Well, I added an OrangeLink FireWire/USB2 combo card to my G3/300 (beige). I've hooked up a FireWire 400, 120GB disk, and I can't copy from the G3 to the drive. Anything larger than 15MB will hang up around halfway. It's very frustrating - it didn't hang up once, it's a recurring problem. So what can I do...replace the card? 
Second, I'd like to know what causes MDS (motherboard death syndrome). It happened on 3 of my Macs. The Mac refuses to do anythign when any of the power buttons are pressed. These things are certain:
- It's not the power supply. Motherboard gets damaged.
- It's not a power surge causing it
- Replacing the battery doesn't help
- Ditto for disconnecting everything, 3rd party devices and PCI cards
- It's not because I installed something and shocked a component or anything like that...it just does it all of a sudden won't boot
Nothing is to be done but replace the mobo. Scary.
Third, one of my friends still has a 7500/100. I want to help him out a bit (since he can't get a newer one). There is a dead 8600 in my office. Will the CPU and RAM from this machine work in the 7500?
I called Apple on this, and they said go for it (reminding me that it's not covered by the warranty. Why thank you! Would a 7500/8600 have a warranty by now???)
Then I talked to one of my Apple friends, and he said that the 8600 card won't work in the 7500 because it's Mach 5 (5V) whereas the 7500 is 3.3V. I'm afraid he's right 
Thanks for the awnsers every1...
Did you try pressing the CUDA button?
If it's the 8600s power supply that's dead then transplant the whole motherboard into the 7500s case,
If not then the RAM and VRAM will work in the 7500. Also the 8600 will have a much faster CD drive and maybe a faster hard drive. If the power supply is good he may be interested in moving his motherboard over to the 8600 case.
Wayne
Hey genius! 68K Macs don't HAVE cuda buttons.
Wayne: no, I think it's the motherboard that's having issues. I've already found a home for the CD/HD...hmm...there is a lot of difference between the 8600-7500 mobo (even though it ain't physical).
Thanks for the reply.
~Mackie
Depending on the speed of the 8600, the CPU daughtercard will work in a 7500. The 200mhz card will work since it's not Mach 5, but I think the 250 and faster cards will not work.
If the 8600 has a cache slot on the logic board, that should indicate that the CPU card is 3.3v.
Hey Mackie -- ease up, there. No need to be rude, especially if you're wrong. It's true that 68k machines don't have CUDA buttons. But the 7500 and 8600 are not 68k machines. They're PPC machines, and they certainly do have CUDA buttons, right behind the CPU slot (the button is just about directly beneath the part of the CPU card that overhands the CPU slot to the rear).
As for 8600 and 7500 transplants, an 8600 mobo will go right into a 7500 case and interface just fine with all its connections. This is true regardless of whether the 8600 mobo is a standard model (shipped with standard 200MHz 604e CPU) or Kansas mobo (shipped with Mach V 250MHz or 300MHz 604e). The 8600 mobo's edge connectors for SCSI, power, etc. are tilted 90 degrees compared to the 7500, so they face outwards on the edge of the mobo instead of up; but the connectors are sufficiently low-profile that this makes no difference.
As for RAM and such, everything from the 8600 will work with the 7500. The only exception is that if the 8600's CPU is 250MHz or 300MHz, then the CPU won't transfer over to the 7500. As for RAM, all varieties of the 8600 take the same RAM as the 7500. The 3.3V issue is for the CPU slot on Kansas/Mach V setups. Otherwise the voltages are all the same for the 7500 and 8600.
Finally, as for cache slots, the 8600/250 and 8600/300 should have no cache slots, because their CPUs have 100MHz "inline" caches soldered onto the CPU card. Only the 8600/200 will have a separate L2 cache slot (though I'm willing to wager that 8600/250 and 8600/300 mobos still have the solder pads for the cache slot connector).
(As a side note, a 9600 won't have a cache slot regardless of which variation it is: the Kansas/Mach V units have the inline cache on the CPU card, and the older versions have the cache chip soldered directly to the mobo.)
Matt
The 5V-CPU 8600/200 will have a cache slot. An 8600 with a 3.3V CPU will have the cache RAM soldered directly onto the CPU card.
Matt
my bad.... Got the numbers switched around!
You're the genius. I see no mention of 68k Macs in your original post...you only talk about 7500s and 8600s, which DO have them.
If I have a 9500 board and an 8600/200, I can take the 8600 logic board out and place the 9500's board in its place?
Well a 9500 (and 9600) board will have 6 PCI slots. So I'm not sure if it will fit. Also, Apple made some changes between the 8500-9500 series and the 8600-9600 series, so I'm not sure if all the connectors are the same.
I think someone more experienced with 9500s will have to weigh in here. Sorry!
Best,
Matt
-- I can barely remember my own phone number these days!
Matt
I have an 8600/200 and a 9600/300, and parts of a 9500/132. The 8600 case is the same size, but the lower 3 slots on the case are not used. There's a plastic spacer if memory serves me correctly.
I'm not too sure about the connectors. When comparing the 8500 logic board against the 8600, the connectors on the 8600 logic board are at a 90 degree angle in relation to the board.
8600 MLB can use a 7300 PS, but the 7500's PS won't plug - n - play. Might be able to mod it, but I haven't done that so can't comment. Hmm, doesn't the 7300/8600/9600 have a 3v line lacking in the 7500/8500/9500 PS . . . or something? Too lazy to go look it up.
Otherwise an 8600 MLB will fit and work fine in any 7500 form-factor box.
Any processor card slower than 250 ought to be pre-Kansas and should work in the 7500. Mackie doesn't mention the dead 8600's speed . . .
dan k
No. The 8500/9500 and 8600/9600 cases are different sizes...the 9x00s are taller to accomodate the 6 PCI slots.
Oh, thanks for the replies. The dead 8600 is a 300MHz model, but I'm quite sure it has a cache slot. I'll go check now...
I have both 8600 and 9600 Macs. Unless you look inside an 8600's case, you can't tell it's a 3-slot logic board. The back of the 8600 still has slot covers for 6 slots, even though the bottom 3 are not used.
I'll 2nd that