New Developments in Parallel Ports in HTML
Parallel Port Information System version 1.45 Jay Lowe and Don Schuman 27 Oct 1994
Application Note 062 IEEE 1284 – Updating the PC Parallel Port
Interfacing Articles by Craig Peacock
Interfacing the Standard Parallel Port
Interfacing the Enhanced Parallel Port
Interfacing the Extended Capabilities Port
SCB Architecture January 1991 (95A ExpressPrint port can use SCB)
Introduction, Overview, and Capabilities
Locate Mode Overview, Physical, Delivery, and Processing Levels, Design Considerations
Move Mode Physical, Delivery, and Processing Levels, Design Considerations,
Folks, recent investigations into parallel port modes has revealed virtual SCSI ports used with products based on Shuttle Technologies' chipset (bought by SCM Microsystems, IIRC). This exposed the distaste of NT4 for ECP. Perhaps Shuttle sidestepped this limitation by "fooling" NT4 with a virtual "SCSI" port. There are many products made in the early to mid-90s with Shuttle Parallel-to-SCSI adapters.... Possibly the portable parallel CDROMs are IDE based... hmm...
Dual Async/Parallel Adapter 2
Bidirectional Parallel Adapter
When my Parallel to CF adapter arrives, I can test it on a Type 4 (95A ExpressPrint) port.
Updated W95 Printer Driver
Direct Cable Connection
DMA Printer Port (Uncut!)
Checking for DMA Use
Two Parallel Ports under W98SE
Boca Parallel Cards in Server 720
Parallel Port Pinout
Parallel 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 port.
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."
Parallel Port Address Assignments
Parallel_x has been shortened to Par_x so the table fits.
Type 1 ports do not support DMA.
Type 2 Parallel_1 does not support DMA, Arbitration Level is fixed at Arb 6.
Type 3 Parallel_1 DMA Disabled (03BCh) -OR- DMA Enabled (1278h), full Arb levels
NOTE: 03BCh was used by the parallel port on the (old) Monochrome Display Adapter (MDA). I suspect that in certain video modes, placing Extended Mode registers on 03BCh would interfere with video memory.
Updated W95 Printer Driver
Found this on Russ Wright's Cannon Support Pages
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 port’s Resources properties), as shown in the following list.
Basic *.inf Configuration(s)
To enable ECP support in
Direct Cable Connection
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!
DMA 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 practically 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.
Checking 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.
Dr. Jim Shorney (on sabbatical)
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
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 family HERE.
> Peter, is there a patch that allows the reconfiguration of the parallel port to bidirectional?
Err ... PS/2 sysboard LPT are bidirectional by nature.
There are 3 registers used on LPT ports:
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
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
Boca 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 his 720.
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
>Unfortunately, the instructions warn not to use it
in a 32 bit slot as damage might result to card or
Parallel Port Connector Pinout
*** Data parity is a function of parallel port A
Parallel Port Addresses vs. Modes
Compatible is the
old-styled unidirectional printer port
ADF Settings for Parallel Ports
Not all systems support these settings, nor will they be in the same order.
Parallel Port x
Parallel Port x DMA
Parallel Port x SCB I/O