Re: DMA from/to user-space memory

Thomas Sailer (
Mon, 25 May 1998 15:21:34 +0200

H. Peter Anvin wrote:

> For the moment, sound falls into this category. Fortunately, even
> sound is moving away from ISA, after having been stuck there for far
> beyond its time (due to the desire for compatibility with SoundBlaster
> backwardness.)

Yeah, and because we all like backwardness, Intel & Friends
devised what they call "DDMA" (Distributed DMA).
It's the obviously partly successful (S3 uses it) attempt to
make the already 20 years ago outdated 8237 concept work
with PCI.

In short, avoid S3 soundcards at all cost. You'll end up
trying to allocate sound DMA buffers below 16M even though this
is a PCI card. (The S3 manual documents an extension to DDMA
that apparently should allow DMA buffers anywhere in 32bit
address space, but I couldn't get it working although I tried
hard and S3 doesn't reply to tech queries.)


To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to