[Rainy Day]

It looks like one can upgrade an early 2006 17-inch iMac (MA199LL, aka iMac4,1) with a 64-bit Core 2 Duo CPU, effectively turning it into a late 2006 17-inch iMac (MA590LL). Question is, will this allow it to address more RAM (i.e. up to 3GB), like the MA590LL? Was the 32-bit CPU the reason for the 2GB RAM limit?

Trying to decide if it makes sense to upgrade an old iMac running Mac OS X Leopard Server to Lion. The machine has adequate performance, but it would be nice to have more RAM. With compatible Core 2 Duo's running about $80, this may be a decent way to go.

[Waragainstsleep]

Very good question. I suspect you'd have to try it to answer it.

[Rainy Day]

I suppose there's also the question of whether the firmware would need to be flashed to even get 64-bit capabilities from the CPU? So it's conceivable that upgrading the CPU won't achieve much of anything (if it can't run in 64-bit mode)… except maybe a faster rate on the new CPU.

At any rate, it's beginning to look like Lion works on 32-bit CPUs, even if it won't be officially supported (which remains an open question until Apple publishes its minimal hardware requirements list for Lion). For more info, see: Mac OS X Lion *does* run on Core Duos/Core Solos

Apple seems to have an arbitrary cutoff of the systems it supports with each OS refresh, maybe around 4 years? It's hard to say whether this cutoff is to drive sales of new Macs, or for other reasons, like performance concerns, to reduce their compatibility testing or other support costs… or some combination thereof. I suppose it's hard for Apple to justify the cost of officially supporting older Macs while the number of users upgrading to Lion on those old machines rapidly declines. While original owners will most likely want to upgrade, a lot of older machines get sold to people less concerned about having the latest and greatest. I doubt Apple cares if users jury-rig Lion to run on unsupported systems, so long as it doesn't increase their support costs.

I've seen this before. Thanks to XpostFacto, i was able to install and run Panther on a Wallstreet PowerBook, even though Apple dropped support for it when Tiger came out, IIRC. But each generation of Mac OS X that i installed on that old Wallstreet performed better than the previous, XpostFacto notwithstanding.