no 1866 ???

[LordSoth]

I have just got a new MSI MB 970A-46. now on there site it says the Mb is able to do 1866Hz speed ram, now i have just installed 8GIG 1866Hz corsair vengeance ram, but the Mb will not see it as 1866Hz. When i goto BIOS the fastest speed i can select is 1600Hz. Any ideas as to why the mainboard will not me select a faster speed etc. I do have the latest BIOS installed to(v1.6).

[IcE]

It's probably because of the CPU you have installed. Phenom II's for the most part don't play nice with RAM speeds higher than 1600 (and don't benefit from them either).

[Pill Monster]

They do benefit as long as the CPU/NB is raised accordingly...but yeah OP you'll need to raise the FSB to get past 1600mhz.

1800 is the highest I can go before my memory controller has a seizure

[IcE]

Originally Posted by Pill Monster

They do benefit as long as the CPU/NB is raised accordingly...but yeah OP you'll need to raise the FSB to get past 1600mhz.

1800 is the highest I can go before my memory controller has a seizure

To get the full benefit out of 1866 you'd have to have your NB clocked astronomically high. Over 3Ghz, which isn't happening without a Thuban.

[Pill Monster]

Originally Posted by ice445

To get the full benefit out of 1866 you'd have to have your NB clocked astronomically high. Over 3Ghz, which isn't happening without a Thuban.

Not really; the NB should be 3x your real memclock. So in my case 3x 900mhz = 2700mhz which is my current NB speed.

[LordSoth]

Nb = northbridge ???.

I uped my cpu/nb and it went spanners. So put it back to auto.

[IcE]

Originally Posted by Pill Monster

Not really; the NB should be 3x your real memclock. So in my case 3x 900mhz = 2700mhz which is my current NB speed.

I've heard different things from different parts of the net on what multiplier you should run the NB at. Got any sources? For the record I've seen the tables on overclockers and I'm curious as to where that calculation comes from (as I've seen others). An AMD official source would be nice but I can't seem to find anything

[deltatux]

Last check it was only when paired with an AMD FX processor is when you get DDR3-1866 support.

deltatux

[IcE]

Originally Posted by deltatux

Last check it was only when paired with an AMD FX processor is when you get DDR3-1866 support.

deltatux

This is correct and is why 1866 isn't selectable for the OP. There's a way around it if your up to some bus overclocking and if the IMC is up to scratch, but that's it.

[Pill Monster]

Originally Posted by ice445

I've heard different things from different parts of the net on what multiplier you should run the NB at. Got any sources? For the record I've seen the tables on overclockers and I'm curious as to where that calculation comes from (as I've seen others). An AMD official source would be nice but I can't seem to find anything

Ye of little faith...would I tell a lie?...
I can't remember it was something I read a couple of years ago - prob an AMD technical doc or maybe a Dragon overclocking guide.
Not sure what tables you mean either but 3x is the correct formula.


Here's the proof;

AM3 stock NB speed is 2000mhz, 2000mhz /3 = 666 (1333) - which is official max supported memory for AM3.

AM2+ stock NB is 1800mhz; 1800 /3 = 533 (1066) which again happens to be the official max supported memory for AM2+.


Another bit of FYI is that AM3 NB can be raised to 2400mhz without a voltage increase.
This is apparently by design in order to better support 1600mhz ram without a NB bottleneck... 2400 /3 = 800 (1600).

Edit-
I found a reference, it's stated in the Dragon Overclocking Guide released by AMD.

[IcE]

Originally Posted by Pill Monster

Ye of little faith...would I tell a lie?...
I can't remember it was something I read a couple of years ago - prob an AMD technical doc or maybe a Dragon overclocking guide.
Not sure what tables you mean either but 3x is the correct formula.


Here's the proof;

AM3 stock NB speed is 2000mhz, 2000mhz /3 = 666 (1333) - which is official max supported memory for AM3.

AM2+ stock NB is 1800mhz; 1800 /3 = 533 (1066) which again happens to be the official max supported memory for AM2+.


Another bit of FYI is that AM3 NB can be raised to 2400mhz without a voltage increase.
This is apparently by design in order to better support 1600mhz ram without a NB bottleneck... 2400 /3 = 800 (1600).

Edit-
I found a reference, it's stated in the Dragon Overclocking Guide released by AMD.

I've heard three and four as the ratio of actual ram speed to NB speed. But regardless of this, higher speeds are always better, correct?

Also it wasn't that I figured you were lying, I just wanted access to the actual source of what essentially amounts to rumors that I've been reading in forums.

Okay so according to the guide, the 3X ratio of CPUNB to actual memory speed is not a hard line ratio, but the minimum required. This at least says to me that 1600 speeds are probably still bottlenecked at 2400 and maybe even higher than that, although I suppose you'd need to test with benchmarks and a CPU that can do 3200mhz CPU-NB.

[Pill Monster]

Originally Posted by ice445

I've heard three and four as the ratio of actual ram speed to NB speed. But regardless of this, higher speeds are always better, correct?

Yep for sure.

Originally Posted by ice445

Also it wasn't that I figured you were lying, I just wanted access to the actual source of what essentially amounts to rumors that I've been reading in forums.

I was just giving you shlt....

Have a read thru this if you like, some parts are total crapola imo, like running DDR3 at 1.8v, but it has some good info nevertheless..
http://game.amd.com/us-en/content/pd...ning_Guide.pdf

[IcE]

Originally Posted by Pill Monster

Yep for sure.

I'm honestly curious of the bounds before the RAM stops being bottlenecked in any way by the integrated controller. I'm running 1333 right now but I have my NB at 2600 (which is close to 4X the base value). I guess I should test it but I'm too lazy right now. I have a hypothesis that having it at four times should do the trick.


Also with regards to the 1.85V RAM, very early DDR3 modules did exist that required those kind of volts.

[Pill Monster]

It won't be bottlenecked at 2600, if you were to raise your ram to 1600 right now you would see a marked improvement (in benchmark results at least).

At 2000mhz I'd say the imc will hold back your ram.

Increasing the NB just by itself to 2400 or more also has an impact on fps according to an Anandtech article I read ages ago.

[IcE]

Originally Posted by Pill Monster

It won't be bottlenecked at 2600, if you were to raise your ram to 1600 right now you would see a marked improvement (in benchmark results at least).

At 2000mhz I'd say the imc will hold back your ram.

The only issue I have with putting it back to 1600 is I'd need to go from 1.2V on the CPU-NB to 1.3V which I don't want to do given my cooler is at the limit already (and summer is just around the corner). I also have CL8 timings and 1T command rate so it shouldn't be too much faster.

[Pill Monster]

Originally Posted by ice445

The only issue I have with putting it back to 1600 is I'd need to go from 1.2V on the CPU-NB to 1.3V which I don't want to do given my cooler is at the limit already (and summer is just around the corner). I also have CL8 timings and 1T command rate so it shouldn't be too much faster.

dude I'm only using 1.075v for the nb - and that's at 1800mhz...

[IcE]

Originally Posted by Pill Monster

dude I'm only using 1.05v for the nb - and that's at 1800mhz...

Haha, yeah, that's because you have a brand new refined 955. I'm using an original C2 stepping one, the kind that guide was made for. 125W, not 95W.

I'm only using it in a Bulldozer board because my old 7 series one failed in an annoying way.

[bonob]

very usefull info here as i plan to buy a new mb and ram, mine serve me well but it start to have some strange behaviour with boot and oc ability.

[Paul L]

At least you may be able to tighten some of the latency settings of the ram if you run it
at 1600mHz.

[Rob McClelland]

This why you buy 1600mhz ram and start from 1333mhz my ram at 1539mhz with OC to 3220mhz. lol. Can't go higher then my multi player starts mess up pass 231mhz.

[IcE]

Originally Posted by Rob McClelland

This why you buy 1600mhz ram and start from 1333mhz my ram at 1539mhz with OC to 3220mhz. lol. Can't go higher then my multi player starts mess up pass 231mhz.

Why not put the RAM to 1066 to get higher?

[Rob McClelland]

Originally Posted by ice445

Why not put the RAM to 1066 to get higher?

ram be slow lol like I said multi player is mess up if I pass the 231mhz frontbus don't know why.