Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!iuvax!rutgers!apple!bloom-beacon!oberon!nunki.usc.edu!aliu
From: aliu@nunki.usc.edu (Alejandro Liu)
Newsgroups: comp.sys.cbm
Subject: Re: turbodisks
Summary: Faster Serial Communications for C-64 and 1541
Keywords: Faster Serial Communications for C-64 and 1541
Message-ID: <2719@nunki.usc.edu>
Date: 16 Feb 89 05:41:13 GMT
References: <8902130828.AA09474@MATH.Tau.Ac.IL>
Reply-To: aliu@nunki.usc.edu (Federal Bureau of Intelligence)
Organization: You must be kidding!
Lines: 25

One simple and unsophisticated (therefore, not that dramatic) approach
to the speed-up problem is by using the 1541 fast mode.  I remember
that the VIC-20 could make serial transfers 25% faster than the C-64,
that's why C-64's had such a hard time reading the old 1540 drives.
People who had VIC-20's could take advantage of this extra speed by
sending the user command 'uj' to the disk (I am not 100% percent sure
about this, I don't have my Disk Manual handy, but I think is fairly
common thing)
Anyway, a simple but easy way to speed up ALL disk operations is to
send this command to the disk drive, to put it at VIC-20 speed.  That
will make the 1541 run 25% faster.  Normally, the C-64 will have a
hard time coping with this extra speed.  The way to put the C-64 at
the same speed without great programming feast, is by simply blanking
the screen.  (Blanking the screen, produces the C-64 to run 25%
faster, because the Video Chip doesn't need to access the memory any
more).  Therefore, everytime one wants to perform a disk access, one
simply blanks the screen, and enjoy a humble 25% improvement in the
speed.  (I actually tested this on LOAD and SAVE, and works.  File
operations didn't improve at all because I was using BASIC, and
Commodore BASIC is slow enough that the Drive is still faster that the
interpreted BASIC)
-- 
 
                    aliu@nunki.usc.edu (Alejandro Liu) 
(Simple .signature, $CHEAP$)