Integrated Memory Controllers

Aaron

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INEGRATED MEMORY CONTROLLERS - CHANGING THE DEPENDENCIES OF COMPUTING

An IMC is the memory controller hub of a chipset integrated into a CPU.  MCHs control the operation of memory.

AMD was the first (for performance reasons) to have an on-die memory controller back in 2003, with the Athlon 64 [Sledgehammer] generation of CPUs.  Since then, the IMC has been carried from generation to generation, and eventually adopted by Intel in the Core i7 [Nehalem] generation of CPUs.

Since the IMC's integration, many believe there isn't a northbridge on mainboards.  No MCH doesn't mean there is no northbridge on the board.  The northbridge is the chip on the north of the board, the southbridge is the chip on the south.  Simple.

Before IMCs, a computer diagram looked like this:




Can you see how the memory is interconnected with the NB?  This causes data transfer to take longer with higher latency [delay].  But the board is responsible for the well-being of this MCH.


IMCs IN MODERN SYSTEMS:

INTEL CORE I7



In the Nehalem generation of CPUs, Intel moved the MCH [Memory Controller Hub] into the CPU.  It's tri-channel, and supports up to DDR-1333, respectively.  Going over these speeds is overclocking; which is never guaranteed.

Note how the NB is still present, but now only serves PCI-E functions.


INTEL CORE I5



Intel has given more of the NB's [IOH's] functions to the CPU.  In this case:  PCI-E.  The supported PCI-E configurations are x16/x0 and x8/x8.

As you can also see, the legacy southbridge (ICHx) has now disappeared too.


AMD PHENOM II, ATHLON 64 (AM2+/AM3)



Phenom II's dual channel DDR2/DDR3 controller supports DDR-1066 on DDR2, and DDR-1333 on DDR3, respectively.  Going over these speeds is overclocking; which is never guaranteed.


Can you see how the memory is interconnected with the CPU, and not the NB as in previous generations?  This is the big change which allows those massive bandwidth figures, and ultra-low latency times.

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GETTING DECENT DDR2/DDR3 SPEEDS

On DDR2/DDR3, when you go beyond about 1000 MHz with DDR2 and 1333 MHz with DDR3, there's a special thing you need to do.  Most people only set CAS, tRCD, tRP and tRAS to the specified timings.  While this is necessary, it is also not enough.  If you're using a chipset that supports EPP/XMP, I suggest you use these profiles because the advanced memory timings will be applied.  When overclocking, the advanced timings are not changed, and usually cause unstable overclocks.

The timing you need to start working with is tRFC.  tRFC can go as high as 72T when you go to 1800 MHz.  Download Everest, view your SPD profile, and make note of the tRFC setting in your sticks EPP/XMP profiles if you wish to overclock manually.  If no EPP/XMP profiles are present, unfortunately, you will have to guess.

<hr>

Thanks for reading.
 

Fredrik

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Thank you! But what does a memory controller really do? Check for Alf Helmer's disease? You know, the problem when you can't remember names and stuff.
 

Aaron

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Shall add that in, Fredrik. :biggthumbsup:  Never thought of the simple things. :lol_anim:
 

HU16E

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Simple & understandable IMC presentation Aaron. Currently, not counting possible future revision changes, according to Intel, the i7 920 C0 & D0, 940 C0, & 950 D0, still only natively support 800/1066 speeds. The 965 C0 & 975 D0 however, will both support up to 1333 speed.
 

Aaron

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The "respectively" basically means I don't have to be specific. ;) :lol_anim:

I want to keep this as simple as possible, by trying to say more words and less numbers.
 

ex_forum_user_3

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Phenom II's dual channel DDR2/DDR3 controller supports DDR-1066 on DDR2, and DDR-1333 on DDR3, respectively
Certified only to do the max speeds with 2 ranks memory per channel.
This is:

2 single sided memory sticks per channel

or

1 dual sided memory stick per channel

This is for all AMD's, however, it depends on the memory controller inside the CPU how fast the max speed is.
 

Stu

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When purchasing memory, don't bother buying 'triple-channel' kits if you have an AMD system, they are only for use in Intel i7 systems. You want 'dual-channel' kits for AMD systems. ;)
 

Panther57

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This is a valuable topic with all the mismatched new build memory issues and OC's over 1066/1333 that we all can use some informative education.
Thanks
 

raisethe3

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I heard that the new Phenom II 965BE C3 will have support for  4 sticks of DDR3 1333Mhz memory.  Sounds like a good thing to me!  :shocked_anim:  Instead of being stuck with 2 sticks all the time.

Source: 
http://www.pcstats.com/NewsView.cfm?NewsID=79803
What do you guys think?  Is it a good thing? 
 

ex_forum_user_3

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Raisethe3, finally!!:

The other minor change is better support for four sticks of DDR3-1333 RAM.
About time they did.
However, knowing AMD, it will probably support 2x1600 unofficial ofcourse :bonk:
 

raisethe3

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Or 2133Mhz if you overclock and get it down and dirty (via the MSI 790FX-GD70), but 2 sticks though.

Bas said:
Raisethe3, finally!!:

About time they did.
However, knowing AMD, it will probably support 2x1600 unofficial ofcourse :bonk:
 
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