[Coco] Re: POKEd floppy access
flexser at fiu.edu
Wed Apr 26 15:29:17 EDT 2006
You're thinking of cassette, where tapes written at double speed can only
(without special techniques) be read at that speed. Disk I/O works fine
if you save at high speed and read at low speed, if the ROM has been patched for
On Wed, 26 Apr 2006 farna at att.net wrote:
> IIRC ADOS would "fix" the double speed drive access "problem". I ALSO seem
> to recall that if you write a disk at double speed, you can read it ONLY AT
> DOUBLE SPEED. Try slowing the CoCo back to normal speed and reading a disk
> you wrote at double. I bet it won't! The only problem is you have to
> remember to speed up to read those disks.
> When I wrote a genealogy program for the CoCo 3 (needed the wide display
> screen) it was pretty fast because I used every trick I could find --
> including double speed. But for disk I/O there was a line to slow it back
> down before and a line to speed back up after. The disks may have been fine
> at double speed, but would have been unreadable if someone wanted to use the
> data in another program unless they knew to speed the computer up. I
> definitely wanted the disks to be as reliable as possible for data storage
> though, especially since the records were prewritten to the disk, not formed
> as they were created. That's another trick that made the program pretty fast
> for a data base -- it just filled in blanks that were already there (a
> "create data format" program formatted the data disk). The drawback to this
> method was if a sector went bad i corrupted the disk up to the bad sector.
> Anything written beyond would be lost. People were encouraged to make
> regular backups.
> -- Frank Swygert Publisher, "American Independent Magazine" (AIM) For all
> AMC enthusiasts http://farna.home.att.net/AIM.html (free download
> -------------- Original message ----------------------
> > Date: Tue, 25 Apr 2006 19:30:26 -0400
> > From: Diego Barizo <diegoba at adinet.com.uy>
> > Subject: Re: [Coco] POKEd floppy access
> > Just regular "RS-DOS".
> > Could be that changing the step rate of the drives has any effect in
> > this area?
> > Diego
> > Robert Gault wrote:
> > > Just depends on the values in certain timing loops in DOS. Some third
> > > party DOS were written to handle disk I/O at 2MHz. What DOS are you
> > > running?
> > >
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