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From: rhyde@musial.ucr.edu (randy hyde)
Newsgroups: comp.sys.apple2
Subject: Re: speed loss
Message-ID: <13842@ucrmath.ucr.edu>
Date: 24 Apr 91 16:43:59 GMT
References: <9104181535.AA28525@apple.com> <1991Apr20.080839.27678@ux1.cso.uiuc.edu> <1991Apr23.170359.19679@nevada.edu>
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Reply-To: rhyde@musial.ucr.edu (randy hyde)
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>>>>>
I can't speak for other systems, but the Apple II doesn't need these
utilities since processor time isn't eaten up for memory refresh.
<<<<<

True, but the Apple II (this does not apply to the GS) only runs at 1
Mhz and needs memory which is twice as fast as the processor.  The
refresh (and video display) use the memory half the time and the
processor the other half.  This worked fine in the days when memory was
twice as fast as the processor.  Today, the reverse is true.  Indeed,
processors are many times faster than cheap memory.
A 17 Mhz 65816 requires outrageously fast RAM.  To get the invisible
refresh it would need twice as outrageously fast RAM (something like
5ns).  Since no one can afford a large stockpile of this stuff, I feel
the *small* percentage of overhead required for refresh is reasonable. 
BTW, as processors get faster, the percentage of overhead associated
with refresh goes down (of course, memory has to get faster too...).