DDR, DDR2, DDR2 Dual channel 2x1GB=2GB??? aaargh!

[Pilotasso]

OK, since my current machine only supported simple DDR 400 RAM I had no trouble selecting modules.

 

However things changed since last time, and I may buy a new PC in the comming months and need some doubts clarified.

 

Wich CPU's support wich memory module types?

 

Dual channel modules are often quoted as 2X512MB or 2X1GB modules... I keep guessing what does 2X exactly means. Is it merely a redundant reminder its dual channel or does it indeed carry 2X1GB=2GB actual avaiable memory?

 

IS there any measurable perfomance difference in aplications between single and dual channel DDR2? Even on multi core processing?

 

Memory is realy expensive these days... geesh. 100€ for 1 GB DDR2 and twice that for DDR2 dual channel. I cant live without 2GB and my future machine will have 4GB=400€/800€ on memory alone!

[some1]

All new platforms (AMD's AM2 and Intel's 775) use DDR2 now. Although the difference in speed in MHz looks big compared to "old" DDR, the overall performance is quite the same, due to bigger latency.

 

Dual channel use two physical sticks of memory (2x512MB or 2x1GB and so on) which greatly improves read speed from memory (almost twice). So yes, 2x1GB = 2GB, but you need to have two free memory slots to insert them :) .The idea is similar to this used with hard disks and RAID 0. Generally speaking, to work in dual channel flawlessly both stick's should be from the same manufacturer, type, size, series etc. that's the reason why they are sold already paired. Of course you can try run two sticks not dedicated to dual channel in dual channel byt there are no guarantees that they will work.

 

About the performance. I made some tests with Lock On 1.12 and custom track I've made and the results are: (tests are with DDR, but DDR2 acts very similar)

 

Dual Channel:

2x512 without dual channel: 29.51 fps

2x512 with dual channel: 30.80 fps

 

Memory latency:

3-4-4-8-2T: 29.14 fps

2-3-2-6-1T: 30.80 fps

 

CPU speed (AMD 64):

1800MHz : 23.74 fps

2400MHz : 29.95 fps

2750MHz : 34.71 fps

 

So if you are short with money, better buy fast CPU and 2GB of cheap memory. :smilewink:

 

Ah, and remember, that due to technical limitations Windows XP 32 bit won't benefit fully from 4GB of memory. You'll need to buy Vista or Server 2003, or XP_64

[Pilotasso]

THx for your reply, needed that.

[Prophet]

Single channel has a 64bit bus.

 

Dual channel combines 2 channels to form a 128bit bus.

[Kuky]

and if you think DDR or DDRII memory is expensive... I can just remember how expensive RDRAM was, that thing was really a killer price wise, and damn it...still is very expensive! :angry:

[Pilotasso]

Just another quetion:

 

What is the memory speed on core Duo and AMD FX line today?

There seems to be a difference between the main bus and memory, and DDR2 modules come from 533 to 1066 MHz.

 

Mine is 400MHZ for memory and 1000MHz for hyper transport, but I would like to know the same for current and future chips.

 

I know that the base clock for such systems in 266MHz quad pumped or something like that. And memroy works with a multiplier for that frequence.

[Kuky]

Core 2 Duo's have Quad 266MHz FSB (1066MHz effective).

Matching memory for them is DDR2 PC4200, which is double rate 533MHz (1066MHz effective). You get higher memory only if you want to overclock.

 

Edit... the number after PCXXXX ie (PC4200) represents bandwidth in Gbps.

[walternowi]

The new budget version E4300 uses quad 200 MHz FSB. Should give you a higher overclock with budget memory.

 

Nowi

[Pilotasso]

Just one more question on this old thread:

 

Dual channel stick kits are much cheaper than 2 seperate single channel modules at 800MHz. Can I choose to run Dual channel memory in single channel to get the ttotal physical memory amount in the package? I.e. 2x1GB=2GB in single channel? Its set in Bios right?

[Kuky]

I haven't tried this so I can't confirm but I think you will need to run the DDR2 in dual channel mode, meaning you will place 2 sticks of 1GB (for total of 2GB) in RIMM 1 and 3 then if you want to expant you place next pair of sticks in RIMM 2 and 4.

 

You can try placing only stick in RIMM 1 and see if the PC boots... which I doubt it will.

[3Sqn_Fudd]

Pilotasso....

 

You'll be buying 2x1gig right? No worries, just put one in the first slot (looking from left to right) and another in the third and you'll be in dual channel... and there's no bios I have ever seen that sets single or dual channel. You may be thinking of 1t or 2t command rates

 

With the chip I know you plan on buying the overclock wont come into play much, the multiplier will be above 8 so you're fine. CPU speed is still king.

 

You're going with XP right?

 

Buying 2x1 gig sets isnt that much cheaper at all, the reason you want to do it though is that they're from the same binning process and matched accordingly...Prices keep falling... keep watch... and if i may suggest a source, this guy is usually all over what to get DDR2 wise.. Shop around...

http://www.xtremesystems.org/forums/showthread.php?t=124283

[Pilotasso]

THX Fudd but the question was rather if I can run the dual kit in single channel mode to make it 2 GB instead of 1GBX2 mode. Team ELITE Kits come super cheap here, almost as cheap as a single 1GB stick from other brands. And I would like to use them as if they were single channel to get 2 GB.

[Kuky]

running 2x1GB sticks in dual channel mode still gives 2GB of RAM :D

[Prophet]

Yeah I dont understand Pilotasso, you dont loose any RAM by running in Dual channel.

 

There is no benefit of single channel over dual.

[Pilotasso]

hmmm, I thought like doing RAID wich has 2 disks in paralel but you only get avaiable space equivalent of just one because all data is duplicated on both drives. I had the impression Dual channel was analogous (even if it works differently). Then there is no point going single channel for the current prices at all then. If i get 2 GB with better perfomance for the same amount of as with single channel memory all I have is advantages.

 

Thx for the answers Cheers!

[3Sqn_Fudd]

hmmm, I thought like doing RAID wich has 2 disks in paralel but you only get avaiable space equivalent of just one because all data is duplicated on both drives. I had the impression Dual channel was analogous (even if it works differently). Then there is no point going single channel for the current prices at all then. If i get 2 GB with better perfomance for the same amount of as with single channel memory all I have is advantages.

 

Thx for the answers Cheers!

 

 

Ahhhhh i see what you mean now... No, you get all the RAM, presuming you dont have some silly SPD problem. So the RAID (and indeed all HD's) allocation analogy doesn't apply to RAM.

 

Pilotasso, what are your sources to buy from? Just out of interest. Remember when we were talking about heatsinks, do you still have that link I sent you?

[Pilotasso]

I use local stores, Im a regular client of this one:

 

http://www.globaldata.pt/

Note TEAM ELITE double channel mem kits on promotion

 

Their component price list in PDF, perfectly readbale for all languages because its pretty self explanatory :)

http://www.globaldata.pt/tabelas/Componentes.pdf

 

I bought the heat sink on another place:

http://www.aquapc.com/loja/?id=1

 

Wich is where the heatsing from my current rig came from and possibly where the heatsink for my future system will be as well.

 

Bout the thread of the heat sinks, it was a long ago, cant remenber, will search for it. I thought about buying from amazon or something but with shipment costs it just doesnt compensate. All the local stores put up similar prices to that. Plus RMA is sweet with both stores, I go to the store and return home with replacement, if in stock. Never had a hitch and no questions asked safe for obvious user abuse visible.

 

EDIT: found a link you gave, it was for a PC case, I found no heatsink links from you.

[Kuky]

Well actually even in RAID0 mode you still don't loose any HDD space. If you set 2 HDD of 250GB in RAID0 mode (Stripping mode) you still see 500GB HDD space. It is only RAID1 (Mirroring mode) that you have 250GB of HDD space because the second HDD is used for backup only and has everything duplicated from first HDD.

[Pilotasso]

then how does it work?

[Roi Danton]

http://en.wikipedia.org/wiki/Dual-channel_architecture