[LAU] 16 frames, no xruns -> Mobo + CPU + RAM + PSU < 180,- €

Ralf Mardorf ralf.mardorf at alice-dsl.net
Tue Feb 21 23:13:32 UTC 2017


Hi,

if you should need a cheap computer for audio, the setup I'm using
might be interesting for you, too.

RME HDSPe AIO                    48 KHz, 32 frames, no xruns
Focusrite Scarlett 18i20 2nd Gen 48 KHz, 16 frames, no xruns

Another advantage, the PC is absolutely silent, but there are also two
disadvantages. There are issues with the Intel graphics and the PSU
cables already smelled bad, when it wasn't used.

For compiling in tmpfs I'll get 4 additional GiB of RAM soon or
later, since 4 GiB aren't enough to compile a kernel. However, compiling
a kernel using a SSD instead of tmpfs takes 60 minutes.

Even with the shared IRQs there are no xruns, at least not for
a test song I already used with my old mobo and the Focusrite. On the
9 years old mobo the RME AIO at 256 frames run with inaudible xruns
and the Focusrite at 128 frames without xruns, so the test song already
says a little bit about the audio performance of the new mobo.

I didn't check MIDI jitter and a test is just a test, but seemingly
this cheap computer is usable for audio.

Some IRQs differ after a reboot, but the RME card, the TerraTec card
and ehci always share IRQ 16.

[root at archlinux rocketmouse]# hwinfo --bios | grep Manufacturer -A1 | head -2; hwinfo --cpu | grep Model | sort -u; hwinfo --memory | grep Size
    Manufacturer: "Gigabyte Technology Co., Ltd."
    Product: "B85M-D3H"
  Model: 6.60.3 "Intel(R) Celeron(R) CPU G1840 @ 2.80GHz"
  Memory Size: 3 GB + 768 MB
[root at archlinux rocketmouse]# cat /sys/devices/system/cpu/cpu*/cpufreq/scaling_governorperformance
performance
[root at archlinux rocketmouse]# aplay -l | grep -v HDA\ Intel | grep -v Sub
**** List of PLAYBACK Hardware Devices ****
card 0: HDSPMx579bcc [RME AIO_579bcc], device 0: RME AIO [RME AIO]
card 1: EWX2496 [TerraTec EWX24/96], device 0: ICE1712 multi [ICE1712 multi]
card 5: USB [Scarlett 18i20 USB], device 0: USB Audio [USB Audio]
[root at archlinux rocketmouse]# uname -rm
4.9.11-rt9-1-rt-celeron x86_64
[root at archlinux rocketmouse]# rtirq status

  PID CLS RTPRIO  NI PRI %CPU STAT COMMAND	
  102 FF      90   - 130  0.3 S    irq/16-ehci_hcd	
  105 FF      90   - 130  0.1 S    irq/25-xhci_hcd	
  121 FF      89   - 129  0.0 S    irq/23-ehci_hcd	
  257 FF      85   - 125  0.4 S    irq/16-snd_hdsp	
  373 FF      80   - 120  0.0 S    irq/16-snd_ice1	
   38 FF      50   -  90  0.0 S    irq/9-acpi	
   52 FF      50   -  90  0.0 S    irq/8-rtc0	
  103 FF      50   -  90  0.0 S    irq/1-i8042	
  106 FF      50   -  90  0.0 S    irq/26-ahci[000	
  256 FF      50   -  90  0.0 S    irq/27-mei_me	
  258 FF      50   -  90  0.0 S    irq/5-parport0	
  260 FF      50   -  90  0.0 S    irq/28-snd_hda_	
  262 FF      50   -  90  0.0 S    irq/29-i915	
  374 FF      50   -  90  0.0 S    irq/18-i801_smb	
  375 FF      50   -  90  0.0 S    irq/31-snd_hda_	
  485 FF      50   -  90  0.0 S    irq/30-enp3s0	
    3 TS       -   0  19  0.0 S    ksoftirqd/0	
   21 TS       -   0  19  0.0 S    ksoftirqd/1

The BIOS is used with it's defaults and I didn't update the BIOS. Since
everything seems to be ok for audio, I'll only disable the onboard
sound and the full screen logo, but won't upgrade the BIOS or change
any serious settings.

Regards,
Ralf


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