New Developments in Parallel Ports Douglas Boling,
PC Mag Oct 27, 1992
Parallel Port Information System
version 1.45 Jay Lowe and Don Schuman 27 Oct 1994
Direct Cable Connection
DMA Printer Port
Checking for DMA
Ports under W98SE
Boca Parallel Cards in
Port Addresses vs. Modes
95A Parallel Ports
Port "A" (bottom parallel port) is an ExpressPrint
Parallel Port that supports IEEE 1284 (P) compliant
devices at up to 2MB/s. Using vendor supplied
multiplexer and software, users can attach up to four
supported printers and output 300 dpi complex graphics at
the rated speed of the printer and still have capacity
left over. Compared to a direct LAN attachment, where data
is sent over the LAN twice before being printed, the
busmaster ExpressPrint Parallel Port not only reduces the
load on the server processor, but prevents the LAN from
being flooded with unnecessary printer traffic.
Port "B" (top parallel port) is a standard parallel
If you experience a problem with a non-IBM device when
attaching it to either the parallel port, you might need
to go to the Change configuration screen of the system
programs and set the port DMA (direct memory access)
arbitration level to "Disabled."
W95 Printer Driver
Found this on Russ Wright's Cannon
Microsoft released a newer version of
the LPT.VXD file for Windows 95 the LPT.VXD is located in
the SYSTEM directory
This LPT.VXD is to replace the version
provided in the Windows 95 service pack #1 and is newer
than the version provided with Windows 95 OEM or OSR2.x
This latest LPT.VXD is version 4.00.955
Click here to download the file A5318.EXE
this file contains PRNT5UPD.EXE and README.TXT
Windows 95 Printing Extended
Capabilities Port Support
(Ed. Applies ONLY to
LPT A on 95A systems!)
An ECP provides high-speed printing, and
support for ECP and ECP devices is included in Windows 95.
If you have an ECP, you can connect either ECP or non-ECP
devices to the port. In either case, using an ECP will
improve I/O performance, although ECP devices will show
the greatest I/O gains. An ECP can be configured in five
different ways (defined in the portís Resources
properties), as shown in the following list.
Basic *.inf Configuration(s)
0 Standard I/O ranges for LPT ports only
1 Standard I/O ranges for LPT ports and any
2 Standard I/O ranges for LPT ports, IRQ, and
3 Any I/O ranges for LPT ports only
4 Any I/O ranges for LPT ports and any IRQ
To enable ECP support in
1. Consult your computer (or add-in card) manual to
determine the IRQ and DMA settings selected for each of
the ECP ports you want to use. Youíll need this
information to enable ECP support.
2. In the System option in Control Panel, click the
Device Manager tab.
3. Click Ports (COM & LPT), and then select the ECP
4. Click Properties, and then click the Resources tab.
This dialog box shows an I/O range that has been
5. In the Settings Based On field, select Basic
Configuration 2. (See the previous table for a
description of possible settings for this field.)
6. In the Resource Settings list, click Interrupt
Request, and then click Change Settings.
7. In the Edit Interrupt Request dialog box, type the
IRQ value you noted in step 1, and then click OK.
8. In the Resources properties, click Direct Memory
9. In the Edit Direct Memory Access dialog box, type the
DMA value you noted in step 1, and then click OK.
10. Reboot so the changes can take effect. After
restarting, you can take advantage of fast I/O
capabilities offered by the ECP.
I've used DCC under W95 to hook up a 9533 to a 77s.
A 76s to a 77s. Go to the very detailed Connect
Pages at Kime.Net to find out how! Sure beats the
hell out of SneakerNet for 70+MB!
Parallel Port (Uncut!)
With apologies to "The Micro Channel Architecture
Handbook" ISBN 0-13-583493-2, pages 99-100. Spelling
mistakes are probably mine.
"A practical application of Micro Channel
technology that breaks the microprocessor bottleneck in
printing is making the printer port into a DMA that uses
a Direct Memory Access controller to move the data.
During a print job, the DMA printer port would briefly
take control of the bus, shuttle the data across, and
step out of the way.
The load on the bus itself would
immediately be reduced by this technology, but that's
only of the tiniest benefit to system performance. This
sort of advanced printer port trims the overhead on the
bus because it requires only the equivalent of 68,000
characters per second in bus time to support the same
100,000 characters per second data rate. Fewer
instructions than characters are required because a
16-bit DMA bus master would be able to move two
characters at a time to the printer port instead of the
single character permitted by most printer ports in
classic bus systems. (Overhead mitigates the two-to-one
theoretical advantage of the double-width bus.) Of
course, this increase in bus width and consequent
bandwidth saving is only an implementation issue more
significant with multitasking.
The important increase in performance to
the single-tasking system comes from savings in
microprocessor useage. Nearly all of the millions of
instructions per second used in the classic bus scenario
could be freed up from the microprocessor by the bus
master DMA printer port. The microprocessor would need
to do nothing but spend a few thousand cycles to set up
the DMA transfer, rather than continuously churning
through millions of instructions every second. The DMA
controller itself would do all the dirty work. The
instructions it races through would not impact system
performance at all.
All the time that the adapter and DMA
controller are not putting data on the bus most of the
time, considering that less than 1/10th (in truth,
closer to 1/20th) of the bus bandwidth is used for
actual transfer of characters per task. Instead of being
fully loaded and unable to perform other tasks with any
speed at all, the system with a DMA printer port would
have more than 90 percent of it's potential available
while the printer is running full speed. If the
microprocessor has it's own cache memory, the impact on
system performance would be even less, potentially zero.
The economics of adding a DMA printer port
to a high-performance Micro Channel computer are
astounding. The parts required to make a DMA printer
port are insignificant compared to the cost of an
80386-based computer. As a result, in practical terma a
DMA printer adapter could buy back most of that system's
performance for less than one percent of the total
system cost. In effect, DMA buys you the performance of
another 80386-based computer for pratically nothing.
A true bus master printer port would save
more bus cycles and might be easily justified in a
multitasking or multiuser system where bus cycles are at
a premium. Remember that as earlier stated I/O transfers
can take 5 or perhaps 10 percent of the bus bandwidth per task. This means that
5 or 10 tasks might consume a sizeable portion of bus
bandwidth at the expense of performance overall. In the
single-tasking system, however, the delays introduced by
the processor-dependent I/O adapters can be
cost-effectively overcome by DMA.
for Parallel DMA Use
Q. I know that the 56/57/76/77/85/90/95 systems use serial
and parallel ports capable of high-speed DMA transfers,
but how do I know if my system is set up to use DMA?
A. Simple. Start the System Program (either from
the System Partition on your hard disk drive, or the
Refdisk), and look at the Arbitration Level for the
serial and parallel ports. The parallel port should be
set to Shared 7, and the serial port should be set to
Shared 4 for Transmit Arb Level, and Shared 3 for
Receive Arb Level. If your system has two DMA
serial ports, the second serial port should be set to
Shared 6 for Transmit Arb Level, and Shared 5 for
Receive Arb Level. These are the defaults.
If the ports are set this way, they are using DMA.
Two Parallel Ports under W98SE
How do I ensure both my parallel ports are enabled on a
Dr. Jim Shorney (on sabbatical)
Actually, use of the LPT interrupts is
software dependent. Windows' 'standard parallel
port', by default, is PIO and does not use
interrupts. Just set one up last night while
trying to help Art, and I was able to install both
parallel ports as 'standard' with no exclamation
I got it using Jim's procedure with a few
twists... I made the port setting changes in system
setup but left DMA turned on because video manufacturer
says I need ECP through DMA on the port for best
performance. Next I booted system, went in ControlPanel
and added a new ECP port. However, when checking the
port in ControlPanel/System I did have an exclamation
point on the new ECP port.
I had to then change the ECP port @ manually
under the resources tab to 278-27A. (No more conflicts).
Both the printer and video camera are working fine.
Printer on plain LPT port and camera on LPT2 (ECP) with
The Hunt for Red ExpressPrint
From: James P. Ward
982-6044 Dept. W13A ,1715, Boca Raton Fl
ExpressPrint hardware shipped with all
Vizcaya (and later... ) based systems. The 4-way
printer support is achieved thru a printshare box
from Far Point Communications in San Jose. I believe
there is a NetWare and OS /2 driver for this function
(Howard Greenberg or Mike Derwin should know). The
planner for all of this was Lew Miller. Hope this gets the
wheel rolling... Jim
The lone existing F/Mux is all I know to be
in existence. I'm not sure if Warp Nine Engineering will
ever produce it. Now that USB is out, there is less
reason than ever to do so. For more info on the F/Mux,
Parallel Resistor Networks on 95A
Bourns 4816P-001 -330 (isolated 33 ohm) and
4816P-002 -472 (bussed 4.7K ohm) for each parallel port.
Pdf for the 4800P familyHERE.
> Peter, is there a patch that allows the
reconfiguration of the parallel port to
Err ... PS/2 sysboard LPT are bidirectional by nature.
There are 3 registers used on LPT ports:
- data register (LPT-I/O +0)
- status register (LPT-I/O +1)
- control register (LPT-I/O +2)
The I/O port adress for LPT1 is usually
03BCh on PS/2, the control register is then 03BEh. (You
can determine the adress with reading the bytes at
0000:0408 and 0000:0409 in the Bios adress space - the
LSB is first, it will read BC 03).
If you set bit 5 (direction) of the control
register to 1 you can read from the bytes present at the
data-register. To permanently read from the LPT-port you
need to set the bit 0 (strobe) to 1 you get the bit
pattern changes on the port. I use that for the little
program that reads the CP codes from another
A proper handshake signalling between two
computers using the bidirectional mode will most likely
work over reading the BUSY lines from one computer to
the ACK signal on the other ... you need to read the
status of the two lines to determine, which of the two
is the sender and which receives data. This is a bit
tricky ... but some other software does that already and
uses this feature.
The PS/2 parallelport is a great device to
be used as e.g. input from a Analog-to-Digital converter
(however: only 8 bit resolution). For many simple
purposes this is truely great. I used the parallel port
to control the functions of my AKAI tape-machine ... or
used it for some other weird stuff.
The system board provides two 25-pin
D-shell connectors to the parallel port controllers on
the system board. The drivers to the data lines can
source up to 15 milliamps and sink up to 24
Parallel Card on 720
>On another subject, would you have any idea why a Boca
parallel port card won't work properly in a server
720? I tested it in my 95, and it passed wrap tests
under DOS, but my friend can't print to it from OS/2 in
Ahem ... I would say the BOCA is too
slow. Remember that the "target" machines for
these cards were the Mod. 50 - 80 with the MCA Stage 1 /
Stage 2 layout. The 720 is not even "real MCA" but a
Corollary system, which uses 80MB/s data streaming mode
on all MCA-slots. Therefore only a very limited
number of adapters has ever been announced for it. The
"normal" adapters *may* work in the 720 ... or may not.
Most worked though - but there was a number of adapters
that did not. The Boca cards use very large, very cheap
ASICS -as the most of the Multi-I/O card do- which are
known to be slow and I got reports that they even fail
on faster Mod. 80 (and 76/77, 85, 90 and 95 as
The Mod. 95 also may handle them good or not -
but the "True MCA" machines have a slightly different
mechanism / arbitration to handle slower cards than the
Corollary MCA bridge - obviously this implementation is
not 100% compatible with the MCA Stage 4 of the Mod.
9595 or the Stage 3 of the older 8595-machines.
>Unfortunately, the instructions warn not to use it
in a 32 bit slot as damage might result to card or
This card is rather old and
originally designed for the slow 10MHz-80286 machines
like Mod. 50 and 60, but will also run in 16-bit slots
in a 16 or 20MHz Mod. 80.
The "Full 32-bit" machines, like 85 /
90 / 95 run on a later and much faster
MCA-specification and therefore *might* cause damage to
the card buffering chips (those which connect the card
to the bus) due to a much to short cycle speed.
The manufacturer - aware on possible
problems and upcoming warranty issues - wrote this note
in the manual to free himself from possible loss.
Logically. All in all I would say it is not specified
and not certified to be used in a Mod. 95.
The first thing to be damaged
is the card itself - but there is the risk of getting a
sort of secondary impact on the machines' systembus
drivers, which might get permanently damaged because of
overload due to short-circuits in the adaptercard.
In case of doubt: I would not
use it. Only the manufacturer knows what might happen,
and they don't write such a (negative) passage in the
manuals just to tease the users.
Port Connector Pinout
||-Auto FD XT
*** Data parity is a function of parallel port A
Parallel Port Addresses vs. Modes
Many software drivers cannot handle
addresses outside of 278-3BF. Parallel 4 (all modes) and
the enhanced/extended Parallel 1 addresses are probably
NOT supported unless you use OS/2 or a *nix.
Parallel 1 has a primary address of
3BC-3BF. IBM says that the DMA controller does NOT
support that address, so that's where the odd 1278-127F
Compatible is the
old-styled unidirectional printer port
Enhanced is what?
Enhanced/Extended ports use DMA. I don't know what the
other difference is. Note that the enhanced port is one
bit more than a standard port. Extended ports are two
I have installed an ECP Printer Port under
"Add New Hardware". Go to the ECP Port's Resources and
select the correct address and DMA Channel. It appears
that DMA Channel 1 is used by DMA Arbitration Level 1.
Am unsure if that's true, but it still works. I don't
have a parallel port device yet to verify this other
than my digital camera.
I also hacked msports.inf in the [1aaa]
section so that I had the extended port address. Dunno
if that works better than the Compatible address, but it
"looks" faster. Odd, but the IBM manual lists the
enhanced mode, not the extended mode. The addresses in
the adf for the planar are the ones ending with a "d".
Does this mean compatible mode only? Or does it just
show the non-DMA ports? Help!
Settings for Parallel Ports
Not all systems support these settings, nor will they be
in the same order.
Parallel Port x
The parallel port x
can be set as Parallel 1 through 4 or the port can be
<Parallel 1 ( io
03bch-03bfh 1278h-127fh int 7)>, Parallel
2" (io 0378h-037fh int 7), Parallel 3 ( io
0278h-027fh int 7), Parallel 4 ( io 1378h-137fh int 7),
Parallel Port x DMA
The parallel port x
connector can be set to any one of the available DMA
arbitration levels. If the level selected is
shared then other devices can be set at the same
level. If the level selected is dedicated then
only this device can be set to that level.
level 7>, Shared level 6, Shared level 5,
Shared level 4, Shared level 3, Shared level 1, Shared
level 0, Level 7, Level 6, Level 5, Level 4, Level 3,
Level 1, Level 0, Disabled"
Parallel Port x SCB I/O
The parallel port x connector can be set to
any one of the available SCB I/O addresses.
9100-9102, 9500-9502, A100-A102, A900-A902, B100-B102,
B900-B902, C100-C102, C900-C902, D100-D102, D900-D902,
E100-E102, E900-E902, F100-F102, "Disabled
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