16 Mar
2000
16 Mar
'00
4:16 a.m.
--- Philip.Belben(a)powertech.co.uk wrote:
> The "serial" bus is actually a
bastardised implementation of the IEEE-488
> bus, which CBM had used on the PET series.
Caused, IIRC, by Tramiel who demanded of the engineers that the next computer
not use the same connectors because of a supplier shortage at some point in
the PET's past (dunno if it was the edge-connector end or the IEEE-488 end
that was hard to come by, but that's the story that's been circulating for
twenty years).
> Data is transferred serially (at 300 baud)
instead of in parallel, other
> than that I believe it's pretty much IEEE.
It is, effectively, the same character protocol, but the serial bus is
lacking in some of the handshaking lines that characterized the true IEEE-488.
There's a great book on the PET and its implementation of the IEEE-488 bus
by Osborne Press. If you ever see a copy of it at a bookstore or flea market
and have even considered programming for the PET, grab it.
Are you _sure_ it's 300 baud? I thought it was
2400. We had a 20K byte load
module that took about a minute to load - this corresponds to a little over
300 _bytes_ per second. Same load module from tape took SEVEN minutes! No
wonder speed loaders and things were popular! (Typical disk speed loader
used 2 of the wires in the serial bus for data, doubling the throughput. May
have used higher baud rate as well
It was because of this slowness that at one company, Software Productions,
we compressed the menu and splash screens for our C-64 version of "Micro
Mother Goose" (sold under the Reader's Digest label). It was a simple RLE
compression, but it cut the pictures down about 70% (lots of black space around
the menu items) and decreased the load times significantly even accounting for
the extra code to decompress the images. We had plenty of RAM and loads of
disk space, it was squished purely to speed up the load.
-ethan
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16 Mar
16 Mar
10:04 a.m.
Hi,
Interesting, I always wondered why they had moved away from the IEEE bus.
I'd always assumed they'd done it in an attempt to reduce costs (those IEEE
cables weren't cheap) and to try and lock users into using CBM peripherals.
>...."serial" bus is actually a bastardised implementation
>>of the IEEE-488 bus, which CBM had used on the PET series.
Caused, IIRC, by Tramiel who demanded of the engineers that
the next computer not use the same connectors because of a
supplier shortage.... There's a great book on the PET and its
implementation of the
IEEE-488 bus by Osborne Press. If you ever see a copy of it at
a bookstore or flea market and have even considered programming
for the PET, grab it.
I *THINK* I've got that book (came with one of my PETs). I can't remember
the title now ("PET IEEE Interfacing"?), but it goes into a lot of detail on
how the bus works and includes several practical examples.
Hang on....goes off to have a rummage....dammit, can't get at it right now.
:-(
It was because of this slowness that at one company,
Software
Productions, we compressed the menu and splash screens for our
C-64 version of "Micro Mother Goose" (sold under the Reader's
Digest label). It was a simple RLE compression, but it cut the
pictures down about 70%....
Yes, I did some work for a local company called "Novagen" back in '85 which
was pretty similar.
In this case we were putting the Atari 8-bit version of "Mercenary" onto
cassette and wanted to display a logo screen while the game was loading. I
wrote a very simple RLE compression program to allow us to load the screen
in a reasonable amount of time....there was an awful lot of green in my logo
so it compressed VERY well. :-))
That was the first time I made any money from programming.
TTFN - Pete.
--
Hardware & Software Engineer. Sound Engineer.
Collector of Arcade Machines, Games Consoles & Obsolete Computers (esp DEC)
peter.pachla(a)wintermute.org.uk | www.wintermute.org.uk
--
12:12 p.m.
::Yes, I did some work for a local company called "Novagen" back in '85
which
::was pretty similar.
Ha, Novagen! Did you ever hear of Novaload while you were there? That and
Turbo Tape were mucho popular tape loaders. I have a Commodore-branded
sound synthesiser program that has a Novagen loader.
--
----------------------------- personal page: http://www.armory.com/~spectre/ --
Cameron Kaiser * Point Loma Nazarene University * ckaiser(a)ptloma.edu
-- Not sun-worshippers: Son-worshippers! -- Uhura, Star Trek "Bread &
Circuses"
8893
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ckaiser＠oa.ptloma.edu -
ethan_dicks＠yahoo.com -
peter.pachla＠wintermute.org.uk