The 64-Bit Question

Continued from page 4

By Simson Garfinkel

June 2, 2004

128-bit Bound?

Having lived through the jump from 8 to 16 bits, then 16 to 32, and now 32 to 64, it's only natural to think that sometime in the distant future we'll be making the transition from 64-bit to 128-bit systems. Don't hold your breath. 

The important thing to remember here is that bits are exponential. A 32-bit system can address 65 thousand times as much memory as a 16-bit system, while a 64-bit system has a theoretical memory address space 4 billion times larger than that of a 32-bit system. You could actually build a single memory system that would hold 2⁶⁴ bytes of storage with today's hardware-but you would need to use more than 200 million hard drives, each one holding 256 gigabytes of information. That's more storage than was delivered by the entire world's hard drive industry in 2003. So while it's conceivable that you could build a memory system holding 2⁶⁴ bytes of storage today, you would probably have to use every computer in the world that's connected to the Internet.

Although it's possible to envision a future where computers will access 2⁶⁴ -byte databases, it's hard to conceive of a single problem that would require a program to have that much  memory accessible in a single address space. One reason why such an incredibly big system doesn't make sense is that you wouldn't build such a system with a single processor and a single unified address space: you would instead use millions or billions of processing elements, all with overlapping memory and responsibility. That way, if one processor or block of memory failed, the other systems would take over seamlessly.

Given such arguments, it's pretty unreasonable to imagine that you would need 2¹²⁸ bits of storage-not in our lifetime, not in anybody's lifetime.

On the other hand, I could be completely wrong about all this: 64 bits could be just the thing for doing full-body virtual reality with mind-meets-mind-morphing capabilities. Or more likely, companies like Dell might choose to follow Apple's lead and stop selling low-end machines with 32-bit processors, instead relying on the marketing hype of 64-bit machines to justify the higher profit margins.

But remember, there's always room at the bottom. And since 32-bit machines are likely to be useful for at least a decade to come, if not longer, I would be surprised to see Dell cede this market to another company. Just look at Apple: while all of the PowerMac desktop machines that Apples sells come with  G5 processors, the company is still using G4s in its iMac, eMac, and PowerBook computers.

Personally, I think that 32-bit systems will be with us for a long time to come.