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OT(?) FC2 Very slow printing to HP DeskJet 870Cse

I have done further investigation, and it appears that there
must be something wrong with the setup. The printer is indeed
not a postscript capable printer, so some preprocessing/rendering
is being done on the computer, and a graphical image is
being sent. The slownes is not due to CPU bottleneck, as
shown by top:

Cpu(s):  1.7% us,  5.0% sy,  0.0% ni, 93.3% id,  0.0% wa,  0.0% hi,  0.0% si

Copying text files directly to /dev/lp0 results in very fast
printing (the files must first be run through unix2dos to put
in the CRs). So the problem is not just a slow interface on
a byte-by-byte basis.

The usual Epson standard for transferring graphics images
(which I presume, but have not checked) this printer uses
is a bit-for-bit technique (almost). Since the printer is
300x300 bpi, and a full page has 1/4" margins top, bottom,
and sides, that's 8x10x300x300 = 7200000 bits. Dividing
by 8 bits transferred = 900000 bytes to transfer.

The Centronics spec shows that the minimum time to transfer
a byte is 2.75us, so the entire page must take at least
2.475 seconds to transfer. But I'm seeing 30 minutes.

So this achieves only 0.1375% of the maximum speed.

Something is wrong.

A few days ago, immediately after a reboot, I found that
a page printed in about 30 seconds. It was definitely
printing as a bit image. Now I'm back to 30 minutes
per page.

Can anyone point to help on configuring the printer device?
Perhaps interrupts are disabled, or sth the like.

This message made from 100% recycled bits.
You have found the bank of Larn.
I can explain it for you, but I can't understand it for you.
I speak only for myself, and I am unanimous in that!

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