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RE[3]: my dream
by Morin on Tue 23rd Oct 2007 02:29 UTC in reply to "RE[2]: my dream"
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> Creating a 128-bit or larger processor is a piece of cake anyways. All
> you have to do is enlargen the instruction size and mingle with the
> microcode. If I'm not mistaken...

The details are a bit more complex, but yes, it would be piece of cake if there was any market for a 128-bit CPU.

> But if you are starting a new and using a larger address space doesn't
> seriously hurt performance, then why settle for less? Why not embrace
> the future right now?

Increasing address space size *does* hurt performance. Modern programming sees a lot of "passing pointers around", and even more so in reference-eager programming languages such as Java or C#. All those pointers would now be twice the size, meaning the size of the CPU cache measured in number of pointers halves and resulting in more actual memory accesses. And those are *really* bad for performance. Similar arguments apply to instruction size.

Unless you are changing to an entirely different memory model (e.g. non-uniform pointer size), 128-bit addressing would kill performance.

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