RE: Unidentified subject!

[Dave New <NewD@esi.com>]

On an x86 architecture machine, the normal block
size can be as small as 4096 bytes (4K bytes), which
is the physical map page size in the processor tables.

This, of course, makes for potentially lots of small
blocks.  In practice, unless the memory is exceedingly
fragmented, you will hopefully see larger continguous
blocks.  The 'worst case', though, would be 4096 blocks
of 4096 bytes each, to transfer 16 MBytes.  A lot of
overhead in setting up all those transfers, unfortunately.

Cheers,

-- DaveN

-----Original Message-----
From: Jeff Leine [mailto:jeff.leine@lecroy.com]
Sent: Wednesday, November 15, 2000 9:48 AM
To: pci-sig@znyx.com
Subject: Unidentified subject!




Hello All,

Since the memory in a PC is not necessarily available in large blocks, it is
necessary to have a list of addresses and block lengths for a master to
write
to.  This is the scatter part of a scatter/gather DMA.

Is there any way I can determine how many of these blocks I have to support
if I
want to transfer 16 megabytes of data to memory?

Thank you in advance for you assistance,

Jeff