AM2+ versus AM3 Motherboards and CPUs, clarification needed

[superj]

Currently I have an Intel system, but have watched with curiosity the Phenom II launch. I've been thinking of getting a Intel Quad, but would love to mess around with an AMD system.

I'm a bit confused about AM2+/3 sockets though. It seems like they are more forward and backward compatible than I thought.

From my reading this is what I've come up with, correct me if I'm wrong:

1. AM3 boards are all DDR3 only
2. AM2+ boards are all DDR2 only
3. AM3 CPU's work in AM2+ boards
4. AM2+ CPU's don't work in AM3 boards
5. Chipsets are the same for AM2+ and 3 boards (AMD hasn't released a new one yet)
6. AM2+ boards may be more cost effective for now because of DDR2 relatively cheap cost
7. DDR3 doesn't give you much on it's own, unless you start adding more memory channels ( like Intel's i7 triple channel memory controller)

Seems like the best purchase for now would be an AM2+ board with an AM3 CPU for future upgrades. Do the AM3 CPU's do anything extra other than DDR3?

[kirk_d]

Everything is bang on, until #7
I don't think anybody knows for sure!
Only time will tell; They could change their minds again!

[kirk_d]

I'm intrigued by the AMD 720 BE.
3 cores! Who would have thought?

[CMetaphor]

1. AM3 boards are all DDR3 only. Wrong actually, AM3 supports DDR3 and DDR2 RAM.
2. AM2+ boards are all DDR2 only. Correct.
3. AM3 CPU's work in AM2+ boards. Correct.
4. AM2+ CPU's don't work in AM3 boards. Correct, AM3 actually has 938 pins, rather than AM2+ with 940 pins. Therefore, my direct pin incompatibility, an AM2+ will physically Not Fit in an AM3 motherboard. And no, you can't just snap off the two extra pins I recall a website tried, although I can't remember which at the moment.
5. Chipsets are the same for AM2+ and 3 boards (AMD hasn't released a new one yet) Not as yet, but there has been mention of the 800-series of chipsets, epecially the 880G (which will replease the 780G as an HTPC-type motherboard chipset). Check out the threads started by myself and SKYMTL for some more info on it.
6. AM2+ boards may be more cost effective for now because of DDR2 relatively cheap cost. Again correct, DDR3 still costs about 2-3 times as much... and the benefits of using DDR3 in dual-channel on the current platform (I.E. 790FX/GX) is only around a 10% gain. However, in the future, hopefully with the 800-series chipsets, AMD may introduce tri- or quad-channel setups to further increase that benefit and compete more with i7.
7. DDR3 doesn't give you much on it's own, unless you start adding more memory channels ( like Intel's i7 triple channel memory controller) See my previous answer, hehe.

Any other questions?

[Exmortis]

You are correct, but again #7 is more intel marketing then truth, all benches I have seen with triple vs double channel i7 show no real tangible benefit. Same with DDR3 on PII, the difference isnt much, especially since AMDs memory controller is more timing sensitive then speeds. I think right now the AM2+ CPU will do you fine, again budget suggests its a better deal, my bet is you will upgrade again before moving off the DDR2, so you can always get a AM3 cpu then.

DDR3 like DDR2 when it came out has a long way to go, it timings are so loose you can drive tanks between them. Eventually as DDR2 did, it will get better and show the benefit, but I am not worried. You can buy 8GB of decent timed DDR2, which will be better then less DDR3 for more. Same issue way back with DDR vs DDR2. Early tests show the DDR3 on AM3+ isnt a big deal, I also think with the economy the way it is around the world, R&D will take a nose dive so do not expect any real world break throughs for many years to come. 2012 is what TMSC is predeicting before the chip market recovers. Thats an aweful long time, I think we will have to live with current tech for a little longer then usual.

The US economy isn't showing much signs of recovery, and although they ar epouring a tremendous amount of money into it, it really has hit the sewer. 200 billion into one financial organization alone, that is unreal. The US is regarded as beign 14% of the world economy, which is astounding in its self, so until it begins to rise, pull itself out of the gutters, we all are going to see a rough ride.

If I was DAAMIT, Nvidia and Intel I would push all releases out a little further, and ride each model for a little longer to make as much back as possible. And I suspect to some degree we will, how much and how long are any bodies guess, but its not looking any better in the near future.

Here's hopen all out friends here weather the storm well.

[Exmortis]

Originally Posted by CMetaphor

1. AM3 boards are all DDR3 only. Wrong actually, AM3 supports DDR3 and DDR2 RAM.

Any other questions?

Actually since DDR3 and DDR2 are not compatible with regards to pin outs, he is technicially correct. I have not seen nor heard of a hybrid design of a mobo that supports both. The memory controller on the AM3 chip supports DDR2 hence its backwards compatibility with AM2+ boards, but the doesn't mean you can put DDR2 memory on a AM3 socket board.

[superj]

Thanks, for the info.
The attainability of AMD BE chips is great.
If you were building a system today would you go with a cheap AM2+ board, and use some leftover DDR2 (from my Intel system). With the idea of upgrading to a new MB chipset when extra DDR3 RAM channels become available?

[CMetaphor]

Originally Posted by Exmortis

...but the doesn't mean you can put DDR2 memory on a AM3 socket board.

Says who? Both the new AM3 motherboards and their AM2+ counterparts are using the Exact Same Northbridge and there is very little difference between both versions from what I can tell... other than DDR3 vs DDR2 slots. So IMHO I think It would be possible...

[Exmortis]

Originally Posted by superj

Thanks, for the info.
The attainability of AMD BE chips is great.
If you were building a system today would you go with a cheap AM2+ board, and use some leftover DDR2 (from my Intel system). With the idea of upgrading to a new MB chipset when extra DDR3 RAM channels become available?

I would choose the board well. But budget demands what we pick, I really am happy with my M3A79T from ASUS but it is not the cheapest. I stay away from budget boards myself, since I usually have them for several CPU/GPU combos, so I feel personally that it is worth a few extra spacebucks.

[punk_zappa]

I am eyeing 720BE and Jetway HA07 Ultra. I can't afford Exmortis's board and DDR3 boards.