Which is newer/better/more powerful?

Matt
Welcome to the Discussions.

Here are the specifications for the Performa and the PowerMac.

The Performa is the newer, and it has a faster and more recent processor and more slots for expansion, but only two of them are PCI slots.

If you're asking which of the two is faster the Mac Performa 6400/180 is faster. If you're asking which Mac you can put Mac OS X on with some upgrading that would be the Power Mac 7200/90; if you replace the PowerPC 601 CPU/processor with a G3 upgrade since OS X doesn't support the PowerPC 601 and wasn't designed to either. The Power Mac 7200/90 has three PCI slots while the Mac Performa 6400/180 has two PCI slots, a Communications II slot (you install either a network card or modem here), a TV slot for the optional TV tuner card Apple made or the rarer still TV tuner/FM radio card that goes with the card you install into the Video In slot (you can't just install one either; TV tuner card or TV tuner/FM radio card requires the card that goes in the Video In slot to work). Also the Mac Performa 6400/180 only supports up to Mac OS 8.0 (according to Apple anyways)because it supports less RAM and only has two RAM slots. The Power Mac 7200/90 has four RAM slots and unofficially supports up to 512 MB of RAM using 128 MB modules (Apple even notes this in its spec page but hasn't tested it themselves). It also supports Mac OS 9 while the other Mac doesn't and will support up to Mac OS 9.2.2 with the help of OS9 Helper (this is also why you're able to install Mac OS X on it with a G3 upgrade). So if given the choice between those two Macs I'd probably get the 7200/90. Here's a link to more compatibility info if you choose to get the 7200/90 and attempt to install Mac OS X on it using XPostFacto with a G3 upgrade: http://eshop.macsales.com/OSXCenter/XPostFacto/Framework.cfm?page=Compatibility. html. Also while OS9 Helper and XPostFacto are both freeware you have to pay a small fee to use the tech support forums for either (two separate fees).

Two corrections:
The 6400 will run up to 9.2.2, and max RAM is 136MB, including the 8MB soldered to the board.

It can also be upgraded to G3, but I'd not want to sink that much into a 6400. In either case, unless you're getting it free, I'd go looking for a Beige G3- they're really cheap now.

" If you're asking which Mac you can put Mac OS X on with some upgrading that would be the Power Mac 7200/90; if you replace the PowerPC 601 CPU/processor with a G3 upgrade since OS X doesn't support the PowerPC 601 and wasn't designed to either."

The 7200 (75, 90, and 120 MHz) series motherboards have a soldered 601 processor, which can't be physically removed/replaced. That's why the G3 upgrade path is more expensive or involved for them, compared to other Power Macs. Sonnet has a G3 processor card upgrade for the 7200's PCI slot, but the cost exceeds the price of used B&W G3s, so it's not a practical or recommended purchase. A less expensive way to upgrade a 7200 with a G3 processor, involves replacing the motherboard with one taken from a 7500, 7600, or 8500. These boards have plug-in processor cards, and compatible (used) G3 processor cards are relatively inexpensive at eBay. Having stated this, I wouldn't advise either upgrade path for a 7200 at this time. Beige G3s go for well under $50 at eBay now, so buying an older legacy Mac to upgrade to a G3 is a money poorly-spent, that you'll never recover (been there, done that). G3-upgraded Macs are still not the equivalent of native G3s, when all other hardware components are considered.