audio chip properties

[Jan Stary]

Hello,

in an attempt to fully understand my SoundBlaster AEW64 card, running
on FreeBSD 5.4-RELEASE-p6, I have the following question: after
kldloading snd_sbc and snd_sb16, I get

# kldload snd_sbc
sbc0: <Creative SB AWE64> at port 0x388-0x38b,0x330-0x331,0x220-0x22f irq 5 drq
 5,1 on isa0

# kldload snd_sb16
pcm0: <SB16 DSP 4.16> on sbc0

$ cat /dev/sndstat
FreeBSD Audio Driver (newpcm)
Installed devices:
pcm0: <SB16 DSP 4.16> at io 0x220 irq 5 drq 1:5 bufsz 4096d kld snd_sb16 (1p/1r/1v channels duplex default)

I wonder what exactly do the fields mean; please correct me
where I am wrong: it seems to me that

a) a SB16 DSP 4.16 audio chip was found
b) at address 0x220

c) it wants to send its interrupts via irq channel 5
   and the kernel agrees to that.

d) the "DMA channel number" (man device.hints) is 1 or 5?
   What exactly does "drq 1:5" mean? Is this the "secondary
   DMA channel" which man snd_sbc speaks about? If so, what is
   "secondary" about it, ie what is the "primary DMA channel"?

e) the DMA buffer is 4096 bytes; what does the "d" stand for?

f) the device is driven by the snd_sb16 module

g) it has one playback channel, one record channel, and one virtual
   channel; it is capable of full duplex (ie, can playback and record
   at the same time); it is the default audio device.


	Thanks for any hints

		Jan