very, very slow sending to printer

[Gary Carroll]

I am building PostScript print jobs that when printed to a Konica 
Minolta 1050 will produce folded, stapled and trimmed 8.5 x 11 inch 
booklets. The imposition is done in an application that builds it from 
multiple “print to file” jobs done by other people. Since I have no 
control over the input, and the multiple jobs are through different 
drivers / operating systems the application spends considerable effort 
converting them into clean PostScript, then imposing the PS and wrapping 
it in the commands to finish it properly, and the final imposed job is 
quite large.
Sending the job to the printer produced the correct output, but took 
forever. I observed from the system monitor that I was averaging about 
60 kilobits per second to the printer. However, when sending the same 
job to a Windows printer queue (or a shared folder on a Windows 
computer) I got around 10 megabytes per second. If I sent from the 
Windows computer to the printer I got about the same 10 megabytes per 
second. Currently the fastest method by far is to print using the 
Windows machine as a print server.
I did test for bad connectivity at the printer end by moving the patch 
cable going to the printer to a laptop running an LPR queue: I got 10 
megabytes/sec from both the Windows and the Linux boxes. The problem is 
Linux/CUPs talking to the printer. Linux to Windows or Windows to 
printer is fine.

Though I am a Linux newbie, this does not seem right. Where should I be 
looking for my problem? The printer manufacturer is no help, at least, 
not in the short term.

Running Fedora Core 5, on a Sun Fire X2100 (2GHz Opteron) with gigabit 
Ethernet. (The printer has only 10/100.)
The Windows tested was XP Pro on an identical X2100 (and also the 
laptop, a Pentium 4).