how does 3Gb work in dual-channel?

snadge

snadge

snadge

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ive benen told (which I believe to be wrong) that a laptop running a 1Gb stick and 2Gb stick will run Dual-Channel up to 2Gb and single channel over that?

rubbish surely?

Dual-Channel is setup at POST and either works fully or not at all

can anyone clear this up for me? i cant see why laptop or PC manufacturers do this as memory is cheap as chips and they are just disabling the speed of computer memory by half to save pennies.. as you know advertised DDR speeds only work when you have 2 sticks running at dual-channel... so laptops (or PC's) wit 3Gb of DDR 1066Mhz RAM will only be running at 533Mhz in single channel mode - doesnt make any sense to me to put 3Gb in any machine.. should be 2x1, 2x2 OR 2x4 ..never 2+1

the reason I ask is a friend has just bought a laptop really good deal, £249 for dual-core westmere Pentium 2.2Ghz with 667Mhz onboard GFX, 3Gb DDR3 1066Mhz memory, 250Gb HDD, wireless-N, Gigabit Ethernet, windows 7 64-bit and webroot security essentials free

ive told him the memory will only run at 533Mhz in single channel mode and if it were my I would spend £12 on a 2Gb stick to replace the 1Gb stick with giving him 4Gb and 1066Mhz

whats others thoughts on this?

thanks
 
You're wrong about the RAM speed.

DDR3 1066MHz will run at that speed if it's in dual or single channel.

What you miss out on with single channel is the ability of the memory controller to simultaneously access both banks of RAM.

I suppose manufacturers use 3GB because every pound counts when they're trying to compete and if a 32 bit operating system is used a large part of the fourth Gibabyte isn't utilised.
 
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im not saying double channel means its twice as fast as stated speed... i was told that its called DOUBLE DATA RATE because it uses dual-channel to get its qouted speeds and thus 1066Mhz is only that if its running dual-channel with two identical sticks
 
...also my dads laptop has 1066Mhz ram in but CPUZ states it runs at 533Mhz... i have my friends laptop here and im yet to turn it on..I will check it..but im running into more problems with my dads DVD drive now which wont respond when set to boot from CD and power on - but works in windows
 
you are mixing up terms there.

Double data rate is a term that's been carried on from the original DDR-SDRAM. Double data rate referred the ram's ability to transfer twice the information per clock cycle compared to SDRAM.

Dual Channel refers to the memory controller in the cpu/motherboard being able to access two sticks at once, in a nut shell.

So, if the ram is rated at 1066mhz then that is what it will run at, regardless of the memory configuration (as long as the motherboard supports it)

snadge said:
...also my dads laptop has 1066Mhz ram in but CPUZ states it runs at 533Mhz... i have my friends laptop here and im yet to turn it on..I will check it..but im running into more problems with my dads DVD drive now which wont respond when set to boot from CD and power on - but works in windows
Click to expand...

yes. 533mhz is the physical speed. 1066 is the effective speed when taking double date rate in to account.
 
snadge said:
im not saying double channel means its twice as fast as stated speed... i was told that its called DOUBLE DATA RATE because it uses dual-channel to get its qouted speeds and thus 1066Mhz is only that if its running dual-channel with two identical sticks
Click to expand...

snadge said:
...also my dads laptop has 1066Mhz ram in but CPUZ states it runs at 533Mhz... i have my friends laptop here and im yet to turn it on..I will check it..but im running into more problems with my dads DVD drive now which wont respond when set to boot from CD and power on - but works in windows
Click to expand...

Double Data Rate and Dual Channel are two completely different things.

Double data rate means that the effective RAM speed is doubled so 533MHz is 1066MHz effective.

My RAM is 1600MHz and it showd in CPU-Z as 800MHz and dual channel.
 
ahh i see - i asked about it on techguy not long ago and someone told me that Dual-Channel would work at all under 2+1 config - i mentioned my speed theory there and this wasnt mentioned...between a few people on the thread... so assumed it was correct, cant remember who told me that you only get the effective speed in dual-channel, perhaps I picked it up wrongly, also seeing half the speeds for each stick in CPU-Z led me to believe this - for e.g. my 667Mhz ram shows a 333Mhz per stick and thats why I thought that.

im glad thats been cleared up, thanks :)

so... does dual-channel work in 2+1 configs? if so how?
 
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