[OuTpaTienT]

The main difference is one can run faster than the other.

When cpu's are made they are then tested and given a speed rating based on how fast they test. And as the manufacturer continues to fabricate the same family of chips they get better at the process as they go along, thus they start producing more high quality chips which means faster chips.

Also, from the beginning of the fabrication process they might be getting mostly slower chips (1500, 1600, etc) but they also will get a number of really good faster chips. And what they do is stockpile the faster ones until they are ready to release that speed of cpu.

At least that's my understanding of it. I'm sure you can get much more technical about what goes on, but in a simplistic nutshell that's it.

They release the chips that the market is calling for. For example, many, if not most, of the old Slot-A Athlon cpus were actually much faster chips than they were sold as. This was because AMD got such a high quality chip from their process they actually didn't have enough slower chips to fill the market demand. So they took their chips and marked them down a few speed ratings and sold them. I bought a 500Mhz Athlon and upon opening up it's case I discovered it was actually a 600Mhz chip. Then not too long after that I got a 700Mhz Athlon that turned out to be a 900Mhz chip. Ahhhh, the good old days.