cramer@kontron.UUCP (Clayton Cramer) (01/20/86)
About three weeks ago, the power supply on my antique (16K RAM chips on the motherboard) IBM PC broke. In the process of replacing it, SOMETHING happened to it, with the result that it powered up with two long beeps and one short one (or something like that). According to the Guide to Operations manual, this indicated a problem with the System Unit (please take to your local repair facility and surrender your wallet). Of course, I assumed that something had been damaged on the motherboard, perhaps because of the power supply failure. Fortunately, Kontron Electronics makes logic analyzers, and we have lots of neat test equipment around (that's our business), and after several hours of studying the signals on the backplane and the display controller card, my colleague Brad said, "Gee, it looks like it's trying to write to the color monitor memory." At which point I said, "Gee, I wonder if the DIP switch on the motherboard that selects the monitor got altered." You see, on the PC this particular DIP switch is right next to the plugs for the motherboard power supply. (On the XT, it's quite a ways away.) Of course, this was the case. Why, oh why, couldn't IBM make the BIOS smart enough to distinguish "wrong or missing display adapter" from "system unit error"? At least I didn't end up buying a new motherboard.