Re: AW: general audio card Q

[Paul Davis <pbd@op.net>]

>Paul wrote:
>
>> cards that do not use DMA should generally be considered inferior
>> because of the extra CPU cycles they force on the host system.
>
>not generally. i.e. the pinnacle/fiji way is to map a piece of memory into
>the pc's memory space.
>thus an application using alsa-mmap can write (or read) directly into the
>cards pcm-memory.
>pretty efficiently, don't you think? (except that its ISA-memory)
>(it can do so with 2 or 3 periods per buffer).
>I don't see any drawback here caused by the lack of DMA.

yes, but this isn't what I mean by "a card that doesn't use
DMA". cards that don't use DMA require the host CPU to issue an
instruction per-small-piece-of-data to move it from host memory to the
interface memory. what you're describing is still instruction-free
movement of data between the two. the fact that the mapping is
interface->host rather than host->interface (as on the rme9652,
sblive, ice1712 and others) doesn't change that all that much.

--p


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