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Conference decwet::ntaxp

Title:	Windows NT For Alpha AXP

Moderator:	TARKIN::LINEIBER

Created:	Mon Sep 27 1993
Last Modified:	Thu Jun 05 1997
Last Successful Update:	Fri Jun 06 1997
Number of topics:	1058
Total number of notes:	4567

1048.0. ">64KB read through SCSI?" by QUARK::LIONEL (Free advice is worth every cent) Tue May 13 1997 06:14

[I received the following in the mail today.  I'd be happy to forward any
answers to the customer.  Thanks - Steve]

Steve,
        Could you point me at someone who can answer the ultimate question?
I need to find out if The DEC Alpha can read data blocks
larger than 64K through a SCSI interface under WindowsNT. I have struck out
with my local DEC rep. and I am sure that someone at 
DEC knows the answer to this.
               Regards,

                 Ed Steele
                 Exploration Design Software
                 11191 Westheimer #214
                 Houston, Texas 77024

                 edsteele@phoenix.net

T.R	Title	User	Personal Name	Date	Lines
1048.1		QUARK::LIONEL	Free advice is worth every cent	`Wed May 21 1997 13:41`	3
	A stumper, eh? Is there somewhere else I should ask? Steve
1048.2	Here's an opinion ...	KERNEL::MEGARITY	I remember when Rock was young	`Thu May 22 1997 03:56`	23
	For this to be possible, both the following would have to be true :- o There would have to exist a native SCSI command that would do this. But, according to my non-current SCSI spec, both the READ LONG and READ(10) commands only allows 2 bytes for the transfer length, which means that the limit is 64K bytes. Of course, there might have been an improvement here or there might even be a vendor-specific SCSI command that would do this for certain disk drives. If it were me, I'd ask this question in ASK_SSAG. o There would have to exist a means within WIN32 of sending a native SCSI command to a disk drive - a bit like IO$_DIAGNOSE under OpenVMS. You could try the NT Developers conference for an answer to this question ... Hope this gets some discussion going ... /Ian
1048.3	check the OS conferences	WRKSYS::HOUSE	Kenny House, Workstations Engineering	`Thu May 22 1997 05:32`	20
	re .2 - allowed transfer length with SCSI commands ... READ(6) has one byte to count logical blocks (256512 -> 131,072 bytes) (00h means 256 blocks) READ(10) has two bytes to count logical blocks (65535512 -> 33,553,920 bytes) (0000h means 0 blocks) READ LONG has two bytes to count bytes Early SCSI chips we used had only a sixteen-bit byte counter (5380). Later chips had 24-bit (53C810) and 32-bit (1040B) counters. The actual transfer length limitaion is specific to each operating system. (I recall early versions of the OpenVMS SCSI drivers only allowed for 127-block transfers, maybe that's been increased in later versions.) -- Kenny House
1048.4	I stand corrected ...	KERNEL::MEGARITY	I remember when Rock was young	`Thu May 22 1997 05:41`	1