Anzac IPDS Rationale and Architecture

IPDS was introduced in the infancy of the laser printing industry. First specifications appeared as part of Systems Application Architecture, (SAA) in 1984. SAA was a fundamental set of rules and standards that IBM said they would follow for the future. If System designers and application programmers complied with these standards, they would be able to transport their applications to any IBM platform of the future.

In 1984, IBM was selling the IBM System 36, 38, Series 1, IBM PC, IBM mainframes and some smaller, more specialized computers. In most cases, there was no cross-compatibility between these systems for disk, tape, workstation or printer attachment. For example, if you replaced an IBM System 36 with a mainframe, you changed all the hardware, including all the cabling to the workstations and printers!

In 1984, you may recall, we were all marveling at the phenomenal speed of the IBM PC XT. Lasers, incorporating state-of-the-art microprocessors at the time, were able to almost silently print plain text at enormous speed compared to other desktop printers of the time. (Remember daisy wheel printers?) The IBM 3812-2, which was rated at a maximum speed of 12 pages per minute, printed text at 8 pages per minute. However, relatively simple graphics slowed the printer to less than one page per minute!

At the time, it was acceptable to wait for 15 minutes for a page to be printed on a desktop publishing laser. But for business purposes, where paper production is to a schedule, IPDS graphics simply did not print fast enough. Most companies stayed with preprinted forms.

Today, microprocessors are hundreds of times faster than they were in 1984. While the most visible and obvious improvement has been in the PC marketplace (from the IBM XT to the Pentium), similar performance enhancement has taken place in the microprocessors used at the heart of laser printer controllers. Laser printers today have motherboards, or controllers, that are hundreds of times faster than they were ten years ago.

As well, the laser printer controller market has grown in the past ten years into the largest market in the world for high performance RISC processors. These high speed processors can now calculate graphics faster than the laser engine can print them. In the PC and Macintosh marketplace, these performance improvements have dramatically improved the productivity of desktop publishing, reducing print times from 15 minutes for a page down to seconds. At the same time, this performance has led to the growth of a forms overlay industry which offers real-time printing solutions on lasers for everything from forms production to check printing.


 

So why are IPDS laser printers still so slow when performing graphics printing?

The development of an IPDS controller takes between 22 and 72 man-years, according to the companies who have undertaken such a development. This means that most IPDS designs are at least 5 years old, and are not utilizing current, high speed microprocessors. The huge improvements in microprocessor performance are irrelevant unless the designs are updated.

In the past, IPDS designs have taken so long to complete, the technology was out of date by the time it got to market. In five years of development, the target printer engine would have been end-of-lifed, to be replaced by a newer model. As a result, the new target printer would be a compromise.

As well, only one company outside IBM to my knowledge implemented a true IBM-compatible product, which they properly supported. The company was Decision Data. However, the performance issues were never resolved. Every other IPDS implementation was incomplete, and poorly supported, as though it was such an effort to complete the development, there was no energy left to complete the project or fix the bugs.


So why is the Anzac IPDS solution so much better?

Speed of development. The entire Anzac development was completed in 16 months! That is, both the hardware design and the IPDS software interpreter. Accordingly, the design is absolutely current and to-the-minute.

Taking advantage of leading edge performance. The hardware for Anzac's new IPDS controller was designed in 1994, and utilizes very current microprocessor design. Anzac's IPDS interpreter, which resides on the Anzac IPDS controller, works in total harmony with the RISC processor on the printer's motherboard, using it to perform the massive number crunching required for graphics and imaging. The end result is impressive performance. For example, the slowest Anzac laser is about four times as fast as the IBM 3916 when processing a page of imaging. If you are on the phone, waiting for a copy of a filed invoice to print to show the authorizing signatures and payment date, four times as fast is real nice!

Taking advantage of the latest IBM Publications. IBM has continued to redefine IPDS. You will note a little disclaimer in any manual which says words to the effect of, "We reserve the right to change any and all of these specifications at any time we feel like it". Well, IBM have. But as time goes by, the definition gets better and tighter.

Standardizing IPDS. IBM's definition of IPDS is very vague. A printer may be called IPDS capable if it supports a data transport method (twinax, coax, token ring, parallel) and any other tower of IPDS. Support for a tower is defined as "support for any part of the tower". With this definition, it is quite legal within this definition to support twinax communication, and only implement support for 10 character per inch portrait printing at 6 lines per inch in the PTOCA (Presentation Text Object Content Architecture) tower. In this way, a band printer could be called IPDS-capable!

Anzac does not use the IBM definitions to define Anzac's IPDS products. Rather, Anzac supports as a minimum all the capabilities of mainstream IBM printers to ensure that end users have no compatibility or functionality issues with the printers they are currently using.

Product Consistency. Some IBM lasers can address the entire page area. Some cannot. Some run at 240 dpi, some at 300 dpi. Some IBM matrix printers work at 144 by 144 dpi: others at 144 by 120 dpi. In the fine print, you will see the differences itemized, and the effect the differences will have on page presentation in the different towers. Problem is, with the massive complexity of IPDS (which can be compared to PostScript 2), it takes a rocket scientist in the printer area to determine whether these differences will have any impact on applications which will be implemented during the foreseeable life of the printer!

Anzac printers are absolutely consistent. At a base level, all Anzac lasers emulate the IBM 4028. All Anzac impact printers emulate the IBM 4224/4230. So the results on the printed page are identical for all matrix printers and all laser printers.

Error Messaging. In the IBM Manual "Intelligent Printer Data Stream, Data Stream and Object Architectures" (IBM publication number S544-3417-03), there is a comprehensive list of IPDS error messages. Literally, thousands of them. They diagnose the actual error based on the IPDS tower being used, and the error in data presentation within the tower.

IBM's current printers report back to the System when an error is encountered, and throw out the entire page. The cause for the error is then displayed on the console. IBM's older printers, with less discrimination, will often print the page.

To maintain consistency with both IBM's old and new printers, the Anzac printers print the error at the location on the page where the item should have been printed if presented correctly. This has two major advantages. First, instead of stopping and documenting the first IPDS error only, it documents every error on the page. This is very useful to programmers: instant diagnosis of all the IPDS programming errors. The second advantage: if you absolutely must have printout, the job will print. All Anzac printers print the error messages and continue. IBM printers simply will not print a print job that contains errors.

Support for past and present IBM IPDS implementations. There are bugs in early IBM products, which have been ironed out in later products. For example, the IBM 4224, when first released, would print bar codes which contained illegal characters. The bar code was unreadable by any bar code reader. Later versions of the 4224, and the current IBM 4230, simply stop dead on the same print job, issuing a console message. There is no override: the job will not print until the print program has been re-written. The Anzac approach is to execute the print job, but print the IBM error message where the invalid bar code would be. This user-friendly diagnostic still allows the print job to be printed, but also raises the alarm that the printer is being sent garbage, and a programmer should attend to the problem when they have the time. This solution is acceptable to owners of older IPDS printers as well as current IBM 4230 customers.

Field Upgradeability from SCS. Most Anzac printers can be field upgraded from the older SCS controllers to the new IPDS controller. Anzac is the only vendor in the marketplace that offers this feature. The IBM solution for those users who decide to implement IPDS is to purchase new IBM printers!

Transportability for future applications. The IPDS software interpreter is written in "C". This makes it rapidly transportable to any other hardware platform. (In other words, in ten years time when we want to update our hardware design, it will take less than twelve weeks to design the hardware and transport the software to the new hardware design).

Long term design. The entire hardware design of the Anzac IPDS controller can be characterized in one word: Overkill. Too much memory (two megabytes minimum: virtually no maximum). Too much horsepower. Too much everything. This is based on one of Murphy's laws, which says if you aint got it, you're gonna need it. The reason for designing in Overkill is the long term reduction of risk to the customer. Anzac has a reputation for building printers which last a very long time, and supporting those printers forever. Do not be surprised if star quadrants on the Enterprise are printed out on an Anzac IPDS laser.

Long term software design. The Anzac IPDS controller has been over-engineered from every angle. The hardware, as already outlined, is overkill. But the software development is even more interesting. There are 23 IPDS functions in the GOCA tower (Graphics Object Content Architecture) which are the maximum requirement for an IPDS printer to support. However, there are another 60 functions which are not currently used on printers, but would be used on screens. The Anzac software supports all these functions. If IBM ever include them as part of IPDS, then we will already support them.

IBM's IPDS Limitations. IBM has a published specification for IPDS. Every IBM printer supports a subset, or partial list, of the capabilities of IPDS. For example, IBM impact IPDS printers can only handle five overlays. The 4224 does not rotate images, or support imaging. IPDS is a work in progress. Extra features are still being added. While IPDS was announced in 1984, the specifications for G3/G4 fax compression/decompression were not determined until 1987 by CCITT. They became part of IPDS around 1990, with the release of the IBM 4028 laser, and were added into IBM's feature list in documentation released in 1991. IBM printers released prior to this date were not updated to support the new additions to IPDS functionality, and as a result still do not support these features today.

Anzac's IPDS implementation supports all towers to IBM's latest published specification. While we encourage programmers to stay within the confines of the IBM supported towers for the different printing technologies, it may be of interest to programmers that, as IBM add capability to their printers, the feature will already be supported by the Anzac printer. (Note: Imaging will be added to the Anzac matrix printers by March 31, 1995).

The result of IBM's differing implementation of IPDS in the different printers means that the original intent of IPDS (which was to produce the same image on the page, regardless of the printing technology used) has been lost in the shuffle.

In some cases, features are supported in the IBM printers, but the support is limited. For example, the IPDS specification permits any number of forms overlays to be sent to the printer and stored there. Any overlay, or combination of overlays, can be called up and printed at any time with a short, simple command. The IBM 4224 and 4230 are arbitrarily restricted to a maximum of 5 overlays (if you have the optional memory installed: 0.5 megabytes for $750!). The Anzac impact printers have no practical limitation on the number of overlays, and are delivered with 2 megabytes of memory, which is upgradable to 8 megabytes! This saves a lot of forms downloading and results in much faster print production.

The Anzac IPDS hardware is over-engineered for the current feature level of IPDS. The intention was to leave sufficient headroom in the hardware to permit long term software support of as-yet-unreleased IPDS enhancements. For the risk-averse customer, who wants a long term hardware strategy which avoids the kind of obsolescence caused by the introduction of a new data compression algorithm, (such as imaging!) Anzac has the perfect answer.


 

Anzac IPDS and the future.

The Anzac IPDS solution conforms to IBM's original design intentions in their Statements of Direction, and is the most likely future direction for IBM's own printers. It conforms to IBM's newest documented standards, offering a much more complete implementation of IPDS than IBM's own products, yet still supports printing today's print jobs in the same manner as IBM's current IPDS printers.

Maintenance is a large part of Anzac's business, which is a direct result of the success of Anzac's high speed System printers and durable desk top printers over the past 11 years. New Anzac products are engineered with long term maintenance and support considerations.

As a result, every aspect of Anzac's IPDS product has been over-engineered. While a more expensive solution in the short term, it is expected that the savings over the life of the printer will more than offset the higher initial cost.


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