Changing hw.snd.pcm0.buffersize in 4.10.

Sandy Rutherford sandy at
Mon Dec 13 18:18:30 PST 2004

>>>>> On Mon, 13 Dec 2004 09:59:51 -0600, 
>>>>> Nikolas Britton <freebsd at> said:

 > In FreeBSD 5.3 you can change the buffersize by adding 
 > hint.pcm.0.buffersize="foo" to /boot/loader.conf, have you try'ed this 
 > with 4.x?

Yes.  Here are the contents of my /boot/loader.conf file:

[szamoca:6] cat /boot/loader.conf
# -- sysinstall generated deltas -- #


[szamoca:7] sysctl -a | grep snd
hw.snd.targetirqrate: 32
hw.snd.report_soft_formats: 1
hw.snd.verbose: 1
hw.snd.maxautovchans: 0
hw.snd.pcm0.buffersize: 4096
hw.snd.pcm0.vchans: 4

So it seems to have ignored the entry in loader.conf.  No errors or
warnings were generated during boot.  It just ignored the entry.

Also, here is my /dev/sndstat:

[szamoca:8] cat /dev/sndstat
FreeBSD Audio Driver (newpcm)
Installed devices:
pcm0: <SB16 DSP 4.02> at io 0x220 irq 5 drq 1:0 bufsz 4096d (1p/1r/4v channels duplex)


[szamoca:9] uname -a 
FreeBSD 4.10-RELEASE FreeBSD 4.10-RELEASE #35: Sat Sep 18 02:19:02 PDT 2004     root at  i386

 > Sandy Rutherford wrote:

 >> Is it possible to change the sysctl variable hw.snd.pcm0.buffersize
 >> (DMA buffer size for the soundcard) in FreeBSD 4.10?  I know that in
 >> 5.x this is changed in devices.hints.  I'm guessing that something in
 >> the kernel config file will do the job, but haven't been able to
 >> figure out what.
 >>  ....


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