the bad things I have heard about pulseaudio... it just works.
--
Len Ovens
www.ovenwerks.net
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