Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!rutgers!apple!bionet!agate!ucbvax!CORY.BERKELEY.EDU!dillon
From: dillon@CORY.BERKELEY.EDU (Matt Dillon)
Newsgroups: comp.sys.amiga
Subject: Re: A HD controller review
Message-ID: <8810260216.AA00223@cory.Berkeley.EDU>
Date: 26 Oct 88 02:16:13 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Lines: 27

:BufMemType = 1
:BTW, if someone could enlighten me about the purpose of the "BufMemType" entry,
:I'd much appreciate it. I have tried both 1 and 0, and each time the buffers
:are allocated from FastMem, which of course is the right thing to do, I guess,
:but then what the heck is this BufMemType entry for?

	Exactly what it says .. the type of memory that can be used in
buffers passed to the trackdisk. 

	MEMF_PUBLIC	1
	MEMF_CHIP	2    MEMF_CHIP|MEMF_PUBLIC = 3
	MEMF_FAST	4    MEMF_FAST|MEMF_PUBLIC = 5
	any memory: 1 (just MEMF_PUBLIC).
		
	It depends on the kind of driver you have.  Some drivers,
like the floppy trackdisk.device, can only utilize CHIP memory and
thus BufMemType = 3 (MEMF_PUBLIC|MEMF_CHIP).  0 is private and 1 is
public, and since neither CHIP or FAST is specified, both can be used if
you specify 0 or 1.  (Side note: Theoretically, you should always specify
MEMF_PUBLIC and thus should never specify 0).

	Some add-on 32 bit memory cards (not the C-A one) cannot be DMA'd
to and implement another memory type, MEMF_DMA or something like that
which must be specified in the BufMemType so the filesystem allocates only
DMAable memory for sector buffers.

				-Matt