SBP 1394 hard drives hang with Windows XP (rare)

Peter Johansson PJohansson at
Fri May 2 10:16:54 PDT 2003

* From the T10 Reflector (t10 at, posted by:
* Peter Johansson <PJohansson at>
At 07:48 AM 5/2/2003 -0700, Mike Berhan wrote:

>Is it an I/O larger than 64K that has an issue?  128K?  256K?  Some 
>scatter/gather limitation?

Mike, since I don't know the internals of Microsoft's SBP driver, this is 
mere speculation---but it COULD be a software problem. Given a 512-byte 
logical block size, the largest data transfer that may be made WITHOUT 
recourse to a page table is 65,024 bytes (just a block shy of 64 KiB). Of 
course, arbitrarily large data transfers maybe described by using a page 
table. But if the data is contiguous in memory and wouldn't otherwise 
require a page table, perhaps there's a loophole in the driver?

As I said, this is just speculation on my part. I hope you get a more 
useful answer from Microsoft or some of the bridge chip vendors.


Peter Johansson

Congruent Software, Inc.
98 Colorado Avenue
Berkeley, CA  94707

(510) 527-3926
(510) 527-3856 FAX

PJohansson at

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