: The game's map files are baked to be memory mapped to a fixed address, which
: is part of how they achieve such fast load times (the most time consuming
: part is loading assets like textures, etc, which aren't fixed to a
: specific address and may not be sequentially laid out on disc). So a
: weapon definition in a map file is laid out exactly how it will appear
: once loaded into memory. So there are pointer-sized fields within the map
: files. Some of the data structures might have required a different (ie,
: greater) alignment for a 64-bit platform. This would also be reflected in
: the map file too.

: So everything on disc that is directly memory bound will have to be 64-bit.
: For Halo, this is a lot of data, but I doubt it would result in anything
: more than each map file growing by a MB or two in size.

Even if it's a memory image of sorts, if the data only requires 32-bit precision, wouldn't it be feasible to store it in a compact 32+32 format on the disc, and have the CPU (or perhaps GPU, really) unpack the data as it comes in? In addition to potentially saving disc space, I wouldn't be shocked if it reduced load times when there are large contiguous areas of data.

Between the parallel processing capabilities of this hardware and the fact that these memory accesses would be highly patterned on a 68GB/s, I'd expect the HDD to be the bottleneck.