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From: ewhac@well.UUCP
Newsgroups: comp.sys.amiga
Subject: Re: The LIVE Digitizer from A-Squared and the 68020
Message-ID: <3216@well.UUCP>
Date: Wed, 3-Jun-87 19:30:32 EDT
Article-I.D.: well.3216
Posted: Wed Jun  3 19:30:32 1987
Date-Received: Sat, 6-Jun-87 06:10:35 EDT
References: <8705290639.AA04316@ingres.Berkeley.EDU> <4419@videovax.Tek.COM>
Reply-To: ewhac@well.UUCP (Leo 'Bols Ewhac' Schwab)
Organization: Whole Earth 'Lectronic Link, Sausalito, CA
Lines: 31
Summary: You can too use a 68020

In article <4419@videovax.Tek.COM> stever@videovax.Tek.COM (Steven E. Rice, P.E.) writes:
>In article <8705290639.AA04316@ingres.Berkeley.EDU>, Doug Merritt
>(hatcher@INGRES.BERKELEY.EDU) writes:
>
>> . . . The thing [LIVE]
>> has to use self-modifying code just to implement *menus*...that's about
>> as bandwidth limited as you get! (Note that this prevents its use on a
>> 68020, since the cache on a 68020 prevents self-modifying code.)
>               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>
>Nope!  If you want to do such things on a 68020, just clear the Enable
>bit in the Cache Control Register.  [ ... ]
>
	You don't need to do this.  The LIVE software uses 20 MOVE.W
instructions per line to copy data to the frame buffer.  There are 200 lines
in a display, which means 4000 move instructions.  I don't think anyone's
cache is that big.

	The self-modifying aspect of the LIVE code alters the appropriate
sections of the code to map out a "hole" in the bitmap that menus and
requestors can be rendered into.  Thus, all menus and requestors are exact
multiples of 16 pixels wide (!).

	Assuming I understand the operation of LIVE correctly, you should be
able to use it with your 68020.

_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_
Leo L. Schwab -- The Guy in The Cape	ihnp4!ptsfa -\
 \_ -_	 Bike shrunk by popular demand,	      dual ---> !{well,unicom}!ewhac
O----^o	 But it's still the only way to fly.  hplabs / (pronounced "AE-wack")
"Work FOR?  I don't work FOR anybody!  I'm just having fun."  -- The Doctor