Well, back in the classic Amiga days, games (and software) didn't need much memory and the Amiga's OS was on a 512K rom chip (or two 256k chips). This means that very little RAM memory was required for the Operating system, Thus Games (and apps) had nearly the full 1meg to themselves.
Going back to games, the graphics were all 2D, low res and only 5bit planes deep, not much memory required for that!! Sound samples were 8bit and usually at about 8Khz, again not much memory needed for that...
Modern games are 3D, generally run at 1026*768 and 32bits deep, this requres a huge amount of memory (Mipmaps, bumpmaps, textures, the list is endless). Sound is at least Stereo, 16bit at 44.1KHz, which requres about 10meg for 1 minute!!! Some games have surround sound, at 24bit and 96Khz!!!!!
If you run AROS on a normal x86 PC, aside from the Memory required for the Kernel (AROS has to use RAM as the PC has no Kickstart ROM chip), it doesn't need any more memory than AmigaOS. The Whole AROS OS fits on a single floppy disk with room for some software too!!!!
Which shows that most of the inefficency with the Modern PC is due almost completely to Micro$oft, and their bloated OS (Linux is no dream either).
Also IA64, has nothing to do with x86. It is an EPIC (VLWI to normal people) CPU, it was designed when chip desigeners thought the CPU couldn't perform optimisation in hardware, and so it has to be done in software increasing code bloat. The P4 and Athlon have proven that Hardware is much more efficent than software at producing small and fast code.
The Athlon64 is a much more modern design than the IA64, and basicly gives the x86 an optimised 64 bit mode. The Long Mode (64bit) on the Athlon is like a new CPU, but keeps all the good points of the x86 (as Linus put it), best of all it can still run legacy code which makes it far more economically viable (thus cheaper CPU, with more proccessing power).
I hope that helps
