how-to block ads
said by Anandtech:
Take note that the memory isn't dual channel, the platform is. In fact there is no such thing as dual channel memory. Rather, it is a memory interface composed of two (or more) normal memory modules coordinated by the chipset on the motherboard, or in the case of the Athlon64 FX and Opteron processors, coordinated by the integrated memory controller. But for the sake of simplicity, we refer to DDR dual channel architecture as dual channel memory.
The nforce2 platform has two 64bit memory controllers (which are independent of each other) instead of just a single controller like other chipsets. These two controllers are able to access "two channels" of memory simultaneously. The two channels, together, handle memory operations more efficiently than one module by utilizing the bandwidth of two modules (or more) combined. By combining DDR400 (PC3200) with dual memory controllers, the nForce2 could offer up to 6.4GB/sec of bandwidth in theory. It is also possible for DDR Dual Channel architecture to reduce system latencies and timing delays that inherently occur with one memory module. For example, one controller reads and writes data while the second controller prepares for the next access, hence, eliminating the reset and setup delays that occur before one memory module can begin the read/write process all over again. Think of it like two relay runners. The first runner runs one leg while the second runner sets up and prepares to receive the baton smoothly and carry on the task at hand without delay.
However, this extra bandwidth produced by dual channel cannot be fully utilized by the Athlon XP and Duron family (K7) of processors. The system bus on an Athlon XP doesn'tt know the difference between Dual Channel and a TV Channel. Data(bandwidth) will reach these processors no sooner than the system bus (FSB) allows them, and the processor therefore largely cannot derive an advantage from memory operating faster than DDR266 when operating on a 133/266Mhz FSB, DDR333 with a 166/333Mhz FSB or DDR400 at 200/400Mhz FSB even in single channel mode. Visualize a four lane highway, symbolizing your Dual Channel configuration. As you go along the highway you come up to a bridge that is only 2 lanes wide. That bridge is the restriction posed by the dual-pumped AMD FSB. Only two lanes of traffic may pass through the bridge at any one time. That's the way it is, with the K7 processors and Dual Channel chipsets. In case you're wondering, the K in K7 stands for Kryptonite, later changed to Krypton to avoid copyright infringement. Yes, that very same fictional element from comic books that could bring the otherwise all-powerful Superman (Intel ) to his knees. Cool eh? how K endured in the names of various AMD chips for several years and even in the ones to come.
Intel's P4 architecture, in contrast, is designed to exploit the increased bandwidth afforded by dual channel memory architectures. The quad pumped P4 FSB seemed like drastic overkill in the days of single channel SDR memory, but is paying handsome dividends in today's climate of dual channel DDR memory subsystems. This is one lasting and productive legacy of Intel's RDRAM efforts. As implemented on the P4 RDRAM was also dual channel architecture, and mandated the quad-pumped FSB for its extra bandwidth to be exploited. This factor continues to serve the P4 well in the dual channel DDR era we are currently in, and allows P4's greater memory performance than all other PC platforms, save the new AMD Athlon 64 FX with all its new bells and whistles.
The Athlon 64 FX processor has a fully integrated DDR Dual Channel memory controller providing a 128-bit wide path to memory and therefore eliminating the need for a Dual Channel interface on the motherboard which traditionally was always located in the northbridge. Although the P4 (800fsb variety) and the A64 FX, both share the same theoretical peak memory bandwidth of 6.4GB/sec, the Athlon FX realizes significantly more throughput due mainly to its integrated memory controller. Even so, it still suffers from the required use of registered modules which are slower than regular modules, in terms of subsystem latency. The upcoming Athlon 64 / A64 FX processors designed for Socket 939 will be free from this major drawback and will also feature Dual Channel memory controllers.
Interesting graphic (video type) presentation basic lessons on memory and how it works. Also defines the terms and timing values we see discussed so frequently on this forum. You can skip the last 6 slides or so unless you want to hear the Corsair marketing.
Actual clock speed/effective transfer rate
100/200MHz => DDR200 or PC1600 DDR
133/266MHz => DDR266 or PC2100 DDR
166/333MHz => DDR333 or PC2700 DDR
185/370MHz => DDR370 or PC3000 DDR
200/400MHz => DDR400 or PC3200 DDR
217/433MHz => DDR433 or PC3500 DDR
233/466MHz => DDR466 or PC3700 DDR
250/500MHz => DDR500 or PC4000 DDR
267/533MHz => DDR533 or PC4200 DDR
283/566MHz => DDR566 or PC4500 DDR
In a word, Yes.
But it doesn't always work and so, it is generally preferable to avoid doing this. The risks of running into problems are greatly increased if the modules used have different arrangement, size and SPD programming. A system will only run at speed of the slowest module, if you mix different speed modules. As you will see, some systems automatically detect the properties of memory modules being used, and set the system timing accordingly. They usually only look at the speed of the memory in the first bank when setting this timing. So if you use two or more dissimilar modules, it is advisable to place to the slowest module in the first slot. If the system doesn't't have this 'auto-detection' or you've disabled the 'auto-detection', it won't be much of an issue, but it's still good practice.
As well, if the goal is overclocking, often the best results are obtained with perfectly matched modules. Additionally dual channel architectures generally work very poorly with mis-matched modules. There is no guarantee a mismatch won't work for one reason or another, and it won't really hurt anything to try (assuming your data is backed up), but to maximize the chances of success modules should match.
Q: Which slots to use?
If you're using a single module, it's best practice to use the first slot. Q: I've had my single module installed in slot 2 for the last few months now, should I change it? No, it's also best practice to keep on using the slot(s) you're been using before. If you replace RAM, then insert the new modules, in the same slots the older ones were in before.
You may find the system overclocks better with the ram in a different slot. It is very hard to predict when this effect occurs, as well as which one might work best. In the overclocking game he who tries the most things wins, and if you are running an overclocked configuration that is asking a lot of the ram it is a good idea to try all available slots to make sure the one you are using yields the best results.
If using two or more modules in a non-dual channel motherboard, populate the first slot and use any other slots you wish.
If you're using two or more modules of unequal size, you will get the best performance if you put the largest module(s) (in megabytes) in the lowest-numbered slot(s). For example, if your system currently has 256MB of memory and you want to add 512MB, it would be best to put the 512MB module into slot 0 and the 256MB module into slot 1.
Most dual channel capable nforce2 motherboards come with three slots. On these motherboards the first memory controller controls only the first slot (or the slot by itself), while the second memory controller controls the last two slots (which are usually closer together). Name them slots 1, 2 & 3 respectively. To implement Dual Channel, it is necessary to occupy the slot 1 (channel 0) and either one of the two slots that are closer together, slots 2 or 3 (channel 1) The entire config would be running in 128bit mode.
You can use three modules in Dual Channel Mode, by filling the third unoccupied slot. With three sticks, slots 1 remains as channel 0 while slot 2&3 become channel 1. To maintain 128-bit mode, with all three slots filled, each channel must have an equal amount of memory. For example, slots 1 should be filled with a 512Mb module, while slots 2 & 3 are populated 256Mb modules. If you were to use three modules of the same size, then only first two modules would be running in 128bit Dual Channel Mode. Example, using 3x 256Mb modules will have the first 512Mb running in 128bit Dual Channel mode, while the remaining 256Mb will be in 64-bit Single Channel mode.
Intel dual-channel systems are different. The have either two or four slots, and to run dual channel mode must have either one or two pairs of (hopefully) matching modules. Running three modules on a P4 system will force it to run in single channel mode, and is therefore to be avoided.
Consult your motherboard manual for instruction on exactly which slots exactly to use.
Memory performance is not entirely determined by bandwidth, but also the speeds at which it responds to a command or the times it must wait before it can start or finish the processes of reading or writing data. These are memory latencies or reaction times (timings). Memory timings control the way your memory is accessed and can be either a contributing factor to better or worse 'real-world' performance of your system.
Two basic signals are sent to the RAM in order for it to read/write data, address and control. The address is of course where the data is located on the memory banks, and the control signals are various commands needed to read or write. There is a delay before a control signal can be executed or finish and this is where we get latencies. The standard format for memory latencies are most often expressed as a string of four numbers, separated by dashes, from left to right or vice-versa like this 2-2-2-6 [CAS-tRP-tRCD-tRAS] . These values represent how many clock cycles long each delay is but are not expressed in the order in which they occur. Different bioses will display them differently and there maybe additional options (timings) available.
Command rate - is the delay (in clock cycles) between when chip select is asserted (ie. the RAM is selected) and commands (i.e. Activate Row) can be issued to the RAM. Typical values are 1T (one clock cycle) and 2T (two clock cycles). Mushkin has a good write up about CMD rate here
CAS (Column Address Strobe or Column Address Select) - is the number of clock cycles (or Ticks, denoted with T) between the issuance of the READ command and when the data arrives at the data bus. Memory can be visualized as a table of cell locations and the CAS delay is invoked every time the column changes, which is more often than row changing.
Trp (RAS Precharge Delay) - is the speed or length of time that it takes DRAM to terminate one row access and start another. In simpler terms, it means switching memory banks.
Trcd (RAS (Row Access Strobe) to CAS delay) - As it says it's the time between RAS and CAS access, ie. the delay between when a memory bank is activated to when a read/write command is sent to that bank. Picture an Excel spreadsheet with a number across the top and along the left side. They numbers down the left side represent the Rows and the numbers across the top represent the Columns. The time it would take you, for example, to move down to Row 20 and across to Column 20 is RAS to CAS.
Tras (Active to Precharge or Active Precharge Delay) - controls the length of the delay between the activation and precharge commands ---- basically how long after activation can the access cycle be started again. This influences row activation time which is taken into account when memory has hit the last column in a specific row, or when an entirely different memory location is requested.
tRC (Row Cycle) & tRFC (Row Refresh Cycle) - tRC is the minimum time interval between successive active commands to the same bank.
These timings or delays occur in a particular order. When a Row of memory is activated to be read, there is a delay before the data on that Row is ready to be accessed, this is known as tRCD (RAS to CAS, or Row Address Strobe to Column Access Strobe delay). After the Row has been activated, the read command is sent, and the delay before it starts actually reading is the CAS (Column Access Strobe) latency. When reading is complete, the Row of data must be de-activated, which requires another delay, known as tRP (RAS Precharge), before another Row can be activated. The final value is tRAS, which is the minimum Active to Precharge delay. Once a row is activated, it cannot be de-activated until the delay of tRAS is over.
TCCD refers to Samsung tccd IC's used on the ram. They overclock real well at lower latencies.
Ram with Samsung TCCD
Confirmed Samsung TCCD
Adata PC4500 Vitesta
Adata PC4800 Vitesta
Centon Advanced DDR
Corsair XMS PC3200C2 Rev4.1 2-3-3-6-1T
Geil UltraX pc3200 ~ Brainpower PCB
Gskill PC4400 (various) ~ Brainpower PCB ~ Not in UK (15/10/04)
Kingston HyperX PC 3200ULK2 ~ Not in UK (15/10/04)
Mushkin PC3200 Rev.2
OCZ PC3200 Rev.2 ~ Brainpower PCB
OCZ PC3700 Platinum
Patriot Extreme Performance PDC5123200+XBLK ~ Brainpower PCB
PQI 3200 Turbo 2-2-2-5 ~ Brainpower PCB
Samsung PC4000 CL3 ~ Not in UK (15/10/04)
Twinmos Twister Pro (ALL BRANDS?)
Possible Samsung TCCD
Corsair XMS PC3200C2 Rev4.2 2-3-3-6-1T
Samsung OEM PC3200
Confirmed Samsung TCCC Memory
Corsair XMSPC3700 Rev1.1
Possible Samsung TCCC Memory
Adata PC4000 (can be Hynix D43, D5)
Kingston HyperX PC4000/K2 (can be Hynix D43, D5)
Kingston Value Ram PC3200 (can be D43, D5, Samsung TCCC, TCC4)
Samsung Original PC3200 (can be TCC4)
In order to really maximize performance from your memory, you'll need to gain access to your system's bios. There is usually a Master Memory setting, often rightly called Memory Timing or Interface, which gives usually gives you the choice to set your memory timings by SPD or Auto, preset Optimal or Aggressive timings (e.g. turbo or ultra), and lastly an Expert or Manual setting that will enable you to manipulate individual memory timing settings to your liking.
Are the gains of the perfect, hand-tweaked memory timing settings worth it over the automatic settings? If you're just looking to run at stock speeds and want absolute stability, then the answer to that question would probably be no. You're better off going by SPD or Auto. You generally do not have a choice if you overclock or want to tweak more performance out of your system.
Q: Ok so I want to tweak, What do I do?
When tweaking your memory, the first step is to deactivate the automatic RAM configuration ---- SPD or Auto. When this function is activated, the motherboard reads the SPD chip (explained in next topic) on the memory module to obtain information about the timings and clock speed and to adjust the settings accordingly. However, these settings, which the RAM manufacturer stores in this chip, are very conservative in order to ensure stable operation on as many systems as possible. With a manual configuration, you can customize your settings for your own system - in most cases, the RAM modules will remain stable even when they exceed the manufacturer's specifications.
As a general rule, a lower number (or timing) will result in improved performance. After all, if it takes fewer cycles to complete an operation, then it can fit more operations within X amount of time. You might ask: Why can't we use 1 or even 0 values for memory timings? Good Question. There's a good answer. JEDEC specifies that it's not possible for current DRAM technology to operate as it should under such conditions. Depending on motherboard, you might be able to squeeze '1' on certain timings, but will very likely result memory errors and instability. And even if it doesn't't, it is unlikely to result in a performance gain.
If you are not planning on overclocking the clock speed of your RAM or if you have fast RAM rated at speeds above that of your current FSB, it may be possible to just lower the latencies for a nice performance gain. Memory Latencies can vary depending on the performance of RAM chips used. Not all memory modules will exhibit the ability to use certain latencies without producing errors. So testing, trial and error, is required.
Here are general guidelines to follow while "tweaking":
lower figures = better performance, but lower overclockability and possibly diminished stability.
higher figures = lesser performance, but increased overclockability and more stability -- to an extent
tRCD & tRP are usually equal numbers between 2 and 4. In tweaking for more overclockability, lower tRCD first between these two
CAS is not most critical of the various timings, unlike what is taught by many.
In general, the importance of CAS when placed against tRP and tRCD is nominal. Reducing CAS has a relatively minor effect on memory performance, while lower tRP & tRCD values result in a much more substantial gain. In other words if you had to choose, 3-3-2.5 would be better than 4-4-2.0 (tRCD-tRP-CAS)
CAS should be either 2.0 or 2.5. Many systems, most nforce2, fail to boot with a 3.0 setting or have stability problems.
tRAS should always be no less than the sum of CAS & tRCD see below
tRC is usually no less than the sum of tRAS and tRP. So if you have a tRAS of 11 and tRP of 2....then tRC should be 13. tRFC should be tRC + 2.
tRAS is unique, in that lowering it can lead to problems and lesser performance. tRAS is the only timing that has NO effect on real performance, if it is configured as it should. Sure a high tRAS on the nForce2 chipsets shows a better sandra score. But real-life performance is the same with different tRAS settings as long as tRAS is no less than the sum of tRCD and CAS Latency. Lower than this sum, can and will negatively affect your system's performance.
This document from Mushkin outlines how tRAS should be a sum of tRCD, CAS, and 2. For example, if you are using a tRCD of 2, and a CAS of 2 on your RAM, then you should set tRAS to 6. At values lower than that theory would dictate catastrophic consequences for data integrity including Hard drive addressing schemes --- truncation, data corruption, etc --- as a cycle or process would be ended before it's done. How is it possible for memory timings to affect my hard drive? When the system is shut down or a program is closed, physical ram data that becomes corrupted may be written back to the hard drive and thats where the consequences for the hard drive come in. Also lets not forget when physical ram data is translated by the operating system to virtual memory space located on the hard drive.
While it's important to consider the advice of experts like Mushkin, your own testing is still valuable. Systems both AMD & Intel can indeed operate with stability with 2-2-2-5 timings, and even exhibit a performance gain as compared to the theoretically mandated 2-2-2-6 configuration. The most important thing in any endeavor is to keep an open mind, and don't spare the effort. Once you've tried both approaches extensively it will be clear to you which is superior for your particular combination of components.
The memory speed should always be dependant on the speed of the front side bus (FSB). When memory runs at the same speed as the FSB, it is said to be running in synchronous operation. When memory and FSB are clocked differently (lower or higher than), it is known as asynchronous mode.
Only Intel chipsets have implemented async modes that have any merit. If you are talking about the older i845 series of chipsets, running an async mode that runs the memory faster than the FSB is crucial to top system performance. And with the newer dual channel Intel chipset (i865/875 series) in an overclocked configuration, often you must run an async mode that runs the memory slower than the fsb for optimal results. The async modes in SiS P4 chipsets also work correctly.
When looking at the AMD-supporting chipsets async mode are to be avoided at all costs. AMD-supporting chipsets offer less flexibility in this regard due to poorly implemented async modes. Even if it means running our memory clock speed well below the maximum feasible for a given memory, an Athlon XP system will exhibit best performance running the memory in sync with the FSB.
To achieve synchronous operation, there is usually a Memory Frequency or DRAM ratio setting in the bios of your system that will allow you to manipulate the memory speed to a either a percentage of the FSB (ie. 100%) or a fraction (or ratio) ie. N/N where N is any integer available to you. Here are some examples:
200MHz FSB speed with 100% or 1:1 (FSB:Memory ratio) results in 200MHz memory speed (DDR400)
200MHz FSB speed with 120% or 5:6 (FSB:Memory ratio) results in 240MHz memory speed (DDR480)
250MHz FSB speed with 80% or 5:4 (FSB:Memory ratio) results in 200MHz memory speed (DDR400)
The first example is wholly acceptable for any AMD system, memory should be set this way at all times for best performance. Asynchronous FSB/Memory Speeds are horridly inefficient on AMD systems, but may well be the optimal configuration for P4 systems.
The second example shows running the Memory at higher asynchronous speeds. Assume we have a Barton 2500+ which has a FSB of 333 MHz (166 MHz X 2) and we also have PC3200 memory running at 400 MHz (PC3200). This is a typical scenario because many people think that faster memory running at 400 MHz will speed up their system. Or they fail to disable the SPD or Auto setting in their bios. There is NO benefit at all derived from running your memory at a higher frequency (Mhz) than your FSB on Athlon XP/Duron systems. In actuality, doing so has a negative effect.
Why does this happen? It happens because the memory and FSB can't "talk" at the same speeds, even though the memory is running at higher speeds than the FSB. The memory would have to "wait for the FSB to catch up", because higher async speeds forces de-synchronization of the memory and FSB frequencies and therefore increases the initial access latency on the memory path ---- causing about a 2 - 5% degradation in performance.
This is another ramification of the limiting effect of the AMD dual-pumped FSB. A P4's quad pumped FSB (along with the superior optimization of the async modes) allows P4's to benefit in some cases from async modes that run the memory faster than the FSB. This is especially true of single channel P4 systems. There still are syncronizaton losses inherent in an async mode on any system, but the adequate FSB bandwidth of the P4 allows the additional memory bandwidth produced by async operation to overcome these losses and produce a net gain.
The third example is most often used in situations where the memory is not able to keep up with the speed of the FSB. In such a situation, your best option, if using an AMD system, is to lower the FSB to a point where it is synchronous with the memory speed and increase the multiplier (CPU ratio) instead. It is also a common scenario, where a user has PC2100 (266Mhz) memory and tries to pair it with a 333Mhz FSB processor. While some PC2100 memory are capable of PC2700 and higher, many others may not overclock as well. The only real benefit on async modes on AMD system is the fact it comes in handy to overclockers for testing purposes; to determine their max FSB and to eliminate the memory as a possible cause for not being able to achieve a desired stable FSB speed.
Looking to the Intel side of the fence, async modes that run the memory slower than the FSB have merit because of how async modes are implemented in the Intel chipsets. This is extremely important, as we cannot change the CPU multiplier on modern Intel systems and therefore have to use and async mode to allow substantial overclocks on the majority of systems utilizing the current 200/800MHz fsb family of P4 processors.
Feedback received on this FAQ entry:
The front side bus is what connects the processor to the rest of the system. To improve performance, you increase the frequency therefore shortening the time it takes to transfer data. Improving overall system performance is the process of removing bottlenecks and making paths that aren't already bottlenecked as fast as possible. Since FSB frequency and Memory frequency are most times made to be the same, this poses a problem - as overclockers look for the highest possible FSB while the memory may struggle behind at a slow speed. Many boards (usually older ones) will run the memory bus at the same speed as the FSB and there is no way of changing it. Most newer boards allow you to alter the speed of the memory bus in relation to the FSB.
There is really no point having a high FSB, if the memory cant keep up. When the memory or any other component is holding back system performance, this is called a bottleneck. An example of a memory bottleneck would be if you were running your memory at DDR 333 MHz with a 400 MHz system bus. The memory would only be providing 2.7GB/s of bandwidth while the bus would be capable of transmitting 3.2GB/s of bandwidth. A situation like this would not help overall system performance.
Think of it like this; let's say you had a highway going straight into a mall, with an identical highway going straight out of the mall. Both highways have the same number of lanes and initially they have the same 45mph speed limit. Now let's say that there's a great deal of traffic flowing in and out of the mall and in order to get more people in and out of the mall quicker, the department of transportation agrees to increase the speed limit of the highway going into the mall from 45mph to 70mph; the speed limit of the highway leaving the mall is still stuck at 45mph. While more people will be able to reach the mall quicker, there will still be a bottleneck in the parking area leaving the mall - since the increased numbers of people that are able to get to the mall still have to leave at the same rate. This is equivalent to increasing the FSB frequency but leaving the memory frequency/bandwidth unchanged or set to a slower speed. You're speeding up one part of the equation while leaving the other part untouched.
Sometimes the fastest memory is not always afforded or available. In this case, more focus should be placed on balancing the FSB and memory bandwidth while still keeping latencies as low as possible AND while still maintaining CPU clock speed (GHz). The benefit of a faster FSB (and higher bandwidth) will only become more and clearer as clock speeds (GHz) increase; the faster the CPU gets, the more it will depend on getting more data quicker.
The memory timings can also play a role in how far the memory will go, in keeping with the FSB. Lower timings (numbers) will hinder how fast the memory can run, while higher timings allow for more memory speed.
Feedback received on this FAQ entry:
You can find them Here or Here where you can get some more information on them.
Feedback received on this FAQ entry:
Although the Vdimm has nothing to do with the CPU itself, it plays an integral part in the big picture. If we are running a synchronous mode (1:1), the CPU's FSB and RAM MHz go up at a 1:1 ratio. For every 1MHz increase in FSB speed, the RAM speed will increase by 1MHz. So in these cases an elevated memory voltage will often prove helpful in maximizing the overclocking potential of the CPU.
A few points to consider when raising memory voltage:
Like CPU overclocking, increasing memory voltage should be done in the smallest increments available.
0.3 Volts over Default - That's a bit conservative for some people (including me), but should be enough for most. This is also the maximum provided by most motherboards. On such motherboards, hardware mods or modified bioses maybe required to gain access to more voltage.
Some of the higher voltages (2.9v to 3.3v) available on certain motherboards may damage the RAM with long exposure, so check with other people who have your RAM to get a feel for its voltage tolerance. The memory you save may be your own.
Take a look at the markings on the chips of your memory. Each chip is covered with numbers and those numbers have tell what chips they are and may even have the logo and name of the chip maker. If your memory has heatspreaders, it will have to be carefully removed to see the memory chips.
Why does this matter? Well like motherboards, for example, not all brands offer the same performance and overclocking potential. The same goes for memory chips. So people (usually overclockers) seek out certain preferred brands of memory chips for their systems. Check your manufacturers website, they may or may not list what chips they use their modules.
Well, like most other PC components, all RAM are not created equal. For DDR400, you can find memory varying from - very fast modules supporting 2-2-2-5 timings (CAS-tRP-tRCD-tRAS) from Mushkin, Corsair, OCZ (for example), to relatively low-cost modules that aren't as favorable with the timings. Many DDR400 modules currently available require the use of CAS Latency = 2.5, but this is not the worst variant. Note that the CAS Latency parameter alone does not influence the memory subsystem speed too much. Two other parameters, namely tRP and tRCD, affect the results much more heavily. This is a curious fact, considering that many memory sellers usually draw the customers attention to the CAS Latency parameter, often without even mentioning the other ones. So, it's recommended that you note that modules with CL = 2.5 or 3 will not in all probability work with minimal trp & trcd settings.
Q: What Memory to buy?
Touchy subject for some. For others, RAM is RAM, right? Riiiiight!!!!
If you plan on overclocking, I can't stress this enough - YOU NEED HIGH QUALITY COMPONENTS!! I can't tell you how many times I've tried to help people out with overclocking their systems and come find out that the one problem was they have no-name PC2100 dimms stuffed in their slots. Ick. One thing I can say with certainty is that you should buy PC3200 at the minimum for any new system - AMD or Intel. Not only for overclocked systems but for the sake of performance in general. Depending on the brand there isn't really much of a price differential between quality PC2700 and PC3200, so get PC3200. Quality RAM is not always expensive, but expensive RAM is often quality.
However, buying much faster RAM, isn't always the best idea, especially for AMD chipsets. Overall, PC4000 and higher modules are not quite compatible with these motherboards. It is advisable to stick with lower latency PC3200 or PC3500 modules. Just above every PC3700+ memory have high latency timings. Consider that Fighter Jet A is your PC4000 memory and is built for super-fast speeds, but cannot maneuver as well as Fighter Jet B which is lower latency PC3200. In a dog fight on AMD terrain, Fighter Jet B will win because the terrain is mountainous and requires more maneuverability. Likewise, Fighter Jet A would have more of a chance in Intel terrain because on such a terrain speed matters more and maneuverability (or latency) isn't as important. But since, as discussed earlier, we can realistically use an async mode on Intel systems, it may well prove that doing so and using top quality PC3200 or PC3500 memory and their attendant lower latency will allow Fighter Jet B to triumph in most all cases.
Bottom line is, don't skimp on your RAM selection. You'll be kicking yourself later if you do. But just the same, don't assume that because a particular memory type is expensive it is also superior for your application.
More memory will not increase the speed of the CPU, but it will reduce the time a CPU spends waiting for information from a hard drive. The operating system and applications will be able to load more of their data into ram at once, and the dependence on virtual memory will be reduced. Since RAM provides data to a CPU faster than a hard drive, you will not have to wait as long for programs to execute in most cases. If you want your computer to run faster in nearly all cases, consider upgrading the CPU or overclocking.
Feedback received on this FAQ entry:
Companies like Corsair, Mushkin, OCZ, etc produce what they call "dual channel" memory, or Dual Channel Kits. These are sold in pairs, so for instance you might buy a 512MB or 2x256MB Dual Channel Kit, which consists of 2 sticks of 256MB DDR memory paired together by the manufacturer.
Companies don't just throw two sticks of RAM together to produce these kits, but they don't necessarily produce a totally different batch of RAM either. Testing or qualifying Dual Channel memory might involve something as simple as technicians booting up pairs of RAM in a Dual Channel motherboard and ensuring they work together under a set of conditions, or it could be more complicated, including so called "SPD" optimisation's and even chip selection (we're inclined not to put much trust in any of those claims ). For your purposes, you should assume that Dual Channel memory is qualified through testing as all companies will claim that every pair of Dual Channel memory is tested prior to being packaged.
Q: Will Non-Dual Channel Matched RAM work in my nforce2 motherboard?
It most certainly, will. As long as it fits the requirements of Dual Channel operation (two of the same types of memory, same size modules, speed, etc). Two modules of the same model/brand purchased from the same vendor at the same time is essentially as likely to work properly in a dual channel configuration as is a dual channel kit.
The ONLY thing you can lose by buying "single channel" memory for use in Dual Channel mode is that manufacturers may or may not provide support and replace your memory if it won't work in dual channel mode, whereas if Dual Channel memory fails to work in Dual Channel mode, the manufacturers will help you resolve the problem and possibly replace the memory to ensure proper Dual Channel operation.
There are instances of people using two different types of RAM together and have had no problems. You can't damage your motherboard or RAM just by trying to use two un-identical module in Dual Channel mode. But be advised that if the machine is unstable for any reason, it is entirely possible to corrupt your data upon operation of the machine. Mis-matched memory sticks in a dual channel configuration often produce unstable operation, so as with any new overclocking or upgrading venture make sure you have adequate backups so you can recover from a data loss.
Note:If overclocking with FSB (usually when at very high FSB speed), setting your memory to have very low latency can cause instability to the whole system.
Also see this post by C0deZer0.
Memory timings vs. Bandwidth
xbitlabs article on choosing memory for P4 systems
Corsairs Memory basics guide (flash)
How to use Memtest 86 for memory burnin
THG Memory Timings Put to the Test
Please remember that higher speed memory runs with looser timings that LL (low latency) RAM. Memory that is rated at DDR500+ runs looser timings than memory rated for speeds of under DDR500. If you are not going to run DDR500+ speeds you should consider buying ram with lower latencies like DDR400-433 memory.
If you want to know »Overclocking »Why are memory timings important? then read this FAQ entry.
The first and most popular is Memtest86. You can download it as a bootable CD image or flopy image
The alternative to memtest86 is the Microsoft Memory Diagnostic program.