Until now we have seen x86 chromium netbooks and ARM powered chromebook laptops. But soon we will see chrome OS-powered MIPS chromebook laptops. MIPS is currently owned by Imagination Technologies. Lately Coreboot which is open source BIOS has been updated to support MIPS laptops.
One of the primary benefits of a diverse CPU landscape is that viruses would be harder to write, since the virus writer would either have to target many architectures or target only one and accept that their field of potential victims is much smaller.
Another advantage is that Intel would not hold an effective monopoly on CPUs. Manufacturers would have to compete against each other for market share. Or, manufacturers could specialize and target different niches. That actually has happened in a small way already. ARM is the CPU of choice for almost all smart phones. MIPS is often used in routers and other low-power consumer devices. But neither use stretches the capabilities of the CPU architecture like x86 has been stretched by the diversity of roles for which it has been used. So it will be great to see some MIPS chromebooks around. MIPS placed hardware simplicity over all else. I wouldn’t doubt what the article said about performance per die area.
MIPS cores are very simple. One of the most obvious examples is how it does virtual memory. (I’m not up on the latest, but I don’t think they would have changed it.) When an x86 or ARM processor needs to translate a virtual page address into a physical page address, hardware walks an in memory tree to translate the virtual address into a physical one. In MIPS, it traps to the kernel (that runs in physical address land) and lets the OS sort it out.
In both cases the translation of virtual to physical addresses happens in chunks of page size, and there is a cache of the most recently used translations. Letting the OS sort it out is neat, flexible, and saves tons of transistors, but costs time for translations.