Two-Speed Processors

[Shrek]

With IBM's scaled down Power4 PowerPC processor reportedly coming out soon, I was wondering if it is possible to create a single two-speed processor that can run 32-bit applications at twice the speed that it can run 64-bit apps. What would be the limitations of such a technology? Would this even be an economically sound product to market in today's economy? Does anyone know?

 

[alex_ant]

I'm not a computer engineer, but I'd bet anything that it's not possible. If it were, I think AMD or Intel would have done it already.

 

[mnkeybsness]

i will be a computer engineer one day and i already know that it's not possible....yet....that's a very good concept that should be elaborated on and studied...hmmmmmm

 

[Mr. Anderson]

Re: Two-Speed Processors

Originally posted by Shrek
With IBM's scaled down Power4 PowerPC processor reportedly coming out soon, I was wondering if it is possible to create a single two-speed processor that can run 32-bit applications at twice the speed that it can run 64-bit apps. What would be the limitations of such a technology? Would this even be an economically sound product to market in today's economy? Does anyone know?

ok, just a thought, but if you had two speeds, why would you want one slower than the other? why not run the 64 bit apps at the same speed as the 32 bit apps and get better performance?

Am I missing something here?

 

[Shrek]

Dukestreet, it would be nice because currently 64-bit processors can only crunch data at up to 1GHz, while 32-bit processors can do it at up to 2.8GHz. So if 64-bit processors are generally slower than 32-bit processors, wouldn't it be nice to have a two-speed processor that is able to crunch 32-bit data at twice the speed? Am I making any sense? Did I "switch the light on?"

 

[Shrek]

I wonder if it'd be possible to do it by making a motherboard that can have two processors on it, but one would be 64-bit and the other a 32-bit processor.

Example: The first processor on the motherboard would be 64-bit only, but runs only at 2GHz. The second processor would be 32-bit only and runs at 4GHz!

Imagine that!

 

[nuckinfutz]

Depends on

If your goal is to crunch the most Data or attempt to clock the highest megahertz.


It's like saying is it best to go through a gallon of ice cream with a small spoon versus a large spoon. Well not many people will care if the end result is the same.

That's how I view 64bit vs 32bit. I don't care of a processor runs at 5mhz as long as my realworld speed is fast.

 

[bousozoku]

Originally posted by Shrek
I wonder if it'd be possible to do it by making a motherboard that can have two processors on it, but one would be 64-bit and the other a 32-bit processor.

Example: The first processor on the motherboard would be 64-bit only, but runs only at 2GHz. The second processor would be 32-bit only and runs at 4GHz!

Imagine that!

I've been thinking about your question since I saw it last night. There are so many reasons why it wouldn't work.

Now, this new question is equally interesting. It would be possible to put multiple processors into a computer. It's been done a few times with daughterboards plugged into the motherboard.

Research the Commodore SuperPET, a successful merging. It had a MOS Technologies 6502, Motorola 6809, and Zilog Z80. It was a most interesting computer. The 6502 was very efficient as well as crippled. It was a RISC processor in its own right with only 57 instructions. The 6809 was the closest thing to a 16-bit processor that an 8-bit processor could be. The Z80 was, to me, an exceptionally strong Intel 8080-compatible processor and the epitome of small computer strength.

The computer was a little expensive and a little awkward, but extremely capable.

Now, putting two incompatible word-size CPUs in the same machine...I don't think so.

 

[topicolo]

On a similar note, it would be interesting if IBM implemented something like Intel's hyperthreading system. Since a processor has both integer and floating point units, why not use them at the same time? In normal processors, either the integer units or the fp units are active, but only one at a time. If you were able to enable the processor to use both at the same time, wouldn't you get a significant speed increase in many applications? There would be a marginal increase in heat dissipation, but that can be offset by a better heatsink/fan. Overall, the manufacturing price of the chip shouldn't increase much at all

 

[alex_ant]

Originally posted by Shrek
Dukestreet, it would be nice because currently 64-bit processors can only crunch data at up to 1GHz, while 32-bit processors can do it at up to 2.8GHz. So if 64-bit processors are generally slower than 32-bit processors, wouldn't it be nice to have a two-speed processor that is able to crunch 32-bit data at twice the speed? Am I making any sense? Did I "switch the light on?"

Well, here is how I understand it. The difference between 64-bit and 32-bit in a CPU has nothing to do with performance or clock speed (GHz) - it has to do with the maximum word size the processor is able to handle. 64-bit processors are not generally slower (in terms of performance, not clock speed) than 32-bit processors - they are faster (in terms of performance, not clock). But not because they are 64-bit. They are generally faster because they are well-designed, have big caches, and are typically intended for high-end computers where no compromises are made for cost.

The reason 64-bit processors exist is because they are able to perform operations using twice the precision of 32-bit processors. What this means is that a 32-bit processor is limited to integers 32 or less digits long. Anything longer has to be truncated or rounded off. This sounds like plenty of digits for anybody, and it is for most people, but 64-bit precision is required for some specialized science, engineering, etc. tasks. This is why 64-bit computing hasn't caught on on the desktop yet, and why when it does, it won't be a big deal (hardly anybody will even notice). Personally I think it's kind of a laugh, like kids comparing the meaningless specs of their video game systems. "Mine has twice as much bits as yours, woooooooooooo."

64-bit CPUs are also able to address an order of magnitude more memory than 32-bit CPUs, but I think that can vary depending on the architecture.

Oops, I forgot about your question. A 64-bit CPU will never be able to run 32-bit code at 2x speed because... it just won't. That's not how CPUs work. So there you go.

(And now comes the part where I cross my fingers and hope I'm not wrong. )

Alex