many newer motherboards have a FIFO for use with the Parallelport. This FIFO
reliefs the CPU from doing the software handshake by doing hardware
handshake by itself. There is a standard register layout for these
additional registers, so probing for these registers can be done without
knowing the special hardware. Using this fifo is known as "Fast Centronics"
or so.
I have extended drivers/char/lp.c to use this feature, where available.
This improves writing in the High speed mode of a Laserjet 4 Plus:
bash# time dd if=/dev/zero of=/dev/lp1 bs=1k count=1k (without FIFO)
0.00user 11.11system 0:11.17elapsed 99%CPU
bash# time dd if=/dev/zero of=/dev/lp1 bs=1k count=1k
0.00user 0.69system 0:08.13elapsed 8%CPU (with FIFO)
Here the data for the standard speed of a HP Laserjet 4 Plus:
bash# time dd if=/dev/zero of=/dev/lp1 bs=1k count=100 (without FIFO)
0.00user 1.92system 0:02.06elapsed 93%CPU
bash# time dd if=/dev/zero of=/dev/lp1 bs=1k count=100
0.00user 1.24system 0:01.27elapsed 97%CPU (with FIFO *)
bash# time dd if=/dev/zero of=/dev/lp1 bs=1k count=100
0.00user 0.41system 0:01.27elapsed 32%CPU (with FIFO and Interrupt)
(* timeout set to 0 )
If you are interessted to test this extension, please let me know. I need
testers with old hardware too, to test compatibility.
I will send you these following files: lp.c, lp.h and
tunelp-1.3/tunelp.c. Best is to have lp as a loadable modules. With the
modified tunelp, you can enable the usage of the FIFO.
> bash# /home/bon/tmp/tunelp-1.3/tunelp /dev/lp1 -f on
> /dev/lp1 using polling on fifo
The availability of a FIFO is reported when inserting the driver:
> May 13 19:53:10 elektron kernel: lp1 at 0x0378 has ECP-Mode(polling)
> May 13 19:53:10 elektron kernel: lp2 at 0x0278 (polling)
If you have a IEEE1284 compatible device connected to
you Parallelport, which allows mode-negotiation, the result of this
negotiation will be printed when opening /dev/lpx. I don't have such a device.
-- Uwe Bonnes bon@elektron.ikp.physik.th-darmstadt.deInstitut fuer Kernphysik Schlossgartenstrasse 9 64289 Darmstadt --------- Tel. 06151 162516 -------- Fax. 06151 164321 ----------