From: wfaust@venus.adsp.sub.org (Wolf Faust)
Newsgroups: comp.sys.amiga.hardware,comp.sys.amiga.applications
Subject: Deskjet & Laserjet
Date: 2 Jan 93 13:25:29 GMT
Organization: Not an Organization


I have made some real life tests with various HP printers and
drivers.  Maybe it's of interest.

Most (all?) of the current HP printers support several compression
schemes. Those defined by HPs latest PCL 5 docs are:

Mode 0        = None
Mode 1        = RLE
Mode 2        = Packbits (RLE)
Mode 3        = Delta row
Mode 5 (ERGS) = Adaptive Compression

Compression schemes can be switched from row to row, or color to
color.  This allows drivers to select the best compression method
for each raster row (for instances Studios mode 0+2+3).

Here are some timings made while printing a DTP/word processor
page full with text and graphics on a HPIIIP (Deskjet timings do
have the same relationship):

                       Print Data Size   Print time

Mode 0                   523428         44.08 seconds
Mode 0+2                 220974         22.98 seconds
Mode 3                   122531         15.26 seconds
Mode 0+2+3               119996         14.44 seconds
Mode 5 (ERGS)            106419         10.40 seconds

As you can see, the data size and print time have been dramaticly
reduced, resulting in a major speed increase when using 0+2+3 or ERGS.

While the compression ratio looks good for DTP and word
processing stuff, it may come out worse for pictures.  In a worse
case there might be lot's of CPU power wasted for nothing.  So I
printed a dark 8 Bit DIN A4 picture with various drivers and
a floyd dither (hard to compress ;-):

            Data Size   Computing/Transfer/Total Time      Transfer rate
Studio:
Mode 0       621645       2:43 / 44 sec / 3:27            14 KBytes/sec
Mode 0+2     543024       2:44 / 38 sec / 3:22            14 KBytes/sec
Mode 0+3     407637       2:43 / 41 sec / 3:24            10 KBytes/sec
Mode 0+2+3   398001       2:45 / 39 sec / 3:24            10 KBytes/sec
Mode 5 ERGS  389227       2:35 / 27 sec / 3:02            14 KBytes/sec

DJHelper:
Mode 2       543904       2:45 / 38 sec / 3:23            14 KBytes/sec

Commo HP_Laserjet:
Mode 0       620216       2:44 / 44 sec / 3:28            14 KBytes/sec

Commo HP500/550C:
Mode 0       621611       2:45 / 44 sec / 3:29            14 KBytes/sec

As you can see, even in worse case compression does not cause a
slowdown.  All driver have nearly the same speed (except Studios
ERGS) because of the worse compression.

Some interesting things should be noted:  the transfer rate of HP
printers depend on the compression scheme used.  Also, Mode 5 ERGS
is unpacked by the HPIIIP during print time, allowing you to
print high resolution pictures with a standard 1MByte equiped HP
IIIP.  This also results in a good transfer rate, though, the
compression method used in mode 5 is nearly the same as mode
0+2+3.

Mode 5 requires less computing time because of the internal
buffering of the Studio driver.  Data is send to the printer in
~32767 Bytes blocks.

-- 
Wolf Faust                 Internet: wfaust@aurea.hotb.sub.org
Germany                        FIDO: 2:249/3.5
Tel: (+49)69 5486556         CBMNet: wfaust@venus.adsp.sub.org