Path: utzoo!utgpu!attcan!uunet!lll-winken!lll-tis!helios.ee.lbl.gov!ace.ee.lbl.gov!leres
From: leres@ace.ee.lbl.gov (Craig Leres)
Newsgroups: comp.unix.wizards
Subject: Re: Sun 4's and DR11-W
Message-ID: <585@helios.ee.lbl.gov>
Date: 2 Aug 88 21:41:09 GMT
References: <1069@ucsd.EDU>
Sender: usenet@helios.ee.lbl.gov
Reply-To: leres@helios.ee.lbl.gov (Craig Leres)
Organization: Lawrence Berkeley Laboratory, Berkeley
Lines: 11

This is probably unrelated to Jim Hutchison's DR11 problem, but is of
interest to people porting device drivers from the 68K to sparc
families. When dealing with 16 bit data vme address space (16d16,
24d16, 32d16), you're supposed to only do 16 bit accesses.

If you do a 32 bit access in 16 bit data vme address space on the
68020, the processor (or memory management) automatically does two 16
accesses. But the hardware on a sparc isn't so helpful; so if you need
to read a 32 bit register (for example) you've got to do the 16 bit
reads and construct the 32 bit quanity yourself.

		Craig