FX-series processors in SMP

Good Afternoon, all:

Ok, correct me if I'm wrong with this: The FX series of processor cores and the Opteron 2xx cores are the same. The difference between the families is that the FX series does not have the multipliers locked but has the HT path cut, which disables the chip from doing SMP. The Opteron family does have locked multipliers, but does not have the HT path cut.

Assuming this to be true, the FX series of processor could be made SMP capable by re-enabiling the HT paths, much like the unlocking of the old Athlon series with the L1 jumper trick.

Assuming this to be true, AMD would have likely just cut bridges on the die in order to either enable or disable functionality on the chip. So, if certain bridges were reconnected, it would allow an FX-series chip to run in SMP.

Has anyone ever investigated this possibility? Is it possible to get to the die without destroying it?

I know the FX has less HT paths than the Opteron but more than an Athlon 64. I don't think the number of paths makes any difference in running them in SMP, at least with two cores. If you already have the board and the two chips I say plug it in and try it.

Back in the AMD day when they were making Athlon MP processors, someone figured out that the standard Athlons worked just fine in an MP board and had no issues with SMP, at the time I think this was at least a hundred dollar saving per chip. This was never documented in any way by AMD. I would assume the FX's being a premium priced chip I could see them looking the other way and not deliberately disabling SMP functionality.

What socket are your FX chips? My 2xx Opterons are socket 940. I'm kind of assuming your looking to run a pr. of FX chips together? (SMP as multi-proc.)

Zerix01 said:

I know the FX has less HT paths than the Opteron but more than an Athlon 64. I don't think the number of paths makes any difference in running them in SMP, at least with two cores. If you already have the board and the two chips I say plug it in and try it.

Back in the AMD day when they were making Athlon MP processors, someone figured out that the standard Athlons worked just fine in an MP board and had no issues with SMP, at the time I think this was at least a hundred dollar saving per chip. This was never documented in any way by AMD. I would assume the FX's being a premium priced chip I could see them looking the other way and not deliberately disabling SMP functionality.

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I've heard something similar. Supposedly, the FX series has two HT paths, but it needs three to do SMP (the last HT path for processor to processor communications). I remember that whole Athlon XP/MP affair....I was one of those people running a pair of Athlon XP 2400's in SMP, and it worked just fine. Though, I did have one MP and one XP, even though that *really* shouldn't have worked well (completely different stepping on them), that thing was so utterly stable, even with a gentle OC, I ended up using it for my media server.

I also post at 2cpu.com, and according to popular consensus over there, 2 FX series processors really won't work in SMP. I'm going to give it a try anyway once my new board shows up (I blew up my MSI board the other week....let out the magic smoke from a few caps. Oops). It seems as if AMD may have pulled a modern-day version of the laser-cut L1 jumpers, only they were smart enough to hide the cuts somehow. Thus far in my researching it, no one seems to have a really solid idea as to exactly what they changed between the FX cores and the Opterion cores, if anything. I sorta suspect that what you think is true: it'll work, but AMD just never said it was possible.

Donuts: Yup, I have a pair of FX-53's, socket 940. I have a SuperMicro H8DCi that I want to run the pair of them on, and it seems as if AMD has some other plans for me. So, naturally, I'd rather one-up AMD and get them to work anyway!

Cool,
I thought that i had read somewhere they wouldn't work, but I don't know anybody who has actually tried it. Keep us posted.

RedShoeRider said:

I've heard something similar. Supposedly, the FX series has two HT paths, but it needs three to do SMP (the last HT path for processor to processor communications).

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I have never heard of any HT paths having specific uses. What I had made of it was they all can be used for the same thing, just more paths equal more bandwidth. But I'm just basing this off of assumptions, maybe someone can dig up a white paper that says if you need X amount of HT paths for SMP.

But really what good would adding the extra HT path to the FX's vs the one the Athlons have? The only reason I can come up with is more bandwidth to various peripherals, like a large (6+ drive) RAID array. Really unless you are overloading the bus I don't see SMP having an issue with only two paths.

From what I understood, the extra paths were basically CPU links. (I was far from an expert, but I did stay at a Holiday Inn Express once )

Supposidly, the 1xx optys (including FX) could do 1 way. The 2xx optys up to 2 way. (single or dual proc.) The 8xx series, up to 8 way.