usb printer

[bruce woller]

On Monday, June 23, 2003, at 11:41  PM, Stephen Harker wrote:
>  it is not clear to me why some people
> have problems and others not.  Can you get anything out of the
> printer, even a test page?

Hi Stephen and Manoux:

I experience the same printing problems (USB Epson C80).  My suspicion 
is that the incomplete print or paper spewing problem is a USB driver 
issue.  Reading up on Epson printers I found that when using Mac Os 
drivers the print data is sent packetized, i.e. there is a checksum 
associated with each data packet and the printer has the capability to 
request the resend of any data that fails the checksum test.  Under 
CUPS the data is sent to the printer "ship and pray" i.e. there is no 
check on the validity of the data sent over the USB interface.  If the 
data is incorrect the printer can interpret it as commands that were 
not intended by the driver.  I only see these issues with old G3 B&W 
(yosemite) machines.  I don't know if these machines have different USB 
hardware or not.

Regards,
Bruce