Path: utzoo!attcan!uunet!lll-winken!lll-tis!ames!pasteur!ucbvax!CORY.BERKELEY.EDU!dillon
From: dillon@CORY.BERKELEY.EDU (Matt Dillon)
Newsgroups: comp.sys.amiga.tech
Subject: Re: Having your cake (Re: Address Space on the Amiga (was Re: Need info on exceptions))
Message-ID: <8809021811.AA13386@cory.Berkeley.EDU>
Date: 2 Sep 88 18:11:25 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Lines: 14

:First thing to note... drivers already do a copy in the Amiga because (1)
:the system calls don't require block alignment, and (2) the driver uses the
:blitter to generate and decode MFM, so data outside MEMF_CHIP has to be copied
:anyway.

	No, copying is not required.  For instance, the FFS will pass along
data pointers to whichever trackdisk device it is mounted on whenever possible,
And MY microbotics StarDrive does NOT copy data to any buffers when reading/
writing but transfers it from the request to the SCSI bus directly.

	(In fact, everybody's mother except the floppy trackdisk device does
this).  That isn't to say copying is never used.... it is used quite a bit in
the OS, but it isn't used 100% of the time.

					-Matt