16 Mar
2000
16 Mar
'00
12:40 a.m.
Not sure what happened last time I sent this. I'll try again...
The "serial" bus is actually a bastardised
implementation of the IEEE-488
bus, which CBM had used on the PET series. Data is transferred serially (at
300 baud) instead of in parallel, other than that I believe it's pretty much
IEEE.
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 - I never had problems with 4800 baud in software on a PET.)
Philip.
**********************************************************************
This email and any files transmitted with it are confidential and
intended solely for the use of the individual or entity to whom they
are addressed. If you have received this email in error please notify
the system manager.
This footnote also confirms that this email message has been swept
for the presence of computer viruses.
Power Technology Centre, Ratcliffe-on-Soar,
Nottingham, NG11 0EE, UK
Tel: +44 (0)115 936 2000
http://www.powertech.co.uk
**********************************************************************
16 Mar
16 Mar
9:32 a.m.
Hi Philip,
....Are you _sure_ it's 300 baud? I thought it was
2400....
Well, it has been a few years since I had much to do with the C64 so my
memory could be faulty. I definitely remember a figure of 300 baud quoted
somewhere in relation to storage though....perhaps that's the rate that the
cassette system runs at?
I know very little about CBMs cassette system, all my programming was
related to the disc and cartridge systems.
....Same load module from tape took SEVEN minutes! No
wonder
speed loaders and things were popular!
No kidding. I remember when systems like "NovaLoad" came along allowing
games to load from tape faster than they did from disc. And then the
floodgates opened....
....doubling the throughput. May have used higher baud
rate as
well - I never had problems with 4800 baud in software on a PET.
Hmm, memory is hazy now, but I think cartridges like Epyx' "FastLoad" did
use a higher than normal baud rate when running in fast mode (bear in mind
that it's probably 11 years since I last used my FastLoad cart).
I only heard of this trick of using two lines on the serial bus to double
the data transfer rate quite recently. AFAIR the serial bus already uses two
data lines, one for data out of the C64 and a second for data in?
Would I be right in assuming that this trick involves using both lines as
inputs or outputs simultaneously?
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
--
12:17 p.m.
:: >....Are you _sure_ it's 300 baud? I thought it was 2400....
::
::Well, it has been a few years since I had much to do with the C64 so my
::memory could be faulty. I definitely remember a figure of 300 baud quoted
::somewhere in relation to storage though....perhaps that's the rate that the
::cassette system runs at?
Yup yup yup. I must have missed the original message. The IEC bus is much
faster than that, and of course fast serial devices like the 128 (in 128 mode)
coupled with burst-capable devices like 1571s and 1581s are faster still.
A quick hardware mod will let you use high speed transfers on the 64 too (with
software to drive it, the Kernal doesn't know how).
::No kidding. I remember when systems like "NovaLoad" came along allowing
::games to load from tape faster than they did from disc. And then the
::floodgates opened....
So you *do* know about Novaload! (Ignore previous message.) Who wrote it?
Do you remember?
::Hmm, memory is hazy now, but I think cartridges like Epyx' "FastLoad" did
::use a higher than normal baud rate when running in fast mode (bear in mind
::that it's probably 11 years since I last used my FastLoad cart).
::
::I only heard of this trick of using two lines on the serial bus to double
::the data transfer rate quite recently. AFAIR the serial bus already uses two
::data lines, one for data out of the C64 and a second for data in?
::
::Would I be right in assuming that this trick involves using both lines as
::inputs or outputs simultaneously?
I don't remember the details of how it works, but yes, FastLoad steals
another IEC serial bus line and uses it for an extra bit of transfer. On
every load it shuffles a small ML subroutine into drive RAM and executes
that so the disk drive knows how to do the transfer. It achieves ~5x
increase that way, and is *highly* compatible.
What I suspect it uses is the ATN line. Don't ask me how, it just rings
a bell for some reason.
--
----------------------------- personal page: http://www.armory.com/~spectre/ --
Cameron Kaiser * Point Loma Nazarene University * ckaiser(a)ptloma.edu
-- If ignorance is bliss, shouldn't I be happier? -----------------------------
17 Mar
17 Mar
8:58 a.m.
Hi Cameron,
Yup yup yup. I must have missed the original message.
The
IEC bus is much faster than that....
I've had a rummage but I can't find my copy of the C-64 progref at the
moment. However, according to "The Anatomy of the 1541 Disc Drive" the
standard transfer rate across the serial bus is around 400 bytes per second.
Assuming no stop/start/parity bits and 8-bit characters, that's 3200 baud.
Same book also quotes 1.8K per second for the PETs IEEE/GPIB bus.
....and of course fast serial devices like the 128 (in
128
mode) coupled with burst-capable devices....
I had a 128D in '87, transfer rates were excellent when running the system
in 128 mode (almost comparable with the Atari serial bus), but like most
people I ran the system mostly in C-64 mode....I'd actually gotten it to run
CP/M, but that's another story.
So you *do* know about Novaload! (Ignore previous
message.) Who
wrote it? Do you remember?
Yep, that was Paul Woakes....he WAS Novagen (and still lives about 25
minutes walk away from me).
Paul wrote the vast majority of the software Novagen released himself. For
example, "Mercenary" was released on just about every 8-bit format around in
1985/6. The only versions Paul didn't write himself were the Z-80 ports for
Amstrad and Spectrum.
In fact, Novagen only released two games which weren't entirely Paul Woakes
productions. "Backlash" which was my idea and I did most of the original
work on, and a scrolling shoot-em-up (the name of which I forget) which a
friend of mine wrote.
I don't remember the details of how it works, but
yes, FastLoad
steals another IEC serial bus line....
....I suspect it uses is the ATN line. Don't ask me how, it just
rings a bell for some reason.
As I said, I can't find my progref manual so I can't check the schematics.
However, I'd suspect it uses another line since ATN is used as an output
from the machine to tell devices on the bus that a
command is about to be
issued. I'd suspect it probably uses "SRQ IN",
I believe this line is
normally unused?
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
--
7:08 p.m.
New subject: Boxes of C64/128 software.
I bought two large boxes of C64/128 software today. Most of it looks pretty
new in the box, but I couldn't fit all of it into the two moving boxes I
had, so really bulky items like TimeWorks got the packaging tossed. If
somebody is looking for something, email me before it lands on eBay.
8898
days inactive
8900
days old
4 comments
4 participants
participants (4)
-
ckaiser＠oa.ptloma.edu -
mikeford＠socal.rr.com -
peter.pachla＠wintermute.org.uk -
Philip.Belben＠powertech.co.uk