On the topic of why you'd even want so much RAM: I think the biggest reasons would be to run A/UX, which is probably the one situation on an old Mac where just having more RAM will help, because UNIX operating system. The other situation would be if you were running 7.6.1 or 8.1 (with WishIWere or whatever) on such an '030 system.
The 900/950 can use 256 megs of RAM, and the main reason for that is almost certainly its purpose as a content creation and UNIX workstation. (The official was originally listed at 64, I wonder when that changed, it's likely just a result of bigger SIMMS becoming available.)
512MB in a 650/800 (same system, different case) would be neat, but I question what you'd really be doing with it that wouldn't be better done with something that has a beefier CPU and storage for the era. That won't stop people from doing it though, and it would be a sight to behold for sure.
Otherwise, In the actual '80s and early '90s if you needed 128 (or 256/512) megs of RAM for something you probably also needed a little bit more CPU horsepower than the 68030, and better software than Mac System 6 or 7.
In re ram temperatures: I would classify it as "abnormal" for memory in Macs to get really warm. Anybody else who has 64/128MB simms, do those get very warm? It may be worth finding cooler RAM for an LC series machine, ArmorAlley -- I personally believe that (especially if the RAM gets hot too) that hot-rodding LC-series machines with >100MB RAM and 10k SCSI disks will eventually cause problems, because those systems don't really have that much in the way of cooling.
The 900/950 can use 256 megs of RAM, and the main reason for that is almost certainly its purpose as a content creation and UNIX workstation. (The official was originally listed at 64, I wonder when that changed, it's likely just a result of bigger SIMMS becoming available.)
512MB in a 650/800 (same system, different case) would be neat, but I question what you'd really be doing with it that wouldn't be better done with something that has a beefier CPU and storage for the era. That won't stop people from doing it though, and it would be a sight to behold for sure.
Otherwise, In the actual '80s and early '90s if you needed 128 (or 256/512) megs of RAM for something you probably also needed a little bit more CPU horsepower than the 68030, and better software than Mac System 6 or 7.
In re ram temperatures: I would classify it as "abnormal" for memory in Macs to get really warm. Anybody else who has 64/128MB simms, do those get very warm? It may be worth finding cooler RAM for an LC series machine, ArmorAlley -- I personally believe that (especially if the RAM gets hot too) that hot-rodding LC-series machines with >100MB RAM and 10k SCSI disks will eventually cause problems, because those systems don't really have that much in the way of cooling.