Socket AM2 Forward Compatible With AM3 CPUs

[onethreehill]

"AMD has released details of its next-generation desktop CPU interface, Socket AM3, to its OEM partners. In a mildly surprising move, AMD has revealed that AM2 will accept AM2 or AM3 CPU packages. Additionally, recent roadmaps have confirmed that AM3, AMD's upcoming desktop CPU socket, will not be backwards compatible with AM2-package CPUs. Roadmaps and memos have also confirmed that this AM3 package will be for AMD's "K8L" architecture, and not for the upcoming 65nm AM2 Brisbane CPUs scheduled for launch this December."

http://www.dailytech.com/article.aspx?newsid=3169

A Visual Representation Of Compatability (Courtesy of JuanFlaiter)

http://img155.imageshack.us/img155/6440/am33gg.png

[nn_step]

And who said It first :D

[LOE]

hahaha quad damage

get some :)

So if the rumor on rev HT turns out to be true I'm updating my cluster to am2 chips, then rev g and then K8L right?

It is strange thou... am2 supports am3 chips, but am3 doesn't support am2

[Otaking71]

hahaha quad damage

get some :)

So if the rumor on rev HT turns out to be true I'm updating my cluster to am2 chips, then rev g and then K8L right?

It is strange thou... am2 supports am3 chips, but am3 doesn't support am2

my guess would be am3 has 4 ht links..and am2 has 3.....the 4th must be active to use that socket?

[nn_step]

hahaha quad damage

get some :)

So if the rumor on rev HT turns out to be true I'm updating my cluster to am2 chips, then rev g and then K8L right?

It is strange thou... am2 supports am3 chips, but am3 doesn't support am2
Actually that was done because Am2's DDR3 memory controller is bodgy.
And has issues at 1600+Mhz speeds. SO to truely make sure the best performance possible. AMD is going to include the improved Memory controller in AM3 but not put it into AM2 because it will even farther expand the Memory controller and they are trying to keep the chip size down.

[mursaat]

Actually that was done because Am2's DDR3 memory controller is bodgy.
And has issues at 1600+Mhz speeds. SO to truely make sure the best performance possible. AMD is going to include the improved Memory controller in AM3 but not put it into AM2 because it will even farther expand the Memory controller and they are trying to keep the chip size down.Let me get this straight, before the thread becomes in another rumour flood:

Basically AM2 is K8L compatible but somehow crippled because of the AM2 DDR3 memory controller. Isn't the memory controller on the chips? How's AMD is going to include the improved Mem controller on AM3 but not AM2 if the mem controller is on the chips? Maybe you meant AM2 cpus and AM3 cpus.

[VulgarHandle]

k8l on am2 alone justifies current am2 systems

think we can merge this in perkam's thread, and have him update first post :D

[JuanFlaiter]

And who said It first :D

:clap: :clap: :clap:

nn´s prophecy starts to make sense.

I wrote a column back on march about the AM2 being a transition socket and nobody trusted me.

[LOE]

now if only nn could speed time up cause I can't wait to get K8L :)

[informal]

Cheers to nn_step for being the first to say it(about mem. controler supporting DDR3 and AM2 compatib. with K8L),and to all of us who kept saying that K8L will go to AM2.Now where is that gOJDO guy:D .

Anyho,Perki my man,be sure to update that first post in info thread,we don't want anymore xtreeme members loosing faith in AMD,do we :D?

[einCe]

Woohooooooooo

[onewingedangel]

just because the am2 socket is compatable theboards may not be.

AM2 cpu's have only a ddr2 memory controller, and the boards only support ddr2 dimms.

What this may mean is that am3 will feature the same physical pin layout (but not neccesarily used the same)and may have mc support for ddr2 or ddr3 - plug into am2 board for use with ddr2 or into a am3 board for use with ddr3.

AM2 cpus and motherboards work only with ddr2.

am2's memory controller has never had ddr3 support, that was just nn steps usual tactic of throwing mud and hoping something sticks - and even then changing what he 'said' - from am2 using ddr3 at launch becoming am2 having ddr3 support that must be 'disabled'.

Essentially I think k8l will be backwards compatable with the older socket, albeit not be pushed to its potential (less ht links, ddr3 support, and possibly memory channels)

[LOE]

with only dual core ddr3 wont matter that much - k8 is not taking a big advantage from bandwidth

[Cybercat]

Does K8L support both DDR2 and DDR3 then? :confused:

[Thorry]

Does K8L support both DDR2 and DDR3 then? :confused:

Well yes and no.

As you know the memory controller AMD designed for DDR2 is designed in such a way that DDR3 support can be added easily. The interface to the memory controller for the CPU is exactly the same.

If AMD want they can release DDR2 K8L CPUs, but then there have to be motherboards supporting it so AMD will talk with mobo producers about that.

It won't support both DDR2 and DDR3 on one motherboard, you have to chose before.

[Cybercat]

As you know the memory controller AMD designed for DDR2 is designed in such a way that DDR3 support can be added easily. The interface to the memory controller for the CPU is exactly the same.Actually I didn't know that. :p: Interesting...

If AMD want they can release DDR2 K8L CPUs, but then there have to be motherboards supporting it so AMD will talk with mobo producers about that.could it be as simple as a BIOS update for current boards?

[LowRun]

am2's memory controller has never had ddr3 support, that was just nn steps usual tactic of throwing mud and hoping something sticks - and even then changing what he 'said' - from am2 using ddr3 at launch becoming am2 having ddr3 support that must be 'disabled'.


QFT ;)

[perkam]

AMD has revealed that AM2 will accept AM2 or AM3 CPU packages.That basically means Socket AM2 will accept AM2 and AM3 CPUs.

This doesn't CONFIRM that k8-l mem controller would have to be compatible with both ddr2 and ddr3.

Socket AM3 will initially be ddr2 and then move on to ddr3 ONLY when DDR3 hits mass retail.

That won't happen by q3 2007, so lets stop dreaming about ddr3 right now.

Perkam

[dinos22]

And who said It first :D
so that court decision was favourable....... ;)

[cky2k6]

in the simplest terms possible, i think what this all means is that am3 will be able to run ddr2 and ddr3, so it can still use am2 boards, but am2 does not support ddr3 and therefore cannot be used in a am3 board.

[freecableguy]

And who said It first :D

Ahem, get fixxxer in here with his signature quote.....then we can see who said it first. :D

[STEvil]

My guess:

AM2 works with DDR2 (and DDR3 but limited and likely disabled in retail)
AM2 works with AM2 boards.
AM3 works with DDR3 (and DDR2 but limited and likely disabled in retail)
AM3 works with AM2 and AM3 boards.

*adds 2 cookies to the pot*

[[XC] leviathan18]

lol i won 2 cookies :p:

[LOE]

it all depends on price/performance of ddr3

if the cpu is not data hungry there will be many am3 chips with ddr2

yeah the top notch might not be welcome in this forum, but overall demand is driving the industry, so if am3+dd2 is a goog combo it will be adopted

[VulgarHandle]

My guess:

AM2 works with DDR2 (and DDR3 but limited and likely disabled in retail)
AM2 works with AM2 boards.
AM3 works with DDR3 (and DDR2 but limited and likely disabled in retail)
AM3 works with AM2 and AM3 boards.

*adds 2 cookies to the pot*

umm, i don't think DDR2 will be limited or disabled on AM3 cpu's....why? because they're gonna work on AM2 boards...

[JuanFlaiter]

Ok kids, just like in kindergarden

http://img155.imageshack.us/img155/6440/am33gg.png

[Lightman]

Ok kids, just like in kindergarden

http://img155.imageshack.us/img155/6440/am33gg.png

Brilliant!!

Now who is thinking that Socket F is already compatibile with K8L and almost for sure with HT3.0??

[LOE]

socket F has much more pins

[gOJDO]

Cheers to nn_step for being the first to say it(about mem. controler supporting DDR3 and AM2 compatib. with K8L),and to all of us who kept saying that K8L will go to AM2.Now where is that gOJDO guy:D .

Anyho,Perki my man,be sure to update that first post in info thread,we don't want anymore xtreeme members loosing faith in AMD,do we :D?
Here it is the gOJDO guy, but you seems that you've misunderstood the whole article:
1. DDR3 is not compatible with AM2
2. chips with DDR3 IMC might be compatible with DDR2 memory

http://www.xtremesystems.org/forums/showpost.php?p=1554623&postcount=42
No, there will be incompatibility. No matter that DDR2/DDR3 are pin compatible, they are not DATA compatible. The DDR3 sends 8 bits per clock per line, while the DDR2 sends only 4. DDR3 requires new MC. It is possible to make the DDR3 MC to work as DDR2 but not vice versa. The K8-DDR2 will not work with DDR3, and I don't know if the K8-DDR3 will work with DDR2.
If we make an retrospective, the only difference between the s754(64bit IMC) and the s939(128bit IMC) is the number of DDR channels. By the logic, there was no need for s939. They could make the new mainboards to have option to enable/disable the second memory channel, depends on the CPU type(that could be single or dual channel IMC). It is complicated, and thats why the DDR3 will come on new socket, just like the K8 with 128bit IMC(with pin compatibility) came on new socket.

[`odin]

Ahem, get fixxxer in here with his signature quote.....then we can see who said it first. :D
i will notice it the first when you suddenly change into an amd fanboy again..;)

[perkam]

Ok kids, just like in kindergarden

http://img155.imageshack.us/img155/6440/am33gg.pngGreat work Juan :)

Added to first post :)

Perkam

[ZX7891]

Even if AM3 cpu's work on AM2 boards, woudlnt the cpu be crippled by ddr2?

[gOJDO]

Even if AM3 cpu's work on AM2 boards, woudlnt the cpu be crippled by ddr2?
yes. The K8L will be quadcore design, and each core will have higher IPC. It will be much more bandwidth hungry, so the shared L3 will buy some to reduce RAM accesses and latency. But even with shared L3, I think that the two channels of DDR2 will be not enough to "feed the beast"(2 x cores with lets guess 1.5 x IPC). Unfortunatly there will be dualcore K8L, so DDR2 makes sence to provide enough bandwidth. Good for those who have good sAM2 mainboards.

[DilTech]

There's also quad-core K8L, seeing as how K8L is natively designed from the ground up for quad-core, but can likely scale muchhhhhh higher than that.

For that one, I'd be curious on the multi-threaded performance differential between DDR2 and DDR3.

[Lightman]

K8L on DDR2 should preform (memory wise) better than Intel Kentsfield thanks to IMC. Of course platform of choice for K8L will be AM3. Difference in preformance can be similar to S754/S939.

[gOJDO]

K8L on DDR2 should preform (memory wise) better than Intel Kentsfield thanks to IMC.
Wrong! We don't know if K8L will perform better (memory wise) than Kentsfield. But if it does, then it will be not becouse of the IMC. It will be becouse of the shared L3 and the OOO L/S execution.
Of course platform of choice for K8L will be AM3. Difference in preformance can be similar to S754/S939.
We can't say that right now becouse we don't know what features K8L will include and how bandwidth hungry it will be. I guess that there will be difference in the performance boost between dualcore and quadcore, when switching from DDR2 to DDR3.

[nn_step]

Even if AM3 cpu's work on AM2 boards, woudlnt the cpu be crippled by ddr2?
Honestly it will not be for another 9-18 months before really good DDR3 starts coming out. Until them only a handful of ES are actually vastly superior to DDR2.
So for right now. little is lost. but shortly A hell of alot will be gained.

[`odin]

Honestly it will not be for another 9-18 months before really good DDR3 starts coming out. Until them only a handful of ES are actually vastly superior to DDR2.
So for right now. little is lost. but shortly A hell of alot will be gained.
the spamfairy has spoken again :)

*rofl*

[informal]

Here it is the gOJDO guy, but you seems that you've misunderstood the whole article:
1. DDR3 is not compatible with AM2
2. chips with DDR3 IMC might be compatible with DDR2 memory

http://www.xtremesystems.org/forums/showpost.php?p=1554623&postcount=42


Just reread what i've said...I understood it well.I said :
(about mem. controler supporting DDR3 and AM2 compatib. with K8L)

This means : K8L supports DDR3(and DDR2 when combined with AM2) AND AM2..Seems i have to draw pictures for some

[gOJDO]

Just reread what i've said...I understood it well.I said :


This means : K8L supports DDR3(and DDR2 when combined with AM2) AND AM2..Seems i have to draw pictures for some
you can draw pictures for your self, but it will not give you any vision. you were calling "the gOJDO guy". lets hear why?

[informal]

you can draw pictures for your self, but it will not give you any vision. you were calling "the gOJDO guy". lets hear why?

Relax,I 've said it that way 'cos you were saying that K8L is not AM2 compatible.Simple as that.

[gOJDO]

I never said that K8L is not sAM2 compatible, but I was meaning it becouse as far as we know K8L will come with DirectConnectArchitecture2 and DDR3 IMC. It sounded stupid to me that sAM2 mainboard will be designed to support better FSB(HTT3) that will come after 2 years and was also stupid for me to belive that the K8L will use DDR2 becouse it is a quadcore design and it has higher IPC per core. What I've said is to forget sAM2 & DDR3 which is true and
there will be no K8L with DDR2 and HTT2 which is also true becouse K8L will have DDR3 and HTT3.

http://www.xtremesystems.org/forums/showpost.php?p=1554207&postcount=24
I understand what you've said. I was talking about what you think that "killer" architecture will be. The "killer" will be K8L compared to K8, as it really appears on papers. DC or DC2; HTT, HTT2, HTT3 or FSB really means NOTHING about desktop/2P workstations. It has role only for servers and offers better SMP scalling. Also, DC2 is not changing the architecture of the CPU(it remains with the same IPC, same fetchers, decoders, execution units, and etc). DC2 changes the interconnects and the memory interface. New memory interface means new socket for K8(IMC sometimes sux). Forget about sAM2 & DDR3. DC2 will come with K8L and there will be no K8L with HTT2 & DDR2.

[informal]

What I've said is to forget sAM2 & DDR3 which is true and
there will be no K8L with DDR2 and HTT2 which is also true becouse K8L will have DDR3 and HTT3.

Well ,nobody ever expected to see K8L on AM2 board with DDR3 memory.That was quite obvious.

And BTW,how can you say that there will be no K8L with DDR2 and HTT2???That was exactly the way how K8L will work in AM2 boards(with HTT2 and DDR2 "mod",since the controler is supporting both memory standards,and the chip is backward compatible in terms of HyperTransport)

[Lightman]

Wrong! We don't know if K8L will perform better (memory wise) than Kentsfield. But if it does, then it will be not becouse of the IMC. It will be becouse of the shared L3 and the OOO L/S execution.

We can't say that right now becouse we don't know what features K8L will include and how bandwidth hungry it will be. I guess that there will be difference in the performance boost between dualcore and quadcore, when switching from DDR2 to DDR3.

We know! You can find few posts about Kentsfield showing memory preformance (not cache! i never mention CACHE) and even contemporary AM2 CPU preform better.

PS. READ AND UNDERSTAND!
I know that sometimes people like WAR! I prefer BRAINSTORMS.

[gOJDO]

Well ,nobody ever expected to see K8L on AM2 board with DDR3 memory.That was quite obvious.
To some quite obvious, to others not.

And BTW,how can you say that there will be no K8L with DDR2 and HTT2???That was exactly the way how K8L will work in AM2 boards(with HTT2 and DDR2 "mod",since the controler is supporting both memory standards,and the chip is backward compatible in terms of HyperTransport)
Becouse of backwards compatibility it will work, but it will not have DDR2 IMC and HTT2 FSB.
You failed to "own" me on this like you were meaning "and to all of us who kept saying that K8L will go to AM2.Now where is that gOJDO guy".

[gOJDO]

We know! You can find few posts about Kentsfield showing memory preformance (not cache! i never mention CACHE) and even contemporary AM2 CPU preform better.
I thought you are talking about the procesors memory system(L1-L2-(L3)-RAM), not about their memory contrllers and RAM bandwidth/latency performance. Kentsfield has no integrated memory controler, it may use multichanel FB-DIMM/DDR3/XDR with another chipset and to have much better MC<->RAM performance.

PS. READ AND UNDERSTAND!
I know that sometimes people like WAR! I prefer BRAINSTORMS.
Yes sir, as you wish.

[informal]

To some quite obvious, to others not.


Becouse of backwards compatibility it will work, but it will not have DDR2 IMC and HTT2 FSB.
You failed to "own" me on this like you were meaning "and to all of us who kept saying that K8L will go to AM2.Now where is that gOJDO guy".


Yes and how do you expect K8L to work in AM2 mobos with DDR2 memory if it don't have DDR2 compliant mem. controler???
And BTW,HTT is not a FSB...It should be clear to you...Or maybe not.

[gOJDO]

Yes and how do you expect K8L to work in AM2 mobos with DDR2 memory if it don't have DDR2 compliant mem. controler???
Dude, stop looking after something to "own" me, turning the things like you want. I never said K8L can work without DDR2 support on the IMC, I said that DDR3 IMC is possible to work with DDR2 RAM.
And BTW,HTT is not a FSB...It should be clear to you...Or maybe not.HTT is used as front side bus(FSB) to connect CPU with northrbidge.

[informal]

Man i just quoted what you said,nothing more(i even bolded out).
Again,back out a bit and reread about HTT.It's nothing like a FSB and it's a mistake to call HTT that way.Yes it's used instead of FSB in AMD's(and others in DirectConnect consortium) case and it's a massive difference between them(AMD) and intel.

[gOJDO]

Again,back out a bit and reread about HTT.It's nothing like a FSB and it's a mistake to call HTT that way.Yes it's used instead of FSB in AMD's(and others in DirectConnect consortium) case and it's a massive difference between them(AMD) and intel.

http://www.amd.com/us-en/Glossary/0,,238_242~1039,00.html
Frontside Bus - (FSB).
The primary bus interface that connects a microprocessor to other system devices via the Northbridge system chipset. Typically, it allows the processor to communicate with main memory (RAM), the system chipset, PCI devices, the AGP card, and other peripheral buses. It also connects to the Level 2 cache unless the processor has a backside bus.
Is HTT used as a primary bus interface that conects a microprocessor(CPU) to other system devices(PCI, AGP/PCIe and other peripheral buses) ?
If yes, than it is used as FSB, not instead of FSB.
It sounded stupid to me that sAM2 mainboard will be designed to support better FSB(HTT3)

[largon]

via the Northbridge system chipsetNorthbridge = MC + AGP ctrl -> no A64 uses a NB, A64 chipsets are southbridges / MCPs.

Technically HTT is not a front side bus since it doesn't connect CPU to main memory. It also connects to the Level 2 cache unless the processor has a backside bus.Backside bus is used only with external caches, this doc appears to be composed when K6-2 was the most advanced thing from AMD. (source material from this millenia would be nice)

Afterall, HyperTransport bus is a universal bus standard of which's uses aren't limited in any way to PC hardware. Thus HyperTransport bus is used instead of a FSB. HT bus does perform similar tasks as FSB, but it's not exactly a FSB.