Performance Considerations - Printronix L5000 Series Maintenance Manual

Performance Considerations

The printer prints 8.5" x 11" fan–fold paper at 24 pages per minute portrait (one page
every 2.5 seconds) and 31 pages per minute landscape. To sustain printing at full
speed, data for each page must be received and rendered in less than 2.5 seconds for
portrait mode (otherwise the printer will pause).
Failure to print at full speed may be caused by one or more of the following:
an inefficient application program
an insufficient Communication Interface Bandwidth
a slow host computer
a low priority on the host printer port or printing task
a highly complex print job, usually containing a large number of characters and
graphics that exceeds the bandwidth of the controller
An inefficient application program is listed first because a highly efficient program
sends fewer characters to the printer than a less effective program, and it can be used
to overcome the other four causes of performance problems. This is especially true of
IGP/VGL and IGP/PGL applications, due to the power of these printer emulations. In
many cases, converting a program from IGP/VGL to IGP/PGL results in substantial
performance improvements.
Wide width printing jobs with a large number of characters on a page can exceed the
communication bandwidth and/or the communication speed of the host computer. A
plain text print job of 132 columns by 66 lines requires a sustained data transmission
rate of 3485 characters per second, or for serial communication a sustained
throughput of 34.85 KBaud (assuming 8 bits of data, 1 Stop Bit, 1 Start Bit, and no
Parity Bit). In this case, RS232 would be an unacceptable selection for
communication because the maximum RS232 Baud Rate of 19.2 KBaud is less than
the required 34.85 KBaud sustained throughput. Selecting either RS422 or
Centronics Parallel may solve the communication bandwidth problem but may not
solve the overall system performance problem.
Sustaining high communication data transfer rates may require the host computer to
be tuned to meet the printer's speed requirements. On mini or mainframe computers,
printer performance problems can usually be solved by having the system
administrator perform one or more of the following:
F–4 Host I/O Interfaces