Search results

I haven't had a chance to mess with the funky instruction any more, but I have a plan for verifying 100% that it's also happening on hardware. I bought a Classic II. There weren't any pics of the inside, and it was pretty ugly on the outside, but luckily it was not battery bombed. In fact, I'd...

I think that's a good way to put it! I wonder if you could use that header in conjunction with one of the actual NuBus slots to make a crazy frankenstein NuBus card that brings out the extra NuBus slots somehow (externally to another enclosure or something?). It looks like the only thing unique...

Ah, interesting! I was too blind to find it myself in the Bomarc schematics. The AI assistant in Adobe Reader was completely useless, too: So instead, I used @max1zzz's IIcx reloaded board file to trace out where they go, and sure enough, there it is in the Bomarc schematics. It's hooked up...

Interesting! Here's the Apple TIL article about it. Doesn't add any new knowledge, but thought I'd link it for completeness!

Definitely -- it originally came bundled with this model. I used to love playing Mario Teaches Typing both at home and at school! Speaking of bundled software, I know that my family's caddy-loading Performa 550 also came with Monopoly, but this restore CD didn't include it. The restore CD was...

I don't see any interaction with D1 at all. D2 is definitely what it grabs from to write to A4+4 sometimes, so it's likely the update operand. But I'm not seeing the behavior depend on what I have in D1 at all. With this setup: PC=0x2A036, random RAM location where I can put instructions. D0-D7...

Ahh, got it. Thanks! I feel like I'm not totally seeing that exact result. It matches what I'm seeing on test 2 with the 0x6500 from D2, but what about test 1 where A4+4 is 0 and D1 is not 0? It's not writing 0x6500 to A4+4 in that case. Either way, knowing what I'm looking for, I might do some...

This time I decided to play around with my LC III, and I think you may be onto something here on both counts. I know that the LC III has ROM mapped at 0x40800000 instead of 0x40A00000, but I left the register setup the same as what we see on the Classic II just for fun, except for the program...

I wondered about that too, but I can even set all the registers except A1 and A7 to 0, and I still get the same resulting A1 value on the IIci. I wonder if it's some kind of absolute address that it's grabbing? That's an interesting point! I wonder if it would be possible to make something...

I just thought of another test I could try with my IIci, since I have all kinds of programmable ROM SIMMs. I programmed a ROM SIMM so that the Classic II ROM is after the IIci ROM, mapped at 0x40A00000 just like it would be on hardware on the Classic II, so I can jump to the exact same address...

That's a great point. I think for the purposes of this code it won't matter because the weird behavior of the invalid instruction will likely put a good RAM address into A1 which will succeed in both 24-bit and 32-bit modes, but it would still be good to test in 32-bit mode as well for...

Thanks! It looks like you've confirmed that what we see on MAME really happens on hardware too with how it loaded 0x11 (becoming 0x22) into D0 and jumped out of bounds in the table to that incorrect CAS.W instruction. When I step through the ROM in MAME, A1 ends up with the value FFFF8FBA right...

Yep, I spent way too much time tracing my way through how it all works and comparing it against the SuperMario sources. I really wanted to find a simpler answer than what I've concluded above :D. Here are the relevant table entries from the universal tables in the Classic II ROM: The...

That's what I've been doing -- I tested the bad CAS instruction in MacsBug in both my LC II and my IIci. The more the merrier though if you want to test the CAS instruction and see if you can reproduce what I'm seeing! If you just put the following bytes in memory somewhere and set your PC to...

Thank you, I will keep that in mind! Even if you can't do EPROMs, just the output of some random commands I provide in MacsBug would be very informative.

Hey look, they fixed this problem in the IIvx/IIvi ROM. It has the exact same function (ROM offset $40800000 instead of $40A00000 though), but the jump table is much bigger now. So big, in fact, that I got lazy and stopped figuring out how many cases there were. All the rest of the added cases...

Even if you're not comfortable doing any ROM hacking, it's also possible to install MacsBug and run some commands inside it to gather some knowledge.

Hey everyone, I'm not sure exactly where to post this, so I'll put it in the Compact Mac forum. I've been talking with @Arbee about a weird issue I found in MAME when emulating the Classic II, and thought I should share it with the whole group. BTW, if you're not familiar with MAME, you really...

Last week I fixed an LC III that had this same symptom. Chimed and then nothing, no death chime and no video. The culprit ended up being one of the data lines on the onboard RAM. The ROM was fully connected to the CPU, but the RAM had one broken trace. I think it was somehow hanging up during...

My edit window expired, but I meant to say Atari Falcon here. Completely irrelevant to this thread, but had to correct myself!