Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!linus!security!genrad!decvax!harpo!seismo!hao!hplabs!sri-unix!Schauble.HIS_Guest@MIT-MULTICS From: Schauble.HIS_Guest%MIT-MULTICS@sri-unix.UUCP Newsgroups: net.micro.pc Subject: MS-DOS and 80188 Interrupt Vectors Message-ID: <13274@sri-arpa.UUCP> Date: Wed, 2-Nov-83 03:15:00 EST Article-I.D.: sri-arpa.13274 Posted: Wed Nov 2 03:15:00 1983 Date-Received: Sat, 5-Nov-83 20:51:48 EST Lines: 81 >From DTACK GROUNDED, The Journal of Simple 68000 systems. Subscriptions $15 for 10 issues to 1415 E McFadden, Ste F, Santa Ana, CA 92705. Reproduced with permission. ---------------------------------------------------------------------- There are a few chip designers and sellers at Intel (the rumor goes) who would like to shoot Bill Gates right now. It seems the Microsoft folks can't read, and as a result Intel has a large pile of 80188s it can't ship. And Intel is redesigning the 80188 chip. Again. It's like this: the 8088 spec sheet reserves two of the 256 jump vector addresses for future Intel use. Microsoft went ahead and used them in the MS-DOS operating system anyway. The large pile of 80188s that Intel can't ship use those two reserved vectors for a hardware purpose. Understand, now, Intel was right and Microsoft was wrong. And: true, Microsoft *could* modify MS-DOS to comply, retroactively, with Intel's entirely correct documentation. Unfortunately, there are about 12,000 application programs sitting on computer retailer's shelves all over the country which call those vectors... It would seem that in this case Intel's substantial software support backfired. Since Intel's documentation scrupulously documented that those two vectors are reserved, they are (the rumor goes) refusing to take back the 80188s it has sold, unless (the rumor continues) the customer uses a blue logo with three alphabetic characters. And now you know why peanut has not been shipped yet, and what CPU Peanut uses. We wonder how long it will take Intel to change the mask -- again -- and get the chip back into production -- again? (Do you realize that most folks don't know why Peanut hasn't been released but YOU do?) And you also know why the Intel folks would like to shoot Bill Gates. (If the rumor is correct.) HERE ARE THE FACTS The following information was gathered from the Intel iAPX86/88, 186/188 User's Manual, Intel 210912-001, pages 4-10 and 5-5; and from the IBM PC XT Technical Reference Manual, page 2-4. Page 4-10 shows that thae 8088 has 5 (five) dedicated interrupt pointers 0-4), 27 reserved interrupt pointers 5-31), and 224 (user) available interrupt pointers 32-255). Page 2-4 of the IM manual reveals that MS-DOS uses 25 of those 27 reserved interrupt vectors. Specifically, MS-DOS uses 5 and 8 through 31 inclusive. Now turn to page 5-6 of the Intel manual. Table 5-2 reveals that the 80186/88; uses 5 as a vector for the array bounds exception, and also vectors 6 thru 15 and 18 and 19. Which means that MS-DOS programs will *NOT*, in general, run on the 80186/8. We are told that the better the program, the more likely that those MS-DOS vectors are being used at the application level. The fact is that the 80186/8 is a very cost-effective chip at the hardware system level, as we have reported before. It is highly logical that IBM would, given enough lead time, use the 80188 in a highly cost-sensitive device such as a home computer. Let us assume that this tiny, trifling conflict was discovered very late in the design cycle for Peanut (in large companies, the hardware and software types sometimes don't communicate well). We can think of four ways out of the dilemma: 1) Cancel Peanut. 2) Go to market with a product that won't run all those MS-DOS based PC programs out there. 3) Re-design Peanut to use the 8088 - an expensive and time-consuming alternative involving a complete re-layout of the main circuit board. 4) Get the company which you own a large piece of to take back all those 188 chips IBM (may) have bought and *re-design the 188 to conform to MS-DOS*. This is *also* time consuming but the expense is placed elsewhere. We would like to thank Otherwise Intelligent for the rumor and Harry S, who is affiliated with a networking firm, for his help in piecing the facts together.