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Comment by w10-1 | Hacker News Reader

Interesting: ROM code was accessed through ANNN ("A-line") traps. Then they started using F-line traps for co-processors. Then in the proliferation of models targeting education, they started putting out advanced CPU's without co-processors, so lots of software crashed expecting a co-processor. But of course if Word crashed, they'd talk about monkey-patching the OS pending the next release. Apple folks thought MS tailored their software to break the Mac, and thereby gain the upper hand in licensing talks.

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As a programmer writing OS-level utility software for Macs back in the day, I stumbled across one of the MS-preservation hacks in Mac OS. I wrote about it here on Hacker News twelve years ago:

https://news.ycombinator.com/item?id=5322639

For your convenience, I'll quote the most relevant part of the story:

> One day, I was tracing through the OS code that handled a context switch and was surprised to find a bit of code that looked up the 32-bit creator code of the current application and compared it to 'WORD'. What the heck is this? I wondered. Turns out it was a hack added by the OS engineers at Apple to keep some other hacks in Microsoft Word working. If I recall correctly, they had to determine if Word was getting switched in or out so they could enable or disable the necessary hacks. So, in effect, they had a hack that would live-hack the OS to add hacks for Word's hacks and then live-unhack the hacks for everything else.

> I mean, when you're hacking the system to hack the system on behalf of someone who already hacked the system but for an older version of the system that's no longer there, now you're doing some hacking.

Is this an AI response? It's essentially gibberish after the first two sentences.

It all makes sense to me v(._. )v

https://vintageapple.org/inside_o/pdf/Inside_Macintosh_Volum...

“Calls to the Toolbox and Operating System via the trap dispatch table are implemented by means of the MC68000's "1010 emulator" trap. To issue such a call in assembly language, you use one of the trap macros defined in the macro files. When you assemble your program, the macro generates a trap word in the machine-language code. A trap word always begins with the hexadecimal digit $A (binary 1010); the rest of the word identifies the routine you're calling, along with some additional information pertaining to the call.”

It is written very strangely. It's not exactly like they reached the decision to use F-line traps for co-processors, I'm pretty sure F-line traps were designated by Motorola for co-processors, and A-line traps were free for use for OS and Toolbox trap instructions.

The "software crashed expecting a co-processor" part doesn't make any sense either, you were always supposed to check if a co-processor was available. There was no big rug pull or anything, both the first models and some later models simply did not have co-processors. Developers were provided this information.

And the last two sentences seem completely unrelated to the prior ones, so I'm not really sure what they're trying to string together.

It mostly makes sense to me. "Advanced CPUs" should have been "advanced models" (The Mac LC) missing coprocessors.

And it probably was true that crashes in Microsoft products got patched in the system, while most other app developers did not get that courtesy.

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