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Clock Killer
Senior Member
Posts: 644
Last Seen: 10-29-2009
From: Ga
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Memory: Ultimate RAM guide
Ultimate RAM guide
Im going for sticky quality here but I must say first that I cannot take all the credit for this. Some of this I wrote personally and some is a collaboration of info from other websites. I will site my sources at the bottom of the page. I will also go ahead and state that any knowledge obtained from this post will be yours to interpret and I will hold no responsibility for your actions on how you choose to use this information and I will not be held responsible for any damages that may be brought about by the use of this information.
Okay, where to begin, lets start by talking about the differences between SDRAM, DDR, DDR2, and DDR3.
SDRAM: SDRAM stands for “Synchronous Dynamic Random Access Memory. While good old SDRAM has been out of date for some time, it is still worth mentioning as all current memory standards are based on SDRAM. Typical SDRAM speeds include 66MHz, 100MHz, and 133MHz. JEDEC standard voltage is 3.3V. In the case of SDRAM, the data clock is synchronous to the bus clock. Modules come with 168 pins.
DDR: DDR stands for double data rate. It was one of the first major breakthroughs in RAM technology that allowed for RAM to send and receive data two times per clock cycle, with a data strobe pulse at both the leading edge and falling edge of the clock cycle. With data being transferred 64 bits at a time, DDR SDRAM gives a transfer rate of (memory bus clock rate) × 2 (for dual rate) × 64 (number of bits transferred) / 8 (number of bits/byte). Thus with a bus frequency of 100 MHz, DDR-SDRAM gives a maximum transfer rate of 1600 MB/s. The introduction of the DDR concept has also given users the abilities to work with “half-cycle” timings in terms of latency. Because data is being read out twice for every clock cycle, we can now have latencies set for half-clock cycles instead of whole cycles, giving the user additional flexibility. DDR DIMMS have 184 pins as apposed to the 168 pins on SDRAM DIMMS and 240 pins on DDR2 and DDR3 DIMMS. Standard JEDEC speeds are DDR-200, DDR-266, DDR-333 and DDR-400, with the actual bus clock being half of those speeds. JEDEC standard voltage is 2.5V.
DDR2: Since DDR stands for double data rate, by conjecture im sure you know that DDR2 stands for double data rate two. Like DDR before it, DDR2 cells transfer data both on the rising and falling edge of the clock (a technique called "dual pumping"). The key difference between DDR and DDR2 is that in DDR2 the bus is clocked at twice the speed of the memory cells, so four words of data can be transferred per memory cell cycle. Thus, without speeding up the memory cells themselves, DDR2 can effectively operate at twice the bus speed of DDR. This however comes at a cost, the latencies of these chips are greater, usually in the 4 to 6 range. As a side note it important to recognize that DDR2 DIMMs are not designed to be backwards compatible with DDR DIMMs. The notch on DDR2 DIMMs is in a different position than DDR DIMMs, and the pin density is slightly higher than DDR DIMMs in desktops. Another advantage that DDR2 brings to the table is that it is more energy friendly and therefore a more economical and efficient technological development. This is due primarily to die shrinkage. DDR2 also accommodates for newer process technologies that allow higher densities in the same package while also allowing for lower voltage. Standard JEDEC speeds for DDR2 are DDR2-400, DDR2-533, DDR2-800, and DDR2-1066. Standard JEDEC voltage is 1.8V.
DDR3: Once again by conjecture I'm sure that you have realized that DDR3 stands for double data rate three. Its primary benefit is the ability to run its I/O bus at four times the speed of the memory cells it contains, thus enabling faster bus speeds and higher peak throughputs than earlier technologies. This once again comes at a cost of latency. Also, the DDR3 standard allows for chip capacities of 512 mbit to 8 gbit, effectively enabling memory modules of maximum 16 GB in size. DDR3 memory comes with a promise of a power consumption reduction of 30% compared to current commercial DDR2 modules due to DDR3's 1.5 V supply voltage, compared to DDR2's 1.8 V or DDR's 2.5 V. The main benefit of DDR3 comes from the higher bandwidth made possible by DDR3's 8 bit deep prefetch buffer, whereas DDR2's is 4 bits, and DDR's is 2 bits deep. For almost all intents and purposes the DDR3 technological advancement was not nearly as dramatic and ground breaking as the step from DDR to DDR2. Once again, DDR3 is not designed to be backwards compatible with DDR2 because DDR3 DIMMs have 240 pins which happens to be the the same number as DDR2, and are the same size, but are electrically incompatible and have a different key notch location. Some other new things that the DDR3 technology implements are the introduction of asynchronous RESET pin, and On-DIMM Mirror friendly DRAM pin outs. Many memory controllers that support DDR3 support DDR2 as well; so having support for both standards on the same motherboard are not uncommon, however they both require their own dedicated slots. DDR3 also accommodates further advancements in the fab process which allow higher densities at lower voltage. Standard JEDEC speeds for DDR3 are DDR3-800, DDR3-1066, DDR3-1333 and DDR3-1600. Standard JEDEC voltage is 1.5V.
Advantages compared to DDR2- Higher bandwidth performance increase (up to effective 1600 MHz)
- Performance increase at low power (longer battery life in laptops)
- Enhanced low power features
- Improved thermal design (cooler)
Disadvantages compared to DDR2 - Commonly higher CAS Latency
- Generally costs much more than equivalent DDR2 memory.
How data is transferred from memory to CPU :
1) The CPU sends a signal specifying the memory row and bank that it wants to access via the RAS line.
2) After a period of time (RCD) the CPU sends a signal to the CAS line, specifying the column to be accessed.
3) After CAC time period, the data moves to the output line.
4) The CPU expects the data to 'appear' upon a specific clock cycle after sending the request.
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Next on the list will to be to explain the all important RAM timings. RAM timings have the potential to enhance performance of RAM by two or three times but on the contrast scenario have the ability to leave your system in a completely non-functioning state. Read all of this section before you go tweaking away. As a side note that should be mentioned, when you see advertised timings, the 4 that are shown are the ones that hold the only viable performance gains. The other timings could possibly improve memory performance or reliability but these are not very plausible means of improving RAM performance. There is little to no really helpful documentation on those timings anyway. CAS: CAS stands for column address strobe latency referring to the column of the physical memory location in an array (comprised of columns and rows) of capacitors. CAS Latency (CL) is the time (in number of clock cycles) that elapses between the memory controller telling the memory module to access a particular column in the current row, and the data from that column being read from the module's output pins. Most people think that this is the most influential timing that affects RAM performance. This assumption is wrong but not very far off. CAS has a large impact on the performance of RAM but it has been proven that tRP and tRCD produce more of a substantial gain. e.g.: 2.5-3-3-8 The bold “2.5” is the CAS timing.Normal setting per technological implementation: - DDR: common settings are 2, 2.5, and 3.
- DDR2: common settings are 4, 5, and 6.
- DDR3: common settings are 7,8, and 9. (5&6 plausible)
tRCD: tRCD stands for RAS to CAS delay (Row Address Strobe to Column Address Strobe). This is one of the more influential timings. This is the amount of time in cycles for issuing an active command and/or the read/write command. e.g.: 2.5-3-3-8 The bold “3” is the tRCD timing.Normal setting per technological implementation: - DDR: common settings are 2, 3, and 4.
- DDR2: common settings are 3, 4, and 5. (6 plausible)
- DDR3: common settings are 5, 6, 7, 8, and 9.
tRP: tRP stands for row precharge (delay). This again is one of the more influential timings. This basically is the minimum amount of time between active commands and the read/write of the next bank on the memory module. e.g.: 2.5-3-3-8 The bold “3” is the tRP timing.Normal setting per technological implementation:
Command Rate: Also called CPC (Command Per Clock). The amount of time in cycles when the chip select is executed and the commands can be issued. The lower (1T) the faster the performance, but 2T is used to maintain system stability. On Intel based machines, 1T is always used where the number of banks per channel are limited to 4. Most intel based motherboards don't cooperate well with 1t command rates even if the memory module is able to support it. Most times it will produce memory corruptions (especially with overclocking) which results in very poor performance.
(the following timings in my opinion have yeilded little to no performance gains as to the default (auto) setting.)
tRC Timing: Row Cycle Time. The minimum time in cycles it takes a row to complete a full cycle. This can be determined by; tRC = tRAS + tRP. If this is set too short it can cause corruption of data and if it is to high, it will cause a loss in performance, but increase stability.
tRRD Timing: Row to Row Delay or RAS to RAS Delay. The amount of cycles that it takes to activate the next bank of memory. It is the opposite of tRAS. The lower the timing, the better the performance, but it can cause instability.
tRFC Timing: Row Refresh Cycle Timing. This determines the amount of cycles to refresh a row on a memory bank. If this is set too short it can cause corruption of data and if it is too high, it will cause a loss in performance, but increased stability.
tRW Timing: Write Recovery Time. The amount of cycles that are required after a valid write operation and precharge. This is to insure that data is written properly.
tRTW/tRWT Timing: Read to Write Delay. When a write command is received, this is the amount of cycles for the command to be executed.
tWTR Timing: Write to Read Delay. The amount of cycles required between a valid write command and the next read command. Lower is better performance, but can cause instability.
tREF Timing: The amount of time it takes before a charge is refreshed so it does not lose its charge and corrupt. Measured in micro-seconds (µsec).
tWCL Timing: Write CAS number. Write to whatever bank is open to be written too. Operates at a rate of 1T, but can be set to others. It does not seem to work with other settings than 1T on DDR. DDR2 is different though.
Timings vs. Speed (throughput):
It is important to note that all timings are relative to clock cycle. What this means is, the values stated for all the timings below are only valid for the speed that they are currently running. It is helpful to know how to calculate latency in nanoseconds in order to have a truly accurate measure of latency. For example:
If you have a DDR module that is rated for 2-2-2-6 at DDR-400, the actual CAS latency in nanoseconds is calculated thusly:(1)/(Bus Speed) = Time period for one cycle
So:
(CAS Latency in cycles)*(1)/(Bus Speed)= CAS Latency as a period of time.
Simplified:
(CAS Latency in cycles)/(Bus Speed) = CAS Latency in time.
To take our above example:
(2)/(200,000,000) = 10ns.
It is more correct to say, that in this case, we have a CAS Latency of 10ns.
What we can do with this value is, we can compare it to say, CAS 2.5 at DDR-500:
(2.5)/(250,000,000) = 10ns.
Contrary to popular myth, CAS 2 @ DDR-400 is identical to CAS 2.5 @ DDR-500 in terms of latency. A quick rule of them for judging latencies is as follows;CAS 2 DDR-400 = 10ns
CAS 2.5 DDR-500 = 10ns
CAS 4 DDR2-800 = 10ns
CAS 5 DDR2-1000 = 10ns
CAS 6 DDR2-1200 = 10ns
CAS 7 DDR3-1400 = 10ns
CAS 8 DDR3-1600 = 10ns
All of the above are identical in terms of latency. The same method can be used to compare other latencies as well.
The difference between AMD and Intel in terms of memory performance:
The common wisdom is that “Intel loves bandwidth and AMD loves low timings.” The reason this is the case has to do with two different approaches in handling memory.
Intel uses an offshore memory controller in the northbridge that runs at a much slower speed than the CPU. What this allows Intel to do is incorporate very large L2 and L3 caches onto the CPU. L2 and L3 caches have an order of magnitude better latency than RAM memory does, so as long as these caches can be fed, the latency of RAM can be effectively hidden. Once a cache is exhausted however, the latencies are felt force. The higher the bandwidth of the RAM, the better the caches can be kept filled.
AMD sacrifices cache sizes for an integrated memory controller that runs at the speed of the CPU. What this means is, the caches will empty quicker, but once they do, the overall performance will not be affected as much.
In short, the Intel architecture is fastest for read accesses that fit in the large cache, but slower for more intensive applications that may exhaust the cache’s resources, while AMD sacrifices cache performance for overall memory performance.
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So the next section I will discuss is overclocking. I will discuss the procedure for overclocking as well as precautions and numerical and real life differences. Ram overclocking is very easy. Most of these figures will be able to be found using a simple household calculator. Most of the overclocking process (for RAM at least) is repetitive trial and error with memory testing in between adjustments. If that doesn't sound like your particular brand of whiskey then feel free to skip over this section. This is non-essential information. Note that in this section it is assumed that you have non-OEM parts in your PC and that you are not worried about voiding warranties.
For this section I am only going to discuss the conventional method of overclocking the ram, which involves the BIOS and will only work for motherboards that support manual settings of either the FSB or the RAM frequency or both. Also I should mention that this is my knowledge based on Intel based boards only because I have absolutely no experience with anything that is AMD.
Okay, it basically works like this: The first step in overclocking the RAM is to find out what speed your FSB is running at. We are going to go with 200mhz as an example throughout this tutorial.
When you have a FSB of 200mhz, and your RAM is rated for DDR2-800 (400MHz), then your ram would be running at a ratio of 1:2 of CPU:RAM. If you were to raise the front side bus to 250mhz then not only would you overclock your ram you woud also overclock your CPU (your ram would effectively be running at 500mhz or DDR2-1000) This however IS NOT TRUE FOR THE CPU! The front side bus of the cpu is not how fast your CPU is running. This is true because the CPU uses multipliers.
CPU speed is calculated like this:
FSB x Multiplier= Speed in mhz
200x9 = 1800mhz or 1.8ghz
Here are come charts that have various multipliers and dividers:
overclock.net/amd_memory....html
Some motherboards allow you to set different ratios of CPU:RAM which allow you to overclock the CPU and RAM at propotionally different intervals. If you had a FSB of 266mhz and you wanted your RAM to run at DDR2-1066mhz (533MHz) all you would have to do is set a ratio of 1:2 (CPU:RAM) Playing with these ratios will give you different overclocks. When overclocking, highest CPU FSB is the ultimate goal.
The procedure is as follows: This is where the redundancy comes rollin on in. First leave your timings as loose as possible and find the max mhz that your RAM will run at, then tighten the timings. To do that, raise the FSB buy say 10 or 15mhz each time, run memtest86+ all the way through, and repeat. When you start to see errors you have two options; you can decrease your overclock until you stop recieving errors or you can increase the voltage to the memory and keep going up until you reach the same roadblock. The process is the same for the CPU, except that the CPU frequency increases at a different rate. (which is FSBxCPU Multiplier) It will most likely be necessary for you to use a CPU:RAM ratio or to raise the voltage of the CPU when you overclock the RAM, assuming that you want to achieve relatively high RAM overclocks. ***NOTE THAT YOU MAY MAX OUT YOUR MEMORY CONTROLLER WHICH WILL HAULT YOUR OVERCLOCKING AT A CERTAIN SPEED***
It may also be necessary to increase more voltages than just RAM (vdimm), when increasing the FSB you might need more power after a substantial increase. Some higher end boards allow voltage adjustments for the FSB as well as the north and south bridge. Without enough voltage to these things this will also cause instability so it would be a good idea to try these when RAM voltage increases aren't working any more.
So now the question is how fast does my RAM run stock, and how far will my RAM overclock.
The stock speed of your ram is based on its ratings. Here is a table that will explain what ram ratings equate to and such.
So how far will my RAM overclock? Well that all depends on three things primarily. The first is your memory controller, you have to have a memory controller that will support higher DRAM frequencies then what is currently being run on the PC. Next is the IC that the memory module uses. The best (at the current time) by general consensus seem to bee the Micron D9 series of chips(DDR2). Most of these chips have the ability to reach over 1000mhz easily. The third most important thing that will affect overclocking is the PCB, (printed circuit board). This is the most overlooked aspect of RAM. Tests have shown that high end PCB's will yeild as much as 90mhz more performance if not more! Brainpower pcb's and 6 layer pcb's are the best. If you want to know what IC or PCB that your ram is using or if you want to know what to buy for overclocking I highly recommend that you visit the sites below for a reference. IC's highlighted in green are good for overclocking, IC's highlighted in red are bad for overclocking, and non-highlighted IC's are moderate.
Reference for DDR, DDR2, and DDR3!
Well what about my RAM getting to hot???
Memory cooling has become very popular, most notably on video cards. The effectiveness of memory cooling on both system ram and video cards, however, is often cause for debate amongst forum posters. Does system memory get hot enough to require active cooling? A lot of this depends on the IC. For example, the older OCZ VX modules that supported DDR-500 speeds at 2-2-2-6, 3.2V required active cooling of some sort in order to hit rated speeds. For the double-sided Micron D9 modules, especially when running four modules, active air cooling is highly recommended when exceeding 2.0V. While cooling may do little to change your maximum overclock, it may be effective in extending the life, particulary on some Micron D9 modules. Premier manufacturers such as Corsair, Mushkin, and OCZ ship their modules with heatspreaders across the chips. They look very nice and are often solid copper or aluminum. There are even RAM modules that sell with heatspreaders that carry liquid flow across them and are meant to be integrated into an already functioning water cooling system. Several other companies sell ram cooling kits, and other solutions for modules that come without cooling. Ram sinks are pretty much the same as standard heatsinks for graphics chips and CPUs, except they're a lot smaller and tailored for RAM chip sizes. Although its worth mentioning that RAM sinks and varios forms of active cooling have been proven to do very little when performance is in question.
How much voltage is too much?
To put it simply, there is no definitive answer to this question, it varies in many aspects, like IC, PCB, vendor, rating, and RAM type. As a general rule of thumb though it is not good to expose your RAM to voltages that are increased 10% over stock voltage for long periods of time.
Other things to know about RAM overclocking.
You should know that not only does RAM overclocking void most every warranty on the planet, it also will shorten the life span of your RAM. The two main factors that influence this are heat and voltage. Higher voltages usually do more damage then heat but both should be considered equally important.
KNOW THIS!!!
Just because Johnny across the street has his RAM overclocked to 5 million mhz that doesn't mean that yours will do that too just because you have the same RAM. RAM overclocking and its overall outcome have more factors than just the RAM itself.
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In this section I will cover some very common questions about RAM and some if its workings. This section will contain a generalized FAQ type style as well as certain terminologies explained. Dual Channel, what exactly is dual channel? 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. When referring to dual channel memory, it is referring to how the motherboard uses RAM.
Individual modules have 64-bit interfaces, but many memory controllers have 128-bit interfaces. The 128-bit interface is divided into 64-bit channels, often times with two DIMM sockets assigned per channel.
Dual channel memory “kits” are often tested for optimal compatibility with each other, and are more likely to have the same ICs, however it is not a “necessity” to buy RAM in kits.
What are the requirements for dual-channel? The requirements for dual channel are pretty simple. You need a motherboard that has dual-channel capability and you **usually** need two identical RAM modules. Some motherboards are more lenient than others. Some let you have two chips that have the same density and speeds and some require you to have everything matching right down to the serial number, these are called "factory matched pairs".
Well who made my ram chips or IC's?
Well that can usually be answered one of two ways, one of which is alot more certain than the other. The most definitive way to find out what IC your memory module uses is to just look at the module itself. Take the RAM out of your computer and look at the number-code that is etched into the black chips, then search that number on google. If you have a heat-spreader covering the black chips you can either take it off (which usually voids the warranty) or you can move on to the less definitive method. The less definitive method is to use an online chart that has most RAM IC's documented but is missing a few and needs some updating. They can be found here for DDR, DDR2, and DDR3!
2x2gb vs 4x1gb? Which is better?
Well the performance of the two is pretty much the same. The only difference would possibly be overclocking potential. Overclocking potential might take a hit if the RAM controller is stressed too much, therefore limiting the overclock. Stress on the RAM controller comes from how many ranks of IC's it has to control. If you have 2x2gb sticks of RAM then they are likely dual sided (=2 ranks per stick), meaning there are RAM IC's on both sides of the stick. If you have 2 sticks of dual sided RAM then thats a total of 4 ranks. If you have 4x1gb then thats where the overclocking potential might take a hit. If you have single sided sticks thats still a total of 4 ranks (no extra stress). If you have dual sided then that is a total of 8 ranks. 8 ranks is a lot of stress for memory controllers and has been shown to limit overclocks.
Well what IC's are good and what IC's are bad?
That really depends on what you want to do with the memory module, all IC's are generally fine for common use and are manufactured so they will work just fine with the advertised settings. If you however are not going to be using them in a general manor and tend to overclock quite frequently then there are major differences in the IC's. For the DDR series of RAM, the most notorious overclocker's IC is the Samsung TCCD and the Winbond BH-5/CH-5/UTT line of chips. For the DDR2 series of chips, there are a few very reputable Micron IC's and they are all members of the Micron D9 series of IC's. For the DDR3 series one is really just as good as the other, there is not really much need to overclock these chips anyway because they are really fast enough out of the box. For reference here is a list of all the current Micron (common) IC's and their specs. Remember green indicates a good overclocker. Also you can find a picture based reference of common DDR2 chips here.
[center][center]DDR
Winbond BH: (old + new school)
basically the ram that has turned into a myth of sorts. normally does around 240-270MHz.. not great in itself, but the thing to remember is that it can do it at 2-2-2 timings. the downside is that it typically needs 3.2-3.5v to do that. Also, higher latencies do not help much.. forget about cas3, it shouldn't boot. cas2.5 often isn't as stable, or simply does not get many more MHz. Try not to go higher than 3.5-3.6v unless benching, and be sure that your system is up to taking that much voltage for long term use.
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UTT-CH:
Will adding more RAM to my computer make it faster?
That depends almost entirely on how much memory the tasks you do on your computer take. If you are running simple or older programs that simply are not memory intensive, additional memory largely cannot help you. But over time operating systems and applications tend to require (and therefore benefit from) increasing amounts of memory, and in most cases it's hard to have too much. 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 (see virtual memory below) 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. RAM is nothing more than an electronic storage area for data. RAM stores data like a hard drive but a hard drive is mechanical and is consequently alot slower in data transfer than RAM is. So this makes data storage alot faster. When you have to write data to the hard drive it slows down your computer. You need enough RAM to meet your maximum usage, but no more than this. If a program requires more memory then you have installed, free hard drive space will be converted into virtual memory. So why not use your 500GB hard drive for memory? Simple - speed. Your system will crawl and games stutter if you have to use virtual memory.
Average RAM speed: 8000MB/s xfer rate, 4ns latency (nanoseconds as in one billionth of a second)
Average Hard Drive speed: 60MB/s xfer rate, 14ms access time (milliseconds, as in one thousandth of a second)
However, you do not want too much, because it puts additional strain on the memory controller, overclocks worse and costs more. You only need to satisfy your maximum usage.
What is virtual memory?
This is a method of extending the available physical memory (RAM) on a computer. It basically partitions off a section of a hard drive and uses it in place of RAM. It uses this section to read and write data that was too large to fit into RAM. Virtual memory is drastically slower than RAM. If you are having to use the swap file/page file at all then that is when more RAM would improve computer speed.
Burning in RAM, what is it and does it really work?
Burning in ram is basically like breaking in an engine. You control all of the operating variables and run it in that state for a long period of time. This allows for it to perform better once the operating variables are changed. Burning in RAM is said like this. You overclock your RAM, then you burn it in. All thats doing is letting the RAM get really really comfortable operating at those specific variables. This allows for it to be overclocked in the same proportion alot easier. Does it really work? Well the short answer is yes, it does. It yeilds some of the highest overclocks but this method is should only really be implemented if you are an "overclocking junkie" and you are looking for your true maximum overclock. Another more common use for it is when you hit a wall when overclocking. It is very redundant work though.
Can I use faster rated RAM than my motherboard supports?
Well of course you can, there is a drawback of course, your RAM will run as fast as your motherboard can handle and not at its full potential. In this particular equation, the motherboard is the limiting factor.
What programs can I use to check my memory?
There a few pretty reliable programs out there that will let you check different things about your memory. If you just want to know what type of memory you are using and the SPD specs of the modules then you can use CPU-z. If you want to benchmark your memory then Sandra Lite is a good choice, this is made by Sisoft. If you want to see if your memory is having errors then there are two options for this, there is the less reliable software option, and the more reliable bootable dos option. The software version is memtest. The more reliable and thorough version is memtest86+. It should also be noted that even though they are both under the name of memtest, the are not however made by the same organization.The reason that the software version is less reliable is because it doesn't have the ability to check the RAM that is being used by the operating system and currently running programs.
RAM defraggers, theory and actual impacts:
RAM defraggers in theory are designed to not "defrag" the memory but to push all of the RAM to a minimized and compressed level while in the RAM. This is actually a bad thing because it could lead to data corruptions and it is actually taking RAM away from the already running programs. I advise against these types of programs.
Whats the difference between buffered and unbuffered DIMMs?
High density DIMMs have lots of chips on them and therefore possess a higher capacitive load on the address and control signals in comparison to lower density DIMMs. Some designers use redrive buffers on the DIMM to boost the signals to reduce system loading when compared to the same high density module without buffers. But the buffers introduce a small delay into the electrical signal, so adding buffers to a standard density module would have the effect of slowing down the signal, compared to the same low density module without buffers. FBDIMMS are only common in server applications and are not necessary for desktop/workstation applications. The purpose of an FBDIMM is to preserve data integrity. (Maintaining data integrity in a server is essential.)
What is SLI/crossfire approved RAM and is it necessary?
SLI and crossfire approved memory is nothing more than a big marketing scam really. SLI/crossfire approved RAM is made with a thing called an EPP. An EPP is an "enhanced performance profile" which is nothing more than another on-chip SPD entry. (see SPD below) You do not need SLI/Crossfire approved RAM to use a SLI or crossfire system. The EPP usually doesn't even work unless you have a Nvidia or Ati chipset that supports it. (which most don't) Its purpose is to not only provide enhanced performance when enabled but to ensure that when overclocking the system, the RAM stays at its rated frequency, voltages, and timings. This is bad news to an overclocker however you can disable without really any hassle. If you are looking at buying an SLI/Crossfire approved RAM module I suggest that you look at what the EPP provides so you can se it as a reference to what the RAM module is capable of. The timings rated in the EPP are perfectly attainable on that RAM module without having the EPP enabled. THIS IS WHY ITS A SCAM. The EPP is only telling you the true performance of the RAM module. My advice to overclockers is to keep it disabled (if it is even enabled), forget its there, and overclock like h***!
What is an SPD, EPP, and XMP?
An SPD is a serial presence detect. An SPD is sort-of like a set of rules for the RAM. An SPD is a set of entries on the RAM module that tell the motherboard what timings and voltages to run at while at different frequencies. (e. g.= SPD=4-4-4-15@800mhz) They are all usually based on JEDEC standards. An EPP is an enhanced performance profile. It is marketed on SLI/Crossfire approved memory modules. An EPP is nothing more than an SPD that can only be read on certain chipsets from Nvidia and Ati. If the chipset cannot read it then it is ignored by the motherboard and it uses the basic SPD settings. The enhanced performance profile settings are easily achieved with manual settings. The purpose of an EPP is to be able to have it auto-configured to those settings. An XMP is intels version of EPP. XMP stands for extreme memory profile. It is once again just another marketing scam because you can always just use the manual settings to achieve the XMP settings. The XMP RAM modules are compatible with Intel's X38 chipset.
Whats the difference between 72bit and 64 bit/ what is ECC?
72 bit memory is commonly known as ECC memory. It has an additional 8 bits for Error Correction Check 64 bit memory is non-ECC. 72 bit configurations are typically found in 168 pin DIMMs whereas 64bit configurations are found abundantly.
Why can't i see/use 4gb of RAM?
Well this is because 32bit operating systems (most common type of os) only have enough memory address space for 4gb. This doesn't mean its all going to your RAM though. This also includes graphics RAM, networking peripherals, pci cards, and the like. You will only be able to see 3.2~3.5gb of RAM on a 32bit operating system. High end computer users might be using a 64bit operating system which natively supports addressing for much larger amounts of RAM. The current maximums for windows operating systems are as follows: - Windows XP Home: 4GB
- Windows XP Professional: 4GB
- Windows XP 64-bit: 128GB
- Windows Vista Home Basic: 4GB
- Windows Vista Home Basic 64-bit: 8GB
- Windows Vista Home Premium: 4GB
- Windows Vista Home Premium 64-bit: 16GB
- Windows Vista Ultimate: 4GB
- Windows Vista Ultimate 64-bit: 128GB+
- Windows Vista 32-bit: 4GB
- Windows Vista 64-bit: 128GB+
This has been a presentation by Derrick Durham with the help of the following websites. I hope you like my work...what a waste of 9 hours of my life. Let me know if im forgetting anything or if something should be changed. I decided to write and share this because RAM seems to be one of the components of the pc that average users and overclockers know the least about. Everything that I have provided on this post took me about one and a half months to learn. THANKS FOR READING!!
All you guys can thank Ether.real for reviewing and helping me improve this guide.
Wikipedia.org
DSLReports.com
RAMlist.ath.cx
techpowerup.com
Pcstats.com
extremeoverclocking.com
eclipseoc.com
cpuid.com
HCIdesign.com
sisoftware.net
memtest.org
buycomputermemory.com
crucial.com
overclock.net
Last edited by D-Rock : 06-23-2009 at 04:47 PM.
Reason: updating
|
02-28-2008, 09:16 PM
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