Difference between CPU "Stepping" & "Revision?"

[thetxstang]

I'm fairly new to the exciting new world of BYO PCs and overclocking. I've come a long way and have built a few systems now, all overclocked to one degree or another. However, I'm still unable to get decisive info on what the difference is between processor "stepping" and "revision."

Do the two terms mean the exact same thing, or is one a subset of the other? Thanks in advance to anyone that can help me understand this.

 

[3chordcharlie]

I think a revision would coincide with a core change (like a die-shrink, or added features, etc) while a stepping is more basic, with maybe some bug fixes.

 

[jiffylube1024]

Often they're used interchangeably, but not always and they're actually defined differently.

stepping refers to chips of a specific manufacturing process (like "Northwood" for .13um Pentium 4's) whereas in a P4 Northwood M0, M0 is considered the revision of the CPU.

If you use the program CPU-z, it will tell you the stepping and the revision.

 

[thetxstang]

3chordcharlie and jiffylube1024, thank you both for your responses. However, it appears that your answers contradict one another, if I'm not mistaken. At any rate, it does seem that one indicates a major CPU change while the other represents a minor change. Can anyone else provide some additional insights?

Originally posted by: jiffylube1024
If you use the program CPU-z, it will tell you the stepping and the revision.

Funny, it was CPU-Z that actually prompted my question in the first place. I had always thought "stepping" and "revision" were the same thing until I noticed CPU-Z differentiates between the two.

 

[3chordcharlie]

Well I posted what I've always thought the difference was, but now I'm interested enough to probably check back and see 'the answer'.

 

[thetxstang]

Originally posted by: 3chordcharlie
Well I posted what I've always thought the difference was, but now I'm interested enough to probably check back and see 'the answer'.

I tend to think your answer was the proper one, based on some of my research. That said, Google has NOT been my friend in my endeavor to ascertain the difference, once and for all.

 

[pm]

I'm not sure what people mean by revision. I would guess it's interchangeable with stepping.


For the definition of stepping, http://www.anandtech.com/guides/viewfaq.aspx?i=6

A stepping is a revision of silicon - to be more precise it refers to a change to the mask used to manufacture the chip. This change can for any number of different reasons: to improve bin split (frequency), to fix errata (ie. bugs), to improve yield, to solve an electrical issue and other misc. reasons.

Intel defines steppings in two forms. A letter change is a change to the complete set of masks. A number change only refers to a subset of the masks. So, A1 -> A2 is a change to just a few layers (usually metal), while B0 -> C0 is a change to all layers.

The most important point to remember about steppings is that you shouldn't mix them in a SMP (multi-processor) system. If you have one 733MHz Pentium III cB0 CPU, and you want to add in another to make a dual-processor setup, then I strongly recommend getting another 733MHz Pentium III cB0, and not putting in a 733MHz Pentium III cA2 or a cC0 instead.

Intel does, however, support mixed steppings for Dual Processing operation for certain Pentium IIIs. Full details, along with the Mixed Stepping Matrix, are contained in the Intel Pentium III Specification Update.

You could think of it as a software release. But it's worth mentioning that rarely steppings are released that may have no notable diffence to the prior stepping as far as the end-user is concerned. A stepping for a yield improvement would not be noticeable at all to the home user. Software releases are almost always released for a reason that would be noticeable to the end-user.

And yes, later should always be better.

 

[Effect]

I may not be the best one to describe it, they do seem a little 'grey', i think 3chordcharlie put it well. The revision is a fairly noticeable change in the processor (by noticable, i mean the specs of the chip are different, like 3chordcharlie said, perhaps a die-shrink), whereas a stepping is pretty much a minor change or alteration done to the cpu, which may affect things such as o/cing (tho the rev may impact this as well). Newer rev's are almost always better, but newer steppings may not be.

 

[PentiumIV]

Depends on whom are you asking.
Intel only speaks in terms of "steppings", as Patrick described.
Apparently, AMD revisions = Intel "full steppings"

 

[hans007]

intel has both steppnigs and revisions.

i.e. some of the more beta versions of say ES cpus that are shipped out are a0 revision but what publicly gets shipped is say a1. maybe they will make the release version a1, but it is basically the same design with maybe some fixes.

generally the changing of stepping is like, a drastic feature change. like say for intel presler cpus the stepping changed when they fixed eist, and enhanced halt state in the intel 965 cpu.

it seems though that generally, they only publicly release one revision, but eventually change steppings. i think prescott 478 cores were either c or d step for example. and the 775 ones were d or e step. etc.