Ok, poking around my computer with the resource monitor today, I noticed that my AMD Phenom II N870 Triple-Core Processor powered machine is showing 4 cpu’s, the expected 3 labeled cpu0-cpu2 and a mystery (to me) cpu labeled “service cpu”. Mostly the service cpu was inactive until I opened my browser while running distributed computing software (currently running between 60% and 70% on service cpu). Research has not yeilded any insights to me beyond the fact that my processor does have 4 physical cores with one factory-disabled. So I need a computer hardware savvy person to tell me whats possibly going on. Did AMD goof and forget to disable a batch? Is Dell somehow turning this cpu back on? Did the Geek Squad guy at Best Buy do something to it before I bought the machine? Is this cpu a virtual cpu and not physically present at all?
That’s the CPU usage by system services, not a physical CPU.
As you noted, though, the AMD triple core processors are quad cores with one core disabled.
Out of curiosity, why do they do that?
I don’t know for sure but I would say that they do it to improve yield. When you build chips a large percentage of the chips don’t work because of manufacturing defects around 50 to 75 percent don’t work. If you find that a lot of chips work except for one core you could still sell those chips as 3 core processors.
Oh, ok, never would have thought of that, thanks yabob
the rumors I found posted around the internet Fubaya are that a certain unstated percentage of them have a faulty core so AMD disables it and sells them as 3x to save having to eat the whole thing and just refined or replaced/repaired the manufacturing process to reliably churn out working 4x processors
aaaaand beaten to the punch on the disabled core
I always thought it was to provide a range of price options. They have a single assembly line creating quad core processors and disable some of those processors to let them sell an economy line. It is much more expensive for them to create another chip that only has two or three cores.
If I am not mistaken, some motherboards have the ability to “unlock” some of those disabled cores.
And the practice is far from new.
Intel did the same thing with the 486 SX/DX lines. Math coproccessor worked, DX, math coprocessor not working, SX.
You are both right.
The processors are designed so that individual cores can be enabled and disabled, with the intent that if a core was defective they could just disable it and sell it as a 3 core processor. So they designed it from day one that the 3 core would be a cheaper processor that would not only fulfill their desire for a less expensive processor but would also allow them to sell many of their defective 4 core processors, increasing their effective yield.
However, they have on occasion had to disable one core of perfectly good 4 core processors just to meet the customer demand for less expensive 3 core processors. So once in a while, you can re-enable the 4th core and actually have it work. Usually though, re-enabling the 4th core will cause the computer to crash because more often than not, the 4th core really is defective.
But hey, if you already paid for the processor, you might as well give it a shot. You could get a 4th core for free if it works, and if it doesn’t work, you just disable it again and you haven’t lost anything.
But I still don’t get how the 4th processor in the OP is labeled “Service CPU”. Aren’t multiple cores supposed to be perfectly symmetrical / interchangeable on a Wintel PC?
I don’t think the 4th one is labeled service CPU. I have a two core intel chip in my laptop. In Resource monitor see Service CPPU usage, cpu0 usage, cpu1 usage and cpu total usage.
It is certainly for yield - today it is all about yield. Caches come with extra rows and/or columns which allow bad bits to be repaired during manufacture. Some 8 cores systems come in 6 core varieties also. You want to limit the number of configurations to not confuse the operating system and to make a reasonable number of part numbers.
I don’t know about AMD processors, but the multicore ones I’m familiar with have the core configuration blown into their efuse array, which cannot be changed by the OS.
BTW, I have no idea of what AMD yields are, since that is a closely guarded secret, but I’d suspect they are considerably above 50% after memory repair for an X86 processor - at least in volume manufacturing.
Not new at all. And a lot older than that.
IBM began offering ‘field upgrades’ on some versions of its 370 Mainframe computers early in 1977.