mslater@cup.portal.com (Michael MPR Slater) (10/18/88)
The following article is excerpted with permission from the Microprocessor Report newsletter. One of the surprises IBM dropped on the PC community earlier this year was that they expected patent royalties on PC and AT compatible systems, as well as on Micro Channel systems. Press reports indicated that IBM was circulating a list of about 20 representative patents, but the only patent that was publicly identified was the so-called Christiansen patent, number 3,812,475. This massive 1974 patent covers virtually any computer system with a DMA controller. We have located nine patents, listed below, that are specifically related to IBM's PC and AT designs. After a brief review of these patents, we suspect that all IBM-compatible personal computers violate several of them, and we find it surprising that IBM has not been more aggressive in seeking royalties from makers of such machines. Perhaps the explanation is, in part, that most of the larger suppliers have blanket cross-license agreements with IBM, and the smaller ones aren't worth IBM's trouble. IBM is also likely to move cautiously to avoid any possible anti-trust claims. ----------------------------------------------------------- 4,437,093, applied for 8/12/81, granted 3/13/84: Apparatus and method for scrolling text and graphic data in selected portions of a graphic display 4,460,957, applied for 8/12/81, granted 7/17/84: Self-pacing serial keyboard interface for data processing system 4,509,113, applied for 2/2/82, granted 4/2/85: Peripheral interface adapter circuit for use in I/O controller card having multiple mode of operation 4,528,626, applied for 3/19/84, granted 7/9/85: Microcomputer system with bus control means for peripheral processing devices 4,570,161, applied for 8/16/83, granted 2/11/86: Raster scan digital display system 4,575,826, applied for 2/27/84, granted 3/11/86: Refresh generator system for a dynamic memory 4,580,135, applied for 8/12/83, granted 4/1/86: Raster scan display system 4,598,356, applied for 12/30/83, granted 7/1/86: Data processing system including a main processor and a co-processor and co-processor error handling logic Re. 32,201, applied for 8/6/84, granted 7/8/86: Apparatus and method for reading and writing text characters in a graphics display (Reissue of patent 4,408,200, applied for 8/12/81 and granted 10/4/83) ----------------------------------------------------------- An effort is now underway by several manufacturers of PC compatibles to raise a challenge to these patents. The strongest challenge would be based on the existence of prior art; a more difficult approach is to question whether the patented techniques would have been obvious to someone skilled in the field at the time the patents were issued. Several of the patents seem to have broad applicability. The patent "Raster scan display system" (4,580,135) appears to cover any display controller with both bit-mapped and character-oriented modes, if it uses a memory whose contents can be interpreted either as a bit-map (to be displayed directly) or as character codes (to be used as inputs to a character generator memory). All display adapters with CGA compatibility (including EGA and VGA adapters) appear to be covered by this patent. The patent "Self-pacing keyboard interface..." (4,460,957) covers the bidirectional serial interface used in the PC, and any PC compatible that uses the standard interface will likely violate the patent. Patent 4,598,356 covers the connection of the error signal from the 287 to the 286 in an AT-compatible system. While it should be possible to modify the design to avoid this patent, any design that simply mimics IBM's approach (as most do) will surely violate the patent. Another patent of concern to all AT makers is "Microcomputer system with bus control means ..." (4,528,626), which covers the bus's master mode operation. You can order patents from the U.S Patent and Trademark Office, Washington, DC 20231; the cost is only $1.50 each, but delivery takes 1 to 2 months. You can also copy them from the patent library in Sunnyvale, CA, or from other patent libraries around the country. Microprocessor Report will provide a bound set of these nine patents for $40 postpaid, plus $2.80 tax in California. We also have available a set of 16 recent IBM RISC patents, as posted on the net by Allen Baum, for $50, plus $3.50 tax in California. (Outside U.S. and Canada add $20 for each set for airmail postage.) Send a check or credit card information to MicroDesign Resources Inc., 550 California Ave., Suite 320, Palo Alto, CA 94306, or call 415/494-2677, or send email to mslater@cup.portal.com.