The Definitive Guide to Installing ESXi using iPXE...

[robinsmidsrod]

Actually, the sanboot http iso support in iPXE is very similar to how memdisk does things, it only uses much less memory, as it uses ranged HTTP requests instead of downloading everything before starting. But as long as the ISO in question supports running purely from ramdisk things just work (and ESXi 5.0 seems to do that).