ROM debuggers (was Re: PDP-11/44 boot prompt)

1. Combination and degree. If one person claims that all X have Y, and then you claim that not all X have Y (= no X have Y (which we agree is false in this case) or some X don't have Y (which is in dispute)) immediately afterward without giving evidence, that doesn't have the same effect as making your claim first. Also, your claim is totally opposite from the previous claim (that's what I meant by "degree"). So if you want me to believe you, sub- stantiation is nice. Also, you wrote "certainly". That just makes a naked claim even less appealing to me. 2. Prejudice. I read your argument and wanted to counter it right away. ("Hmph! Is he thinking that old Macs don't have ROM debuggers? That's not true in my experience. Is he thinking that new Macs don't have ROM debuggers? That's also not true -- I *know* the iMac has Open Firmware, for example.") 3. Proving your claim. Unless you've disassembled the ROMs, you don't *know* there isn't a debugger in there. If I claim there *is*, I may be able to show it to you easily. Yes. I asked you because of reason 4: I think you're at least partially wrong. This I doubt. You could be right (especially in the case of the Performas) which I will admit if it's true. No. Many of the older models had a plastic switch that snapped into the ventilation slots; it would reset the machine or bring up a debugger. I vaguely remember using the SE's debugger to look at a picture of the development team that was hidden in ROM. And as it turns out, Apple has a Tech Note (#1136) on the subject. (I vaguely remembered it before reading your post; afterward I went and looked it up. So I'm not trying to be *too* unkind or to have all the evidence beforehand and bait you.) It says: About MicroBug MicroBug was first introduced with the Mac Plus and has been a standard component in the ROM of all Mac OS computers since then. MicroBug is invoked when the system takes a Non-Maskable Interrupt (NMI) and there is no other debugger (e.g., MacsBug) installed. MicroBug is not present on the Macintosh 128, Macintosh 512, and Macintosh XL computers. So you're right about the 128, 512, and XL, but wrong about the Plus, SE, II, IIx, and IIcx. I just saw the debugger on my 7100/66 the other day when I hit Cmd-Shift-Power instead of Cmd-Ctrl-Power. I doubt it's been updated to handle the PPC. I know many newer machines have Open Firmware (hold down Cmd-Opt-O-F when turning on -- the letter O, not zero) which could be used for debugging, if you're evil and know FORTH. :) I'm not going to reboot my machine while I'm writing this message! So I could be wrong but I doubt it. -- Derek