COMPUTE! ISSUE 58 / MARCH 1985 / PAGE 10
Commodore Baud Rates
I own a 64 and am interested in purchasing a modem. It seems the only
modems available are 300 baud modems. Why is this? Can the 64 only
operate at 300 baud?
Ki Jeong Yun
When using ordinary telephone lines,
a communications rate of 300 baud (more properly, 300 bits per
second-bps for short) is the most reliable. In addition, 300 bps modems
are much more affordable than faster modems, and the 64 is a low-cost
computer aimed at the home market. A 1200 bps modem would easily cost
more than the computer itself.
The problem is
that higher transmission rates pack the data more densely and therefore
are more susceptible to errors from line noise. At 300 bps, only about
30 characters per second are transmitted. At 1200 bps, about 120
characters per second are sent, and a short burst of noise could cause
a significant loss of data.
Also, it's
important to remember that both ends of any telecommunications link
must operate at the same speed. If you have a 1200 bps modem while most
other 64 owners have the more common 300 bps modems, you'll be able to
use the higher speed to communicate with only a limited number of other
users.
The Commodore 64
is actually capable of exchanging data at up to 2400 bps through its
serial port. By using the proper interface, it is possible to attach
any RS-232 compatible modem to a 64 and program the port for whatever
rate you wish. The quality of the phone line will be the limiting
factor.
If you're shopping
for a faster modem, watch for prices to drop significantly on 1200 bps
modems in 1985. Several companies also introduced 2400 bps modems at
the Fall COMDEX computer show in Las Vegas last November, but they're
priced in the $800 range.