🚀 go-pugleaf

v087mxgb@ubvmsa.cc.buffalo.edu (Shawn E Thompson) writes:

> In article <6117@spdcc.SPDCC.COM>, jin@spdcc.COM (Jerry Natowitz) writes...
> >I have an Epson LQ800 printer that I will connecting to my not yet
> >received PC.  Is there any performance advantage to using the parallel
> 
> YES. Parallel can run up to 8 (I think) streams of data
> in synchronicity, where serial can run one.

    Parallel does not run 8 streams of data. It runs one. It can carry
all 8 bits of the one stream of data at one time, whereas serial
presents this one stream of data one bit at a time. 

    The main advantage of parallel is that it is a handshook data path.
That means that when the sender puts data on the lines, it says "here it
is". THe recipient takes it off the line and then says "thanks I got
it." The recipient can also say "don't send me anything right now I
can't take it". The path can be faster than serial, since the sender
doesn't put each piece of data out for a fixed length of time -- it
sends the next piece as soon as the recipient has the last. It can also
be slower, if the recipient is slow at acknowledging. 

   Serial data is sent one bit at a time, with each bit being presented
for a fixed length of time. It doesn't matter if the recipient can take
data faster, you are limited by the baud rate on the serial line. 

   The only advantage you will see when using a character printer is
that you can fill its buffer faster, and the system will think printing
is finished sooner. If your printer can print 240 cps, you won't
actually finish printing any sooner whether you use 2400 baud serial or
parallel. But, the faster you fill the buffer to the printer, the faster
your computer will be free to do other things. 

   The other advantage to parallel over serial is that parallel has only
ONE wiring method, and only ONE handshake system, where serial has
X-ON/X-OFF and RTS/CTS and about a dozen different ways to wire a cable.

   Now, one advantage to serial that parallel does not have is that serial
is bi-directional. If you have a fancy new PostScript printer, it likes
to send error reports back to the host. It can do this over a serial line.