peters@pulman.dec.com (Don Peters, APO-1/F8, 289-1242) (08/19/86)
There have been several comments regarding the speed of reading and
writing on the ST floppy drives. One person who has looked into the
problem and done something about it has commented on it within our
internal notes files here at Digital. He has been involved in the
development of Sedt (now in Beta test), a screen editor that is a
superset of the Digital supported EDT text editor.
Exerpts from his notes follow...
.
.
.
I have spent a lot of time trying to improve the speed
that Sedt loads and saves files at. By now it's getting pretty
decent. I did discover that the problems indeed are the ones
covered in the previous notes.
The first problem is that it's DEATH to use the higher
levels of C file routines in ALCYON C. Stream I/O runs
incredibly slow. I currently use the next lower level and will
migrate to the lowest (firmware).
The other problem is interleaving. I bought a SUPRA
20meg disk which they had mistakenly formatted with an interleave
factor of 2. Last weekend I reformatted it with 3 and saw a
marked improvement in speed. I guess that when you only get one
sector per revolution it really is slow. It must be the same
problem with the floppies.
.
.
.
By doing all the formatting myself and experimenting with
different transfer buffer sizes I was able to greatly improve the
floppy read/write times. Sedt now loads and saves files from
floppies between two and three times faster than Micro EMACS.
For any kind of read/write to or from floppies transfer rates
drop dramatically as the buffer length increases and then
flattens out around 6K buffers. After that is has a tendency to
go up and down a bit because of interleave delays. From this I
am 100% certain that the performance problems are caused by poor
interleaving of sectors on the floppy.
Anker
/Don Peters, Digital, 617-689-1242/
...decvax!decwrl!dec-rhea!dec-pulman!peters