800MHz memory works only at 360MHz

[Montek]

I read somewhere that it seems to be normal and depends of FSB clock though i want to verify, i have AMD Sempron 3400+ and single slide of 800MHz DDR2 memory, and when i check in various tools memory frequency shows as 360MHz, is this normal, and was there point to go for 800Mhz memory if it works only at 360MHz anyway?

 

[JustaGeek]

360x2=720MHz - that's probably your speed now (Double data rate).

You might have to go into BIOS and change your Mem/FSB ratio, if you have that option.

 

[Montek]

Originally posted by: JustaGeek
360x2=720MHz - that's probably your speed now (Double data rate).

You might have to go into BIOS and change your Mem/FSB ratio, if you have that option.

Why x2 i don't understand, it probably would've shown it in CPU-Z or Everest the total output.

Besides i have just one plate, will increasing it to 2 and making dual channel increase frequency?

 

[JustaGeek]

It increases the bandwith dramatically, by about 50%, hence the increased performance.

You should always buy dual-channel memory in 2 module kit, though. They MUST be identical to work in dual channel configuration.

 

[Lord Banshee]

It is just how DDR works but seeing that your are using DDR2 it should be x4

DDR works with a clock that basicly does this over and over "01010101". SDR gets data every period ie "01". DDR gets data for every change to "0" and every change to "1". So you get twice the data for the same clock.

DDR2 clocks the "Bus" twice as fast as the clock so it can grab twice as much info from DDR with the same clock.

DDR-400 = 200MHz Mem and Bus clock = 200x2 = 400 Mil Data/sec
DDR2-800 = 200MHz Mem and 400MHz Bus Clock = 400x2 = 800 mil Data/sec

So my guess is you are looking at the Bus speed and it is under clocked a little. In the bios, like stated above, there are options to change the bus speed and the Mem speed ratios so if you want to make your ram do 400 than you need to change the ratio.

The above isn't all the detail but i hope it explains it enough. You can also find all the info you want:

http://en.wikipedia.org/wiki/DDR_SDRAM
http://en.wikipedia.org/wiki/DDR2_SDRAM

Now the dual channel has nothing to do with the speed of memory in terms of MHz.
The memory has 64-bits of data per slot. What dual channel does is allows 128-bits to come to the memory controller by using 64-bits from one Mem Stick and 64-bits from another effectively doubling the max bandwidth.

Have a look:
http://en.wikipedia.org/wiki/Dual-channel_architecture

 

[JustaGeek]

My FSB is 325MHz times 16/13 memory divider equals 400MHz memory bus for 800MHz memory speed.

I believe that DDR2 stands for the 2nd generation DDR memory, but correct me if I'm wrong.

 

[Montek]

Originally posted by: JustaGeek
It increases the bandwith dramatically, by about 50%, hence the increased performance.

You should always buy dual-channel memory in 2 module kit, though. They MUST be identical to work in dual channel configuration.

I don't really care about bandwidth because its for internet pc, not gaming.

Though I heard they don't have to be identical, though identical though this can decrease performance for like 20-30% sometimes.
What is problem if i buy non 2 kit module, of same memory, i believe they are same anyway even if you buy same memory after half of the year.

 

[Lord Banshee]

It is best to buy in 2-pack kits but as long as it is the same memory it should work. The kit just means it was tested to be exactly the same per spec.

 

[Montek]

There is setting
Timing Mode: Auto/Disabled.
When disabled you can set clock manually.
Memory Clock Value or Limit: 400-800 (set to 400 when timing mode set to - auto)
My question if its auto set to 400 it supposed to be like this and wont setting it to 800 will be over clocking?

 

[JustaGeek]

Originally posted by: Montek
There is setting
Timing Mode: Auto/Disabled.
When disabled you can set clock manually.
Memory Clock Value or Limit: 400-800 (set to 400 when timing mode set to - auto)
My question if its auto set to 400 it supposed to be like this and wont setting it to 800 will be over clocking?

It might be reading SPD as 400MHz - many manufacturers relax the frequencies/timings so some MB's can actually boot the first time.

Change it manually to 800MHz, set all the timings and voltage manually, too (e.g. 5-5-5-15-2T with subtimings on Auto).

Read the label - that's what the RAM is rated for.

 

[Montek]

I got bulk model of RAM, though i can check ram timings on internet, my mobo is from cheapest line it only has this settings, no timings allowed to set and few over clocking features.

Just set it to 800Mhz in bios, though its still showing as 360MHz at CPU-Z.
Over clocked my CPU to from 1800MHz to 2007Mhz and memory frequency rised to ~400Mhz.

I think i remember that frequency rises when you use dual channel configuration.