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Confusion reigns... Athlon 64 use Dual Channel RAM ?

By Henner
Jan 8, 2006
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  1. Hi ! I'm a greenhorn in need of advice ..
    Have an Athlon 64 3400+ 2.4Ghz with Asus K8S-LA which I understand is capable of supporting 2GB of PC3200 DDR SDRAM in two slots. It currently has only one 512MB DIMM installed, and I'd like to remove that and max out with 2 x 1GB. I am under the impression, perhaps incorrectly, that DDR (dual data rate) is not the same as Dual Channel, and dual channel modules can not be used, and/or not supported in an Athlon 64.
    I've searched and read for hours and days and can't find an authoritative answer to the dilemma. Some dealers advertise PC3200 DDR , but the fine print always says they are designed for Dual Channel. The manufacturer sites aren't any help either, as their wordings are often misleading.
    Can Dual Channel modules be used safely without crashing the system ? If not, can someone direct me to a manufacturer that suppies modules for this rig without the dual chanel hype ?
    With tongue-in-cheek I ask: Will someone please explain or tell me where to go ? THanks in advance for your help.
     
  2. Vaerilis

    Vaerilis TS Rookie Posts: 64

    Dual channel mode is used when two or four almost identical modules "work together" faster. The performance increase is significant for Pentium 4 systems, but only slight for A64 systems.

    DDR means double data rate. There are no dual channel modules, just DDR ones. Dual channel mode is a feature, a technology, not a memory type.

    To sum things up: any identical pair of DDR memory modules can run in dual channel mode, giving a very slight increase in performance on A64 platforms. Any non-identical pair of memory modules (or just one module) will run in single channel mode, resulting in a bit inferior performance. It's really irrelevant in your case.

    Feel free to buy any kind of PC3200 DDR SDRAM. There are no bad choices if you just want to use it casually (without overclocking), as long as you don't get something no-name.
    There are lots of trustworthy brands: Corsair, Mushkin, Kingston, A-data, Twinmos, Patriot...

    Anything on this list at Newegg would be a good choice for casual use, except the few "registered" modules at the end. Registered memory is not what you need, only a few motherboards require it.
     
  3. Henner

    Henner TS Rookie Topic Starter

    Vaerilis,
    Thanks for the quick response. I've taken a look at the reference you gave for Newegg and note that many of the listings do in fact specify Dual Channel.
    The following is taken from one of the many reports I've read, and one that lead me to the conclusion that DDR and dual channel are different:
    " To use DDR Dual Channel configuration in order to achieve the maximum performance your CPU is capable of giving you, you will need a motherboard with this feature and two identical memory modules.

    There is one exception, though: the Athlon 64 processor. On this processor family the memory controller is embbeded in the CPU, not in the chipset. Therefore with this CPU the use of DDR Dual Channel configuration depends on the CPU, not on the motherboard. Socket 754 Athlon 64 processors aren't capable of this configuration. So if you have this kind of CPU you can't use DDR Dual Channel. Socket 939 Athlon 64 processors have an embbeded Dual Channel memory controller, thus allowing this processor to use this configuration. The installation steps are the same for other kinds of processors, as we will explain below."


    Since I have a Socket 754 system I concluded that DDR and Dual Channel are different. Am I wrong ?
     
  4. Vaerilis

    Vaerilis TS Rookie Posts: 64

    That means your chipset doesn't support dual channel.
    You can use any memory modules, but they will run in single channel mode. It doesn't really matter.
    Just to make things clear: DDR is a memory type (like SDR, DDR-II, or RDRAM), and dual channel is a technology (like hyperthreading, hypertransport...).
     
  5. Sharkfood

    Sharkfood TS Guru Posts: 1,198

    Hi Henner,
    As already mentioned, Dual-Channel has nothing to do with the memory.. but the mainboard.

    Dual-Channel is just a "trick" of allocating two identical sized banks of memory into two channels which can effectively double the transfer rate. The memories themselves are just standard DDR memory.

    DDR memory advertised as "Dual-Channel" only means they are of high quality, been tested as such and can endure the extra load this may pose. In actuality, they are just standard, everyday DDR memories...ensured to be identical for best results when running in Dual-Channel mode.
     
  6. Henner

    Henner TS Rookie Topic Starter

    Thanks guys for the information.
    Guess I now have to decide which is the best quality for the money.
     
  7. fury

    fury TS Rookie Posts: 38

    I've always had a good experience with Crucial (Micron) and Corsair. Any stick from them is a good buy.

    If you want the ultimate in performance, make sure the stick(s) you get is rated for CAS Latency 2 (CL2 or CAS2 as it might commonly be referred to). This refers to how quickly a column of the memory can be accessed when an instruction is sent (correct me if I'm wrong) so the lower this number, the better the memory. Be aware, though, that this can sometimes come at a premium. If you're budget-minded, a CL3 part from a quality brand name manufacturer is better than a CL2 part from a generic manufacturer.
     
  8. Henner

    Henner TS Rookie Topic Starter

    Thanks Fury.
    Once again I've been doing a lot of looking and reading to sort through all the options out there, and you've hit on my next question regarding Latency. Since my system is apparently incapable of Dual Channel operation, will a lower latency really impact the performance that much ?

    I'm not into serious gaming, and I have yet to learn what overclocking is, so that can wait for another day.
    But I do use my system as a flight simulator, and noticed a vast improvement in response and graphics when I retired my old system and bought this. I've used several manufacturer's memory configurators and more often than not, they come up empty. Some sites don't even show my SR1550NX.... not that they should, but it would be helpful I guess ?
     
  9. Merc14

    Merc14 TS Rookie Posts: 464

    Henner-
    Your CPU, like all AMD 64's, has the memory controller on the CPU itself, not the FSB. This gives you the very high throughput to RAM that AMD's are famous for. There are some limitations but DDR is not one of them. It will run two sticks of RAM in DDR just fine. You must make sure to mount them in the correct slots on your mobo as instructed in your mobo user's manual.

    DDR simply means that when the memory controller has two sticks of matching Ram to address it will do so twice in a clock cycle. Picture it as reading from one stick while writing to the other (this isn't exactly correct but close enough for our purposes) which in effect doubles your RAM speeds. It does this using both sides of the cpu cycle as voltage rises and then descends.

    Bottom-line is your CPU has this capability and as long as the RAM is in the right slots it will activate automatically.
     
  10. fury

    fury TS Rookie Posts: 38

    Lower latency does give noticeable performance improvements even when you cannot run in dual channel mode.

    Your motherboard supports 184-pin DDR up to PC3200 as indicated by this page and this page

    So basically, look for something that says CL2 (not 2.5), DDR (not DDR2), PC3200, 184-pin, and 1024mb (not 2x512, as this is literally two 512mb sticks), and is made by one of the good manufacturers as noted by Vaerilis.
     
  11. Henner

    Henner TS Rookie Topic Starter

    Thanks again guys for your help, and the time it obviously took you to gather and provide links to the additional sites and data..... I really appreciate it !
    It also makes me realize how much of a computer neophyte I really am...... give me an "E" for effort ?

    So I've taken your advice and have ordered a Corsair TWINX2048-3200C2PT which I think fits the criteria you've outlined. Can't wait to see how they work !
     
     
  12. fury

    fury TS Rookie Posts: 38

    Good choice. I have used Corsair sticks in the past and they are great pieces of memory.
     
  13. Merc14

    Merc14 TS Rookie Posts: 464

    Henner-
    I run the same exact RAM in my A8N SLI Deluxe rig w/ a 3500+ Newcastle. I run these timings for everything but BF2: 2/3/3/6 1T. For BF2 I need to run 2.5/3/3/6 1T or it crashes. Benchmarks games everything but BF2 runs at the former speeds. Except for benchmarking there is no perceptible change in performance between the 2. As for the RAM itself it is rock solid, runs fast and guaranteed for life. Great choice.
     
  14. jayesh

    jayesh TS Rookie

    considering all the rams mentioned i akso just assembled a 3400 a64 on asus a8n-e .... with twinmos ram ...

    seems to be pretty reliable till now
     
  15. Henner

    Henner TS Rookie Topic Starter

    Thanks for your votes of confidence on the module selection.
    FedEx really on the ball. I installed the sticks this afternoon...the system fired right up, and I didn't even need to inject starter fluid in the carburetors ! Jus' kiddin'.

    In the past I couldn't do more than one thing at a time without having the system lock up. Just for grins, I tried to overload it by simultaneously running my Flight Simulator, burning a CD, reading animated email with MSN, and surfing the web with Firefox, and the engine hasn't pinged once. Must be the high octane !

    Have also installed CPU_Z which says the latency is running at 3 3 3 8, instead of the 2.5 3 3 6 which I expected to see after Fury suggested lower latency would perform better.

    Or do I need to somehow adjust the latency manually or otherwise ? I suspect its possible based on Merc14's last memo ?

    Don't fail me now guys.....I just broke the piggy bank to buy these technical wonders.
     
  16. Merc14

    Merc14 TS Rookie Posts: 464

    Henner-
    The following are the settings for a A8N SLI Deluxe Asus mobo:
    Reboot and go into BIOS. Under CPU (I think) is DRAM. Eneter DRAM select manual for settings. RAM settings page opens up.
    Settings:
    memclock or freq - 400.
    CAS Latency (Tcl) - 2 or 2.5 (2.5 works use it first till you gain confidence)
    Ras Activation (Tras) - 6
    Ras to CAS (Trcd) - 3
    Row precharge (Trp) 3
    The above are the biggies, leave the rest as set in BIOS for now. The above is the 2.5/3/3/6 I was talking about.
    Then:
    Timing 1T or 2T set as 1T (this is a big setting. 2T will kill performance)

    Hope it helps. Disable the RAM over 4G setting if you have it.
     
  17. Henner

    Henner TS Rookie Topic Starter

    Merc14,
    Went into the BIOS setup utilities and the CPU Type, Speed, and Cache size are all grayed out with no way to enter or change. All other items deal with adapters, etc that can either be enabled or disabled.

    My Asus K8S-LA motherboard is different than yours, and perhaps its impossible for me to change any Bios settings ?
    Maybe thats just the nature of the beast ?
    Henner
     
  18. fury

    fury TS Rookie Posts: 38

    Your motherboard is indeed different, it is apparently only available to OEMs like HP and Compaq to use to build computers.

    I would suggest contacting HP support and asking them if it's possible to change the memory timings on your board. It may require a BIOS update, using a certain key combination to show hidden settings, or changing jumpers on the motherboard. I am not certain; the HP website for this computer does not appear to be useful enough for me to make any other suggestions.

    Have you used other benchmarking tools as well, to ensure that it didn't simply read the wrong value for the memory timings?
     
  19. Henner

    Henner TS Rookie Topic Starter

    Fury,
    I took an extensive look at the Hp link you provided and couldn't see anything that would help me to adjust the BIOS. I tried calling them, but gave up after waiting an eternity with no response. But I'll keep trying.

    The CPU_Z program was found by accident, and I'm not aware of any other Benchmark programs I could use to confirm or deny what's happening.

    I'm sure you all are getting tired of hearing from me so let me close with a sincere "Thanks very much"

    If you are in the neighborhood of Three Mile Island, look me up....my treat for lunch or dinner.
     
  20. austin_tech

    austin_tech TS Rookie

    Dual channel works with 4 slots?

    Hi Guys,

    sorry for the newbie question...

    I just got my first AMD Athlon system.. a Gateway 5032 with an Athlon 64 x2 4200 CPU.

    When booting up it lists the following specs CL3 DDR400 PC3200 Dual Channel RAM.
    (It has 2 512meg sticks in it.)

    My question : does the Dual Channel technology work across 2 memory banks? (not sure if I worded it right.) i.e. - if I added 2 more 512meg CL3 DDR400 sticks, would the system be able to use all 4 ram sticks together? ...or do I just need to make sure to put 2 of the same memory sticks in the remaining 2 memory slots? (whether they be 256, 512, or 1 gig each)

    Thanks.
     
  21. Merc14

    Merc14 TS Rookie Posts: 464

    Austin tech-
    That is a complicated question but I'll try and give a very simple explanation. DDR is a function of the memory controller. You aren't actually getting 400Mhz speed. The controller basicaly is reading from one stick of RAM at 200MHZ while writing to the other stick at 200MHZ during a single clock cycle, giving you a theoretical RAM read/write speed of 400MHZ. OK, this isn't exactly correct and it rarely works at that speed but you get the picture. Obviously you need two sticks of RAM to get DDR. To get the best performance you need the RAM to be matched.

    Now let's talk about AMD 64 CPU's and chipsets vs. Intel CPU's and chipsets. Intel performs RAM access through the northbridge chipset memory controller or your Front Side Bus (FSB). AGP and/or PCie go through here too. AMD did away with this by placing the memory controller directly on the CPU itself. It accesses the RAM directly via a Hyper Transport Tunnel with huge "bandwidth". There is no FSB. The Northbridge chipset only handles the video or PCIe slots. They still refer to it as FSB because that is the basic measure but there is no FSB on an AMD 64 mobo. This is also why AMD has 1GHZ "FSB" while Intel is just getting around to it.

    The problem with AMD's design is that it is a huge design effort (and expense) to change that on-die memory controller and AMD 64 CPU's have a problem addressing more than two sticks of dual sided RAM (512MB and above are normally dual sided) at full speed. In the older CPU's you were dropped to 333DDR and 2T timing. Your CPU has improved to the point that you can address 4 sticks of dual sided RAM at 400DDR but still at 2T timing (although some are reporting stable 1T timings). This is a performance hit but not as bad as it used to be.

    So, with your newer model CPU the answer is to your question is YES, you can run dual channel across 4 sticks of dual sided RAM and run it at 400DDR speeds but you'll be stuck at 2T timing. Does that matter? Well it depends on your usage.

    If you're a gamer, stick with only two sticks of RAM DDR400 1T timing. Games just like that speedier setting and your performance will be better. They'll run OK at 400DDR 2T and you'll probably see the performance hit in benchmarks only so you're call. If you're video editing then 400DDR at 2T timing isn't a big deal and I'd suggest that you load that puppy up with as much RAM as you can afford.
     
  22. Henner

    Henner TS Rookie Topic Starter

    Austin,
    I'm not qualified to answer your question, as I posted the orginal thread, but If you read through the replies you will note that the AMD in my Compaq will not run in dual channel mode as it has a socket 734, instead of the required 939 to make it happen.

    Since you have a Gateway with 2 slots of 512 in dual channel mode, I would conclude that your system will continue to run in dual channel if you added two more sticks of like kind and type. If you mix size and type, I remember reading that you must be careful to match slots like 1 to 3, 2 to 4 , etc.

    Hopefully one of the knowledgeable guys like those that helped me will come to your rescue.
     
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