Path: utzoo!attcan!uunet!lll-winken!csd4.milw.wisc.edu!bionet!agate!ucbvax!amethyst.bucknell.EDU!hentosh
From: hentosh@amethyst.bucknell.EDU
Newsgroups: comp.sys.apple
Subject: Re: Hard drive speed
Message-ID: <8904141716.AA26507@amethyst>
Date: 14 Apr 89 17:16:57 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 26

>The bottleneck of the Apple ][ line is I/O. All reads and writes to the slots
>and to the video are made at 1 MHz. The Inner Drive gets around this by basing
>
>jeremy mereness

The way I understand it is that only *writes* to *video* will cause a slow
down to 1MHz. Reads from video *do not*.  Both writes and reads to the *I/O*
spaces ($C000-CFFF) cause the processor to slow down. But access the the ROM,
where firmware is located, doesn't cause a decrease in speed (in fact it runs
faster than a program in fast ram since it doesn't have to slow down for
refresh (refresh cuases an 8% decrese in speed)). The engineers did a good
job! (the clock runs at 2.8MHz) Too bad another video buffer wasn't added or
better yet a hardware memory move for the entire shadowed (well at least video
) area when switching to shadowed access.

This brings me back to a queston asked awhile ago on the net, but got no
response.  If you access slow ram from native mode. The FPI syncs up with
the MEGA II, well for how long does it stay synced for one operation,
for part of an operation or for more than one operation so that it won't
have to sync up for consecutive calls. Any IIgs engineers out there?

Bob

-- InterNet: hentosh@amethyst.bucknell.edu | 'Ever have deja vu and amnesia
   BITNET  : hentoshr@bknlvms.bitnet       |  at the same time?'
   AppleLink PE : RobertH128               |            -- Steve Wright