Editing IBM PC compatible (section)

==="Operationally Compatible"===
{{quote|The first thing to think about when considering an IBM-compatible computer is, "How compatible is it?"|''BYTE'', September 1983{{r|malloy198309}}}}

In May 1983, Future Computing defined four levels of compatibility:<ref name="ward198311">{{cite news | url=https://archive.org/stream/byte-magazine-1983-11/1983_11_BYTE_08-11_Inside_the_IBM_PC#page/n249/mode/2up | title=Levels of PC Compatibility | work=BYTE | date=November 1983 | access-date=March 19, 2016 | author=Ward, Ronnie | pages=248–249}}</ref>

* ''Operationally Compatible''. Can run "the top selling" IBM PC software, use PC expansion boards, and read and write PC disks. Has "complementary features" like portability or lower price that distinguish computer from the PC, which is sold in the same store. Examples: (Best) Columbia Data Products, Compaq; (Better) Corona; (Good) Eagle.
* ''Functionally Compatible''. Runs own version of popular PC software. Cannot use PC expansion boards but can read and write PC disks. Cannot become Operationally Compatible. Example: [[Texas Instruments Professional Computer and Professional Portable Computer|TI Professional]].
* ''Data Compatible''. May not run top PC software. Can read and/or write PC disks. Can become Functionally Compatible. Examples: NCR Decision Mate, [[Olivetti M20]], Wang PC, [[Zenith Z-100]].
* ''Incompatible''. Cannot read PC disks. Can become Data Compatible. Examples: [[Altos 586]], [[Rainbow 100|DEC Rainbow 100]], [[Grid Compass]], [[Victor 9000]].

[[File:Compaq mddos ver1-12.jpg|thumb|right|MS-DOS version 1.12 for Compaq Personal Computers]]

During development, Compaq engineers found that ''[[Microsoft Flight Simulator]]'' would not run because of what [[subLOGIC]]'s [[Bruce Artwick]] described as "a bug in one of Intel's chips", forcing them to make their new computer [[bug compatibility|bug compatible]] with the IBM PC.{{r|yakal198501}} At first, few clones other than Compaq's offered truly full compatibility.<ref name="alsop19940131">{{cite magazine |url=https://books.google.com/books?id=AzsEAAAAMBAJ&pg=PT1 | title=A public Windows pane to make compatibility clearer | access-date=February 28, 2011 | author=Alsop, Stewart | date=January 31, 1994 | magazine=InfoWorld | pages=102}}</ref> [[Jerry Pournelle]] purchased an IBM PC in mid-1983, "[[Model F keyboard|rotten keyboard]] and all", because he had "four cubic feet of unevaluated software, much of which won't run on anything but an IBM PC. Although a lot of machines claim to be 100 percent IBM PC compatible, I've yet to have one arrive ... Alas, a lot of stuff doesn't run with Eagle, Z-100, [[Compupro]], or anything else we have around here".<ref name="pournelle198309">{{Cite magazine |last=Pournelle |first=Jerry |author-link=Jerry Pournelle |date=September 1983 |title=Eagles, Text Editors, New Compilers, and Much More |url=https://archive.org/details/byte-magazine-1983-09 |magazine=BYTE |page=[https://archive.org/details/byte-magazine-1983-09/page/n322 307] |access-date=April 7, 2019}}</ref> Columbia Data Products's November 1983 sales brochure stated that during tests with retail-purchased computers in October 1983, its own and Compaq's products were compatible with all tested PC software, while Corona and Eagle's were less compatible.<ref name="cdp198311">{{Cite book |url=https://archive.org/details/1983-columbia-eval/mode/1up |title=IBM PC Compatibles Competitive Evaluation |year=1983 |publisher=Columbia Data Products |publication-date=November 1983 |access-date=October 15, 2022}}</ref> [[Columbia University]] reported in January 1984 that [[Kermit (protocol)|Kermit]] ran without modification on Compaq and Columbia Data Products clones, but not on those from Eagle or Seequa. Other MS-DOS computers also required custom code.<ref name="dacruz19840123">{{Cite mailing list |last=da Cruz |first=Frank |title=IBM PC Kermit |mailing-list=Info-Kermit Digest |date=January 23, 1984 |url=https://www.columbia.edu/kermit/ftp/e/mail.84a |access-date=2024-10-12 |publisher=Kermit Project, Columbia University}}</ref>

By December 1983 Future Computing stated that companies like Compaq, Columbia Data Products, and Corona that emphasized IBM PC compatibility had been successful, while non-compatible computers had hurt the reputations of others like TI and DEC despite superior technology. At a San Francisco meeting it warned 200 attendees, from many American and foreign computer companies as well as IBM itself, to "Jump on the IBM PC-compatible bandwagon—quickly, and as compatibly as possible".<ref name="sandler198312">{{Cite magazine |last=Sandler |first=Corey |date=December 1983 |title=The Prognosticators Pronounce: Future Compilations On The PC |url=https://books.google.com/books?id=05wAGZQlo9QC&pg=PA248 |magazine=PC Magazine |pages=248–256 |access-date=2023-12-27}}</ref> Future Computing said in February 1984 that some computers were "press-release compatible", exaggerating their actual compatibility with the IBM PC.<ref name="salisbury19840209">{{Cite news |last=Salisbury |first=David F. |date=February 9, 1984 |title=Why the IBM PC spawned a mob of look-alikes |work=The Christian Science Monitor|url=https://www.csmonitor.com/1984/0209/020908.html |access-date=October 7, 2020 |issn=0882-7729}}</ref> Many companies were reluctant to have their products' PC compatibility tested. When ''PC Magazine'' requested samples from computer manufacturers that claimed to produce compatibles for an April 1984 review, 14 of 31 declined.<ref name="krasnoff19840320">{{cite news |url=https://books.google.com/books?id=1tFFnOMCvv4C&pg=PA57 | title=No Matter Who's Invited, Some Will Turn Out To Be Incompatible | work=PC Magazine | date=March 20, 1984 | access-date=October 24, 2013 | author=Krasnoff, Barbara | pages=57}}</ref><ref name="krasnoff19840403">{{cite news |url=https://books.google.com/books?id=e-gI2W-3JwkC&pg=PA110 | title=Putting PC Compatibles To the Test | work=PC Magazine | date=April 3, 1984 | access-date=October 24, 2013 | author=Krasnoff, Barbara | pages=110–144}}</ref> Corona specified that "Our systems run all software that conforms to IBM PC programming standards. And the most popular software does."<ref name="corona19840227">{{cite news | url=https://books.google.com/books?id=gy4EAAAAMBAJ&pg=PA41 | title=Pick Up Where IBM Leaves Off. | work=InfoWorld | date=February 27, 1984 | access-date=January 18, 2015 | pages=41 | type=advertisement}}</ref> When a ''[[BYTE]]'' journalist asked to test [[Peachtext]] at the Spring 1983 [[COMDEX]], Corona representatives "hemmed and hawed a bit, but they finally led me ... off in the corner where no one would see it should it fail". The magazine reported that "Their hesitancy was unnecessary. The disk booted up without a problem".<ref name="malloy198309">{{cite news | url=https://archive.org/stream/byte-magazine-1983-09/1983_09_BYTE_08-09_Portable_Computers_in_Depth#page/n235/mode/2up | title=The Corona Portable PC | work=BYTE | date=September 1983 | access-date=August 16, 2015 | author=Malloy, Rich | pages=226–228}}</ref> [[Zenith Data Systems]] was bolder, bragging that its Z-150 ran all applications people brought to test with at the 1984 [[West Coast Computer Faire]].{{r|pournelle198407}}

''[[Creative Computing]]'' in 1985 stated, "we reiterate our standard line regarding the IBM PC compatibles: try the package you want to use before you buy the computer."{{r|lockwood198509}} Companies modified their computers' BIOS to work with newly discovered incompatible applications,<ref name="pournelle198411">{{cite news |url=https://archive.org/stream/byte-magazine-1984-11/1984_11_BYTE_09-12_New_Chips#page/n359/mode/2up | title=NCC Reflections | work=BYTE | date=November 1984 | access-date=October 23, 2013 | author=Pournelle, Jerry | pages=361}}</ref> and reviewers and users developed [[Stress testing (software)|stress tests]] to measure compatibility; by 1984 the ability to operate Lotus 1-2-3 and ''Flight Simulator'' became the standard,<ref name="mace19840109_16">{{cite news | url=https://books.google.com/books?id=ey4EAAAAMBAJ&pg=PA79 | title=IBM PC clone makers shun total compatibility | work=InfoWorld | date=January 9–16, 1984 | access-date=February 4, 2015 | author=Mace, Scott | pages=79–81}}</ref><ref name="poor19841002">{{cite news |url=https://books.google.com/books?id=d-tPdHcBE9wC&pg=PA206 | title=Zenith Strikes Twice | work=PC Magazine | date=October 2, 1984 | access-date=October 25, 2013 | author=Poor, Alfred | pages=206}}</ref>{{r|pournelle198411}}<ref name="callamaras198411">{{cite news |url=https://archive.org/stream/byte-magazine-1984-11/1984_11_BYTE_09-12_New_Chips#page/n273/mode/2up | title=The Columbia Multipersonal Computer-VP | work=BYTE | date=November 1984 | access-date=October 23, 2013 | author=Callamaras, Peter V. | pages=276}}</ref><ref name="lockwood198509">{{cite news |url=http://www.atarimagazines.com/creative/v11n9/50_Zenith_Z151_choice_of_U.php | title=Zenith Z-151; choice of U.S. Air Force and Navy | work=Creative Computing | date=September 1985 | access-date=February 26, 2013 | author=Lockwood, Russ | pages=50}}</ref><ref name="mace19860505">{{cite magazine |url=https://books.google.com/books?id=Qi8EAAAAMBAJ&q=%22flight+simulator%22&pg=PA5 | title=Amiga, Atari Ready PC Emulators | access-date=February 28, 2011 |author1=Mace, Scott |author2=Karen Sorensen | date=May 5, 1986 | magazine=InfoWorld | pages=5}}</ref> with compatibles specifically designed to run them<ref name="pournelle198407">{{Cite magazine |last=Pournelle, Jerry |author-link=Jerry Pournelle |date=July 1984 |title=The West Coast Faire |url=http://blog.modernmechanix.com/the-west-coast-faire/ |magazine=[[Byte (magazine)|Byte]] |page=136 |access-date=November 8, 2011 |archive-date=May 28, 2012 |archive-url=https://web.archive.org/web/20120528184149/http://blog.modernmechanix.com/the-west-coast-faire/ |url-status=dead }}</ref><ref name="yakal198501">{{cite news | url=https://archive.org/stream/1985-01-computegazette/Compute_Gazette_Issue_19_1985_Jan#page/n33/mode/2up | title=Bruce Artwick / The Designer Behind Flight Simulator II | work=Compute!'s Gazette | date=January 1985 | access-date=July 6, 2014 | author=Yakal, Kathy | pages=32}}</ref> and prominently advertising their compatibility.<ref name="trivette198504">{{cite news |url=http://www.atarimagazines.com/compute/issue59/review_lotus_123.php |title=Lotus 1-2-3 For IBM PCjr |work=[[Compute!]] |date=April 1985 |access-date=2013-10-06 |author-last=Trivette |author-first=Donald B. |pages=63}}</ref>

IBM believed that some companies such as Eagle, Corona, and Handwell infringed on its copyright, and after ''[[Apple Computer, Inc. v. Franklin Computer Corp.]]'' successfully forced the clone makers to stop using the BIOS. The [[Phoenix Technologies|Phoenix BIOS]] in 1984, however, and similar products such as [[American Megatrends|AMI BIOS]], permitted computer makers to legally build essentially 100%-compatible clones without having to reverse-engineer the PC BIOS themselves.<ref name="caruso19840227">{{cite news | url=https://books.google.com/books?id=gy4EAAAAMBAJ&pg=PA15 | title=IBM wins disputes over PC copyrights | work=InfoWorld | date=February 27, 1984 | access-date=January 18, 2015 | author=Caruso, Denise | pages=15}}</ref><ref name="langdell19840710">{{cite news | url=https://books.google.com/books?id=Bwng8NJ5fesC&pg=PA56 | title=Phoenix Says Its BIOS May Foil IBM's Lawsuits | work=PC Magazine | date=July 10, 1984 | access-date=October 25, 2013 | author=Langdell, James | pages=56}}</ref><ref name="schmidt199407">{{cite news|url=http://www.smartcomputing.com/editorial/article.asp?article=articles%2F1994%2Fjuly94%2Fpcn0713%2Fpcn0713.asp |title=What Is The BIOS? |work=Computing Basics |date=July 1994 |author=Schmidt, Robert | access-date=September 19, 2011 | archive-url=https://web.archive.org/web/20120310002756/http://www.smartcomputing.com/editorial/article.asp?article=articles%2F1994%2Fjuly94%2Fpcn0713%2Fpcn0713.asp | archive-date=March 10, 2012}}</ref> A September 1985 ''[[InfoWorld]]'' chart listed seven compatibles with {{val|256|u=KB}} RAM, two disk drives, and monochrome monitors for {{US$|long=no|1495}} to {{US$|long=no|2320}}, while the equivalent IBM PC cost {{US$|long=no|2820}}.<ref name="iw19850930">{{cite news | url=https://books.google.com/books?id=iS8EAAAAMBAJ&pg=PA1 | title=Competing on Price | work=InfoWorld | date=September 30, 1985 | access-date=February 20, 2015 | pages=1}}</ref> The Zenith Z-150{{r|poor19841002}} and inexpensive [[Leading Edge Model D]] are even compatible with IBM proprietary diagnostic software, unlike the Compaq Portable.<ref name="freeze19851216">{{cite news | url=https://books.google.com/books?id=cC8EAAAAMBAJ&pg=PA43 | title=Leading Edge: Superior Value in IBM-PC Clone Market Contest | work=InfoWorld | date=December 16, 1985 | access-date=July 22, 2014 | author=Freeze, Ken | pages=43}}</ref> By 1986 ''[[Compute!]]'' stated that "clones are generally reliable and about 99 percent compatible",<ref name="halfhill198612">{{cite news | url=https://archive.org/stream/1986-12-compute-magazine/Compute_Issue_079_1986_Dec#page/n33/mode/2up | title=The MS-DOS Invasion / IBM Compatibles Are Coming Home | work=Compute! | date=December 1986 | access-date=November 9, 2013 | author=Halfhill, Tom R. |page=32}}</ref> and a 1987 survey in the magazine of the clone industry did not mention software compatibility, stating that "PC by now has come to stand for a computer capable of running programs that are managed by MS-DOS".<ref name=ferrell198707>{{Cite magazine |last=Ferrell |first=Keith |date=July 1987 |title=IBM Compatibles: The Universe Expands |url=https://www.atarimagazines.com/compute/issue86/007_1_IBM_Compatibles.php |magazine=Compute! |page=14 |access-date=January 31, 2020}}</ref>