Newsgroups: comp.arch
Path: utzoo!utgpu!watserv1!sunee!gpsteffl
From: gpsteffl@sunee.waterloo.edu (Glenn Patrick Steffler)
Subject: Re: Hardware mice pointers
Message-ID: <1990Jun18.002343.17567@sunee.waterloo.edu>
Organization: Gerbils On Speed Inc.
References: <136288@sun.Eng.Sun.COM> <6537@vax1.acs.udel.EDU> <11876@cbmvax.commodore.com> <2264@crdos1.crd.ge.COM> <WAYNE.90Jun14082016@ds <1308@nyx.UUCP> <1990Jun16.142023.19048@ux1.cso.uiuc.edu>
Date: Mon, 18 Jun 90 00:23:43 GMT
Lines: 47

In article <1990Jun16.142023.19048@ux1.cso.uiuc.edu> mcdonald@aries.scs.uiuc.edu (Doug McDonald) writes:
>For a hardware mouse pointer to work generally, doesn't the hardware have
>to have enough mouse pointer memory to allow storage of all the possible
>mouse pointers the user may want? Any given program might need three or

Mouse pointer storage could simply be some area of memory refered to by
the hardware, which then displays the pointer without CPU intervention. If
the pointers shape requires changing, simply re-map the address of the
pointer bit map to the suitable design.

The Amiga, and FM-Towns are two modern examples of sprite (read
hardware cursor) technology done in that manner.  The v7VGA board from
Video Seven (for IBM PCs) supplies a single hardware cursor.  I am not
sure how it maps its sprite memory.

>four in addition to the system-wide ones. And this memory has to be 
>writable by a program. So you might need say 32 mouse pointers. And some
>mechanism to change from one to another as it moves over various windows.
>How many screen systems have the necessary automatic mechanism to change
>mouse pointers as it moves?

That sounds like a brain dead way of implementing the cursor...the
proper vantage point with which to view this is not to minimize memory
bandwidth by having the sprites memory separate from the video, but
that the CPU is not performing the masked copies and transfers required
to implement the cursor in a non-hardware controlled cursor scheme.

>As I move the mouse around my present screen I count nine different 
>mouse pointers. And I'm only running three programs.

Thats not so much...the Amiga allows the hardware cursor to take up as
many forms as can fit in 512k,1Mb,2Mb (pick your model) of video
memory.  Large amounts of semi-dedicated video memory, and hardware
sprites have their advantages.  (but hey, lets not get into a fight in
alt. religion. computers ) :-)


>Doug McDonald


Lo-ha,

-- 
Co-Op    _____           "Bo doesn't know software" - George Brett
Scum   _/|__Q_\___ 
U of   | ww--+----#\    "Catch the mystery catch the spit!" - Tom Saywer (Rush)
Loo'91 ~~()~~~~~()~~                                     Glenn Patrick Steffler
