CGs: How To Find Them

There’s two pictures of CG revision Athlon 64s here

The top picture shows is a Newcastle (that means 512K rather than 1M cache), stepping revision CG, default speed at 2200MHz.

The bottom picture shows a “regular” Athlon 64 with 1M cache, stepping revision CG, running at 2000MHz.

How can I tell that? I can tell that from the codes.

How To Tell A Newcastle from a Regular Athlon 64

Newcastles have a “4” in the third-to-last character in its OPN. So, in the case of the top processor in the picture: ADA3200AEP4AX

“Regular” Athlon 64s have a “5” in that same position. So, in the case of the bottom processor in the picture: ADA3200AEP5AW.

Where does it say that? It says that in this AMD datasheet (page 6).

That same page says a few other things, too.

How To Tell A CG Stepping Chip From Earlier Steppings

Up to now, the current stepping for Hammers has been the C0 stepping. The stepping of a Hammer is indicated in the last two characters of the OPN. In the case of an Athlon 64, a C0 stepping chip uses the code “AP.”

No matter what type of Hammer it is, the last character in the OPN of a CG-stepping processor will come after the letter “P.” For Athlon 64s, it will initially be “AR” and “AX.” For Athlon FXs, it will initially be “AT.” For mobiles, it will be initially “AR.” For Opterons, it will initially be “AT,” “AU” and “AV.”

This information for 64s, FXs, and mobiles can be found on pages 6, 11 and 14 of the abovementioned datasheet The information on Opterons can be in this Opteron datasheet (page 6).

There’s More To The Story

That seems simple enough, doesn’t it?

If you order online, Newegg does provide a picture which usually indicates what they’re shipping. As of now, the pictures show “old” processors, and while somebody who just bought a 3400+ said he got one, don’t count on getting a CG 2800+ quite yet.)

However, if you look at some other recently revised AMD datasheet, you run into a big surprise.

A Big Surprise…

the revision guide for Hammer processors, you’ll find that there is not one CG stepping, not two, but three different CG stepping for Athlon 64s (and mobiles), all with different stepping codes for CPUID.

There is the SH7-CG stepping. For A64s, this will have a model number 4 and a stepping number of 10 (or A; A means 10 in hexadecimal). This particular stepping will also be used for Opterons, FXs and mobiles.

There is the DH7-CG stepping. For A64s, this will have a model number 12 (or C), and a stepping number of 0. Only Athlon 64s and mobiles will be made with this stepping.

Finally, there is the CH7-CG stepping. For A64s, this will have a model number 8, stepping 2. Again, only A64s and mobiles will use this stepping.

Which is which?

Given that processors like the Opteron and FX, which will definitely continue to have 1Mb cache, will use only the SH7 revision, one might suspect that the SH7 is the CG version for 1Mb cache chips, and the others are for Newcastles.

This gets confirmed in the later parts of the revision guide. Look at the fine print on pages 9 and 10, and you’ll find out that the ARs are 1Mb cache chips which use the SH7 revision, and AXs are the 512Kb chips which use the DH7 revision.

The Case of the Missing Stepping

That accounts for two out of the three steppings. But what about the CH7 revision?

We don’t know. We know it exists, but outside of CPUID, there’s no indicator to distinguish it from the others.

The only hint we have about the nature of the beast is that from its designation, the CH7 stepping was likely made before the DH7 stepping, which implies that the DH has some improvements over the CH.

This may merely mean that they made a few of them, then went on to something better. It might mean that we may see some Athlon 64s with the last two letters somewhere between “AR” and “AX” showing up eventually, perhaps for the lower end A64s. (It’s far too premature to think these are Parises, AMD releases this kind of technical data to the public only when they’re ready to release the products.)

We just don’t know at this point.

There’s a few more tidbits from these datasheets.

An Appearing and Disappearing Act

Something else also shows up in the revision guides: CPUIDs for the socket 939 versions of Athlon 64s. It is safe to say that all socket 939 chips will be CG revisions. Socket 939 will come in both 1Mb and 512Kb versions, but we already knew that.

What is curious is what does not get listed. There is an FX revision listed, but no socket 939 version of the FX listed in the revision. AMD was careful to give different CPUIDs to the socket 754/939 versions of the chip; why wouldn’t they do that for the FX, too?

Yes, this is a distinction without any real difference, since there will be an socket 939 Athlon 64 with 1Mb cache, or simply an oversight, but it looks odd.

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