tedj@hpcilzb.UUCP (12/03/87)
Has anyone seen the article on p22 of the Dec. '87 IEEE "Spectrum"? Supposedly it is possible for a buggy program to burn out a flyback transformer?!? The example they give is with an IBM PC..., is this a problem with a Mac SE HD20 also? I have crashed my SE pretty hard while debugging some LSC programs (e.g., the bomb box doesn't show up, but the screen gets spastic and starts making loud noises). Am I treading on dangerous ground here? -Ted ********************************************* Ted Johnson Hewlett-Packard, Design Technology Center Santa Clara, CA (408)553-3555 UUCP: ...hplabs!hpcea!hpcilzb!tedj *********************************************
oster@dewey.soe.berkeley.edu (David Phillip Oster) (12/05/87)
In article <870057@hpcilzb.HP.COM> tedj@hpcilzb.HP.COM (Ted Johnson) writes: >Has anyone seen the article on p22 of the Dec. '87 IEEE "Spectrum"? >Supposedly it is possible for a buggy program to burn out a flyback >transformer?!? The example they give is with an IBM PC..., is this >a problem with a Mac SE HD20 also? I've known this since a few months after the IBM was released: The ultimate copy protection: "This is an illegal copy. Now erasing copy. Now erasing hard disk. Now setting fire to your monitor. It is a crime to steal software. Thank you for your support." This flaw in the design of IBM video was discovered by some early screen-savers that darkened the screen by reprogramming the video controller chip. It was reported in the literature about 1 year after the IBM PC was released. The way it works is: An IBM PC CGA or Monchrome video card supports both 80 chars per line and 40 chars per line video modes, and it lets you adjust the left margin of the picture in software. (This was so the picture could be shown on your home TV set.) This means there is a lot of software control over the exact shape of the video waveform. Some waveforms can cause the high voltage transformer (the flyback transformer) to catch fire on some monitors. It takes a while for the transformer to heat hot enough to really damage itself, so if you are quick, you can keep yourself safe. A mac, fat mac, macPlus, or SE does not provide as much control over the waveform, so you should be safe. One exception: I have crashed the machine so bad that I've lost horizontal synch. (Symptom: a dim screen with a patterns of bright, almost horizontal lines (at 25 degree) on the screen. If you see this, reboot immediately!) There is all kinds of bizarre stuff in the standard board for the II. (For example, did you know that Apple's video board for the Mac II supports smooth scrolling?) So, be careful. All of this was discussed a few months ago in comp.misc, in a discussion on exploding computers. (The famed HaltAndCatchFire instruction on some early IBM mainframes is another good example. This one was supposed to set a block of memory to zero, but if you only had a partly-populated memory board, and you tried to clear a lot of it, the amps would send out so much juice that the core memory caught fire.) Along the same lines, it is possible to write a set of boot blocks for the Mac II that appear to boot normally, then power down the machine before you can actually do anything. I have a BSR-X10 power control system hooked to my Mac, but I don't let it control its own power for just that reason. Though, I really don't worry about damage to my hardware. I worry about damage to my data. Since I write for a living, my data is much more valuable than my hardware. If you are doing application programming, don't worry about this sort of thing. My experience has been that you are unlikely to trigger something disasterous unless you are writing near a danger area. For example, there is a SCSI command: EraseHardDisk, but if you access your hard disk through the File Manager, you are unlikely to write a bug that sends that command. --- David Phillip Oster --A Sun 3/50 makes a poor Macintosh II. Arpa: oster@dewey.soe.berkeley.edu --A Macintosh II makes a poor Sun 3/60. Uucp: {uwvax,decvax,ihnp4}!ucbvax!oster%dewey.soe.berkeley.edu
tedj@hpcilzb.HP.COM (Ted Johnson) (12/08/87)
/ hpcilzb:comp.sys.mac / oster@dewey.soe.berkeley.edu (David Phillip Oster) / 8:34 am Dec 5, 1987 / In article <870057@hpcilzb.HP.COM> tedj@hpcilzb.HP.COM (Ted Johnson) writes: >A mac, fat mac, macPlus, or SE does not provide as much control over the >waveform, so you should be safe. One exception: I have crashed the machine >so bad that I've lost horizontal synch. (Symptom: a dim screen with a patterns >of bright, almost horizontal lines (at 25 degree) on the screen. If you see >this, reboot immediately!) [stuff deleted...] >If you are doing application programming, don't worry about this sort of >thing. My experience has been that you are unlikely to trigger something >disasterous unless you are writing near a danger area. For example, [stuff deleted...] Couldn't ANY bug (e.g., a function call with the wrong type of argument) which does a write turn out to be a pathological monster and write near a danger area? -Ted
edwards@bgsuvax.UUCP (Bruce Edwards) (12/12/87)
Only to your mental health.......just because you're paranoid
doesn't mean their not really after you.........
:-)
'These are only the shadowlands.' C.S. Lewis
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