November 1995 


Almost Like An Old Friend...

Print Error 21: An Error For Every PC

THE MOST COMMON error messages in the entire PC world may be the cryptic “20 Mem Overflow” and “21 Print Overrun.”

Perhaps you know them? They are found with machines running MS-DOS, Windows 3.x, Windows 95, and OS/2, and are most likely to occur when printing to the most popular lasers, especially the Hewlett Packard LaserJet III and 4.

Both are related to the memory installed (or more precisely not installed) in the printer, and the method the printed page is assembled by the computer and printer. And interestingly, they have been perpetuated by some of the niftiest advances in LaserJet technology.

Here’s the deal. In HPGL/2 mode, the Hewlett Packard LaserJet III and 4 create images internally, which cuts down on data transfer to the printer and can therefore improve printing speed.

Because HPGL/2 is vector based, it defines curves using a recursive algorithm which generates many short lines. Trying to print a simple circle in Microsoft Publisher running under either Windows or OS/2, for instance, can result in a LaserJet generating thousands of these lines, and sapping printer resources.

Another advance of HPGL/2 is that it allows images to be composed at 600 dpi rather than the 300 dpi formerly attained by LaserJets. This produces noticeably better output in most cases, but requires four times as much memory to produce the same page at 300 dpi.

So if you’re hit by one of the “twenty-something errors,” Henna Gaijin described them in CorelDraw Journal, the first thing to do is to see whether you have Page Protection enabled on your printer (it should be accessible through the Windows Control Panel / Printers / Setup).

If Page Protection is enabled, the printer will try to compose the entire page internally, which can lead to 20 Mem Overflow errors. If you disable Page Protection, the computer will help process the page for the printer, but if the computer can’t supply the printer quickly enough (as is most likely to be true with large, memory intensive jobs), you’ll get a 21 Print Overrun error.

Talk about being caught between a rock and a hard place! Here are a few more things you can try:

  1. Reduce the printer resolution to 300 or even 150 dpi.
  2. Reduce the size and resolution of any images contained in the problematic page (i.e., resample them or convert TIF images to JPG, which generally produces smaller files).
  3. Switch from HPGL/2 to raster mode (this is not possible on all LaserJets). Raster mode interprets the page as a bitmap rather than a vector image, and is therefore much less demanding on memory.
  4. Print the page as Postscript (if you have both Postscript and PCL available on your printer).
  5. If you are using a LaserJet 4 or 5, you can try using the LaserJet III driver.
    If one of these gets you through the briar patch, great. If not, you’re not alone. This problem is an equal opportunity afflicter, and frankly there is really only one cure: add more RAM to your printer and/or get a more powerful PC.


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