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Subject: DMA-channels
Name: MS
Date: 1/14/2007 7:52:12 AM (GMT-7)
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In Reply to: Re: More Thoughts posted by Connie

The parallel port is a legacy device that is not even fully supported any more on the chipset level. Instead, it is running over what is called the LPC bus and an LPC controller that was created to extend the shelf life of ISA protocol - bound applications by Intel back in '96.

The problems with this type of application is that sometimes, they grab a memory channel and don't release it until all data are transferred, in the case of the UPS label, I believe it is a bitmap format that is of pretty insane proportions and that needs to be fed through a really slow bus to the printer. The bottleneck in this case seems the parallel "cable" to the printer, that is, the connection between the controller and the printer's receiver.

Most likely, if you get yourself one of these cheap print servers (there are even wireless ones now), you completely eliminate the problem because everything is transferred over ethernet in one sweep. Another possibility is to increase the amount of memory in your printer, I print UPS labels and it doesn't lock up the system at all (and my box is from 2001)

Last, you have to check your parallel port settings, only ECP does support DMA access, if you are running in EPP or SPP mode, you will always sit there waiting.

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