Multipliers

[me]

Okay this has been bugging me for a little while now. Is it true that the Athlon 64 3800+ is physically identical to the 3000+ except it has its multiplier set higher ---- and does this justify it costing R2500 rather than R1000?

It's the physically identical bit I want clarity on, because if the multiplier really is just a simple software switch (which happens to be locked in the Athlon 64 like most modern CPUs), then we can be pissed off at AMD (Intel's no better) for charging 2.5x as much for.. nothing.

 

[werner]

most of the cpu's in any given family are all physically identical when you get inside (pls, of course cache etc matters amongst chips, but lets take the example given above)

but when cpu's are made from the silicon wafer, the purest silicon is in the centre of the wafer, and that is where the "best" chips come from...i.e. the chips that can run fastest at the lowest voltage. These chips are then used for mobile cpu's and for high end parts consumer cpu's.

Each chips is tested at a given speed (tested batches at a time) and the failures are noted, and put aside. So, if a chip fails at e.g. 3800+ speeds, but passes at 3000+ speeds, then that chip is set to 3000+ speeds and sold as such.

The cpu's are effectively "speed binned" depending on their individual characteristics. Sometimes supply and demand dictate that e.g. 3000+ cpus need to be made, but all pass at 3500+ speeds, so are sold as 3000+ and that is where the good overclockers come from (i.e. the chip had already passed at 3500+ speeds, but were sold as 3000+ so there is no harm putting them back to 3500+ speeds)

Hope that explains it.

P.S. the video card guys do the same.

 

[me]

Makes sense, thanks for the info.

I'd still be surprised if those extreme prices at the higher end can be justified by the better quality silicon, but I guess supply-demand and competition have a lot to do with those prices too.

I like to feel I'm getting what I'm paying for though so I always stick with mid-range stuff.

 

[werner]

it's not based purely on the better quality silicon, but more based on the actual production rate (supply and demand). All the silicon costs the same, but out of a wafer, you wont get a large amount of top end chips.

test 1000 cpu's...maybe 5 are good enough to be 4000+ chips...so, they are in short supply, difficult to produce and have quite a high failure rate (which then become slower model cpu's etc).

The nice thing is, as time moves on, production quality goes up, which brings prices down (maybe test 1000 cpu's, and 50% are good enough for 4000+ speeds) which means typically chips that run at lower voltages, with less heat, or good overclocking chips etc. Rule of thumb: when a new top end cpu comes out, dont buy it. Wait a few months (not only for the price to drop) but to get a later version of that cpu, more than likely it will overclock better due to the above reasons.
Doesnt hold true 100% of the time, but it is a good way to operate.

 

[LandyMan]

What kind of speeds will I get from using bath sealant silicon?

 

[me]

Well if you roll it flat and draw tracks on it with a pencil and put it in the microwave, you can get about 1.2 GHz.

 

[me]

Rule of thumb: when a new top end cpu comes out, dont buy it. Wait a few months (not only for the price to drop) but to get a later version of that cpu, more than likely it will overclock better due to the above reasons.
Doesnt hold true 100% of the time, but it is a good way to operate.

Yes I like that way of thinking!