Path: utzoo!utgpu!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!rutgers!ucsd!ucbvax!hoptoad!tim
From: tim@hoptoad.uucp (Tim Maroney)
Newsgroups: comp.sys.mac.programmer
Subject: Re: VBLS are OK above BufPtr
Message-ID: <6142@hoptoad.uucp>
Date: 1 Jan 89 20:59:16 GMT
References: <10606@umn-cs.CS.UMN.EDU>
Reply-To: tim@hoptoad.UUCP (Tim Maroney)
Organization: Eclectic Software, San Francisco
Lines: 20

In article <10606@umn-cs.CS.UMN.EDU> imp@crayview.msi.umn.edu (Chuck
Lukaszewski) writes:
>I am loathe to believe that the VBL Task Handler has a special test that
>permits VBLs below BufPtr and above ROMBase.  Not only does it seem pointless
>to create a VBL desert anywhere in memory, but also the instruction waste
>would be ludicrous, even for Apple :-).  So it seems safe to say that
>VBLs are safe above BufPtr.  Anyone from Apple care to comment?

Probably not, but I will.  The situation I referred to was in the 64K (pre-
Mac-Plus) ROM, and was fixed in the 128K (Mac Plus) ROM.  It is of interest
only to those who wish to be compatible with the old ROMs.

>It also occurs to me that I have seen _VInstall and _VRemove in the .MPP or
>.ATP driver, which are also in ROM.

This is true in the 128K ROM, but not in the 64K ROM.
-- 
Tim Maroney, Consultant, Eclectic Software, sun!hoptoad!tim
"If you vote for clowns, you have no right to complain that only clowns
 make it to the ballot." -- Tim Maroney