dav-ID
16-12-07, 03:30
Moderators and all , please rip/edit/copy/pase this as you wish perhaps after a tidy up and a look over ,somebody could make a sticky faq out of it.
Part 1 Points to consider when choosing memory for your PC.
Module type .
This is the physical arrangement of the memory chips and the interface PCB size and number of pins ,most of the time these standards are paired to a CPU type as manufactures roll out all their new technologies at the same time.this is known as a "platform" Socket7 CPU paired with memory Simms ,Intel P4 CPU paired with memory RIMMs and so on.The motherboards northbridge chip is usually the systems memory controller and this denotes the type of module used So the Specs of your chosen motherboard will include the type of memory module required. (At the moment most boards seem to use DDR2 modules with DDR3 on some top end motherboards.)
Memory size.
You need to decide how much memory you are going to need , Some motherboards and OS have upper limits so check before buying to much.
32bit vista is capped at 4gb / 32bit XP is caped at 2gb with a mod to 3gb and 4gb
See microsofts website;
http://msdn2.microsoft.com/en-us/library/aa366778.aspx
Memory speed .
This is measured in Mhz and is the speed at which the memory controller can talk to the memory module ,so higher numbers equals faster memory transfers
Because of a technology named double data rate "DDR2" four times as much data can be sent compared to standard SDRAM which can lead to confusion when manufactures label 400mhz modules as 800mhz modules(when infact the chips are running at 200mhz) in order to correct identify the module it is better to look for the PC2 or DDR2 grading standard it always starts with "PC2" or the "DDR2"
Heres a list to help identify them ;
PC2 name - DDR2 Name - Memory clock - Bus clock - Data transfers per second - Peak transfer rate
PC2-3200 - DDR2-400 --- 100 MHz ----- 200 MHz --- 400 Million -------------- 3200 MB/s
PC2-4200 - DDR2-533 --- 133 MHz ----- 266 MHz --- 533 Million -------------- 4264 MB/s
PC2-5300 - DDR2-667 --- 166 MHz ----- 333 MHz --- 667 Million -------------- 5336 MB/s
PC2-6400 - DDR2-800 --- 200 MHz ----- 400 MHz --- 800 Million -------------- 6400 MB/s
PC2-8500 - DDR2-1066 -- 266 MHz ----- 533 MHz -- 1066 Million -------------- 8500 MB/s
As you can see the "DDR2" name relates to theoretical transfers per second in mhz and the "PC2" naming relates to the theoretical peak transfers per second.
when i say theoretical I mean expect to get about 300mb/s /1,000mb/s lower than the spec's above ,If running duel channel expect an increase between 200mb/s to 1,000mb/s as the specs above are for single channel.
Links;
http://en.wikipedia.org/wiki/DDR2_SDRAM
Dual channel.
Dual channel configuration consists of two independent memory controllers ,If your mother board supports dual channel the memory banks on the board will be color coded
so that you may add a pair on memory modules (one stick on each controller) to increase memory transfer to the CPU , be warned this shouldn't be seen as "Raid Array for memory" it will not double the performance!
In fact depending on the type of tests expect a performance increase between 10% to 30%.
links;
http://en.wikipedia.org/wiki/Dual_channel
Memory timing's
Although PC2-6400 memory can be talked to at 800,000,000 pules per second it can not store data in memory that fast ,some of those pulse's are simple commands like blank,refresh,address,.Memory timing numbers like 5-5-5-16 give you an idea of how many pules it takes before data is read/written from memory, natural lower numbers here are better but it is not as important as memory speed and duel channel
links;
http://en.wikipedia.org/wiki/CAS_latency
http://www.dewassoc.com/performance/memory/memory_speeds.htm
Memory overclocking & optimization
Manufactures of CPU & memory chips have different business models so each have tackled overclocking differently ,CPU manufactures developer a chip design then tap the same chip out at various performance levels sometimes making only minor revisions .this means a manufacture can have a product line from a £30 to £150 from basically the same chip design. For years memory manufacturers didn't have anything like this product scaling , they put chips on PCB's to meet a speed standard for the currant motherboards and set the price according to cost/quality of the chips used.
The SPD rating is a way for manufactures to diversify their product rage and a way for customers to have the memory that is automatically configured by the motherboard, As the SPD information is written on a small Eprom on each memory module at the time they're assembled onto the PCB it potential allows manufactures to sell two similar products from identical ram chips simply by adding different SPD information thus copying the business model of the CPU manufactures.this isn't a bad situation it means their are more product to choose from but is also means you may purchase a budget modual that overclocks very well.
Next enters the EPP rating this information is stored on the same Eprom next to the SPD data .EPP is the manufactures recommended maximum operating limits. If the motherboard supports EPP configuration
selecting EPP in the bios will improve memory transfer speed by safely overclocking to manufactures guidelines , If the motherboard dose not support EPP but the bios has manual options for memory voltage,timing & speed(mhz) you will be able to setup the memory manually for the same performance level as EPP , If your motherboard lacks ether auto EPP or manual memory voltage,timing & speed(mhz) settings the memory will run at the lower SPD configuration , you can still buy EPP memory but don't expect as same performance as written on the packaging as manufacture usually print the EPP timings on their products, to find the SPD timings of EPP modules visit the manufactures website and lookup the specific memory module.
links;
http://en.wikipedia.org/wiki/Enhanced_Performance_Profiles
http://en.wikipedia.org/wiki/Serial_Presence_Detect
http://www.corsair.com/news/press_release.aspx?id=147110
Part 2 Possible consideration that affect your memory requirements
Thats the basics now you need to choose a product ,At the moment most motherboards are DDR2 based so that take care of the first point. as for Memory size that depends on the programs you run if you're a gamer check the requirements of the latest games , or in winXP you could run your main programs then bring up task manage and note the peak memory usage.
The home users that tend benefit from fast memory are gamers and video editors these applications can require lots of random access to memory in a time critical situation ,gamers should be aware that the GRFX ,HD's and sound cards all have (DMA) thats Direct Memory Access (http://en.wikipedia.org/wiki/Direct_Memory_Access) to the core memory as well a the CPU this can put a strain on random access to memory. Video editors that are compositing lots of video footage with titles and filters,fades and wipes in programs like AfterFX ,Final cut pro will create lots of uncompressed cached pre render's , while its more important to have enough memory to avoid swapping renders to disk having fast memory will make the time line feel lighter when hitting those cached pre-renders, generally these are small gains but the price difference between them is small also.
If the PC is used for Internet,Chat,Email Audio,Ipod,DVDriping and playback you would be better spending less on memory and more on the hard drive or better speakers as these programs don't have large memory footprints and multimedia encoding and decoding operations are handled in the L2 cache of the CPU efficiently.
If fast memory is still a priority the best point to start with is Duel channel if your motherboard supports this its almost a "Free 30% improvement" as you simply need to buy 2 smaller capacity modules rather than one single modules you can buy a pair of modules in a duel kit or simply buy two modules of same type, if for some reason they workout cheaper.
The next consideration is the speed rating once again gamers should buy the highest spec there boards support everybody else should expect to see less punch for there money
Most customers should have a good idea of performance level they require
and as is often the case with computer components the faster/newer products do not cost much more so you may end up purchasing the faster memory anyway,
Only continue reading if you want to squeeze the last drop of performance from the memory
Ok if you have got to the memory timings & optimization stage you're ether a hardcore gamer or building a small multimedia rendering farm :) Memory timings are the processing delay of the modules
Just like gear wheels they change the input speed to something faster/slower than what you starting with thus memory uses timings to run at a slower speed.
Programs understand this and when possible use the CPU cach to aviod the slowdown by the delay accessing memory, memory delay only affects large ammounts of random access to memory
The simplest analagy is the hard-disc seek times once the HD head has seeked to the corect places data moves very fast and only when asked for data in a diferant location do you get a drop in datarate
memory delay acts like seektime but dosent get fragmented as much as a harddisc so the problem is reduced ,main point to remember is that timings are not as important as overall memory speed but if
your GRFX is intergrated into the motherboard using the same memory for GPU & CPU or running duel GRFX card or if you just want the fastest memory money can buy timings are the very last thing you cant do to squeesz more performance out of a system ,wether its worth the small increase is up to you.
Part 1 Points to consider when choosing memory for your PC.
Module type .
This is the physical arrangement of the memory chips and the interface PCB size and number of pins ,most of the time these standards are paired to a CPU type as manufactures roll out all their new technologies at the same time.this is known as a "platform" Socket7 CPU paired with memory Simms ,Intel P4 CPU paired with memory RIMMs and so on.The motherboards northbridge chip is usually the systems memory controller and this denotes the type of module used So the Specs of your chosen motherboard will include the type of memory module required. (At the moment most boards seem to use DDR2 modules with DDR3 on some top end motherboards.)
Memory size.
You need to decide how much memory you are going to need , Some motherboards and OS have upper limits so check before buying to much.
32bit vista is capped at 4gb / 32bit XP is caped at 2gb with a mod to 3gb and 4gb
See microsofts website;
http://msdn2.microsoft.com/en-us/library/aa366778.aspx
Memory speed .
This is measured in Mhz and is the speed at which the memory controller can talk to the memory module ,so higher numbers equals faster memory transfers
Because of a technology named double data rate "DDR2" four times as much data can be sent compared to standard SDRAM which can lead to confusion when manufactures label 400mhz modules as 800mhz modules(when infact the chips are running at 200mhz) in order to correct identify the module it is better to look for the PC2 or DDR2 grading standard it always starts with "PC2" or the "DDR2"
Heres a list to help identify them ;
PC2 name - DDR2 Name - Memory clock - Bus clock - Data transfers per second - Peak transfer rate
PC2-3200 - DDR2-400 --- 100 MHz ----- 200 MHz --- 400 Million -------------- 3200 MB/s
PC2-4200 - DDR2-533 --- 133 MHz ----- 266 MHz --- 533 Million -------------- 4264 MB/s
PC2-5300 - DDR2-667 --- 166 MHz ----- 333 MHz --- 667 Million -------------- 5336 MB/s
PC2-6400 - DDR2-800 --- 200 MHz ----- 400 MHz --- 800 Million -------------- 6400 MB/s
PC2-8500 - DDR2-1066 -- 266 MHz ----- 533 MHz -- 1066 Million -------------- 8500 MB/s
As you can see the "DDR2" name relates to theoretical transfers per second in mhz and the "PC2" naming relates to the theoretical peak transfers per second.
when i say theoretical I mean expect to get about 300mb/s /1,000mb/s lower than the spec's above ,If running duel channel expect an increase between 200mb/s to 1,000mb/s as the specs above are for single channel.
Links;
http://en.wikipedia.org/wiki/DDR2_SDRAM
Dual channel.
Dual channel configuration consists of two independent memory controllers ,If your mother board supports dual channel the memory banks on the board will be color coded
so that you may add a pair on memory modules (one stick on each controller) to increase memory transfer to the CPU , be warned this shouldn't be seen as "Raid Array for memory" it will not double the performance!
In fact depending on the type of tests expect a performance increase between 10% to 30%.
links;
http://en.wikipedia.org/wiki/Dual_channel
Memory timing's
Although PC2-6400 memory can be talked to at 800,000,000 pules per second it can not store data in memory that fast ,some of those pulse's are simple commands like blank,refresh,address,.Memory timing numbers like 5-5-5-16 give you an idea of how many pules it takes before data is read/written from memory, natural lower numbers here are better but it is not as important as memory speed and duel channel
links;
http://en.wikipedia.org/wiki/CAS_latency
http://www.dewassoc.com/performance/memory/memory_speeds.htm
Memory overclocking & optimization
Manufactures of CPU & memory chips have different business models so each have tackled overclocking differently ,CPU manufactures developer a chip design then tap the same chip out at various performance levels sometimes making only minor revisions .this means a manufacture can have a product line from a £30 to £150 from basically the same chip design. For years memory manufacturers didn't have anything like this product scaling , they put chips on PCB's to meet a speed standard for the currant motherboards and set the price according to cost/quality of the chips used.
The SPD rating is a way for manufactures to diversify their product rage and a way for customers to have the memory that is automatically configured by the motherboard, As the SPD information is written on a small Eprom on each memory module at the time they're assembled onto the PCB it potential allows manufactures to sell two similar products from identical ram chips simply by adding different SPD information thus copying the business model of the CPU manufactures.this isn't a bad situation it means their are more product to choose from but is also means you may purchase a budget modual that overclocks very well.
Next enters the EPP rating this information is stored on the same Eprom next to the SPD data .EPP is the manufactures recommended maximum operating limits. If the motherboard supports EPP configuration
selecting EPP in the bios will improve memory transfer speed by safely overclocking to manufactures guidelines , If the motherboard dose not support EPP but the bios has manual options for memory voltage,timing & speed(mhz) you will be able to setup the memory manually for the same performance level as EPP , If your motherboard lacks ether auto EPP or manual memory voltage,timing & speed(mhz) settings the memory will run at the lower SPD configuration , you can still buy EPP memory but don't expect as same performance as written on the packaging as manufacture usually print the EPP timings on their products, to find the SPD timings of EPP modules visit the manufactures website and lookup the specific memory module.
links;
http://en.wikipedia.org/wiki/Enhanced_Performance_Profiles
http://en.wikipedia.org/wiki/Serial_Presence_Detect
http://www.corsair.com/news/press_release.aspx?id=147110
Part 2 Possible consideration that affect your memory requirements
Thats the basics now you need to choose a product ,At the moment most motherboards are DDR2 based so that take care of the first point. as for Memory size that depends on the programs you run if you're a gamer check the requirements of the latest games , or in winXP you could run your main programs then bring up task manage and note the peak memory usage.
The home users that tend benefit from fast memory are gamers and video editors these applications can require lots of random access to memory in a time critical situation ,gamers should be aware that the GRFX ,HD's and sound cards all have (DMA) thats Direct Memory Access (http://en.wikipedia.org/wiki/Direct_Memory_Access) to the core memory as well a the CPU this can put a strain on random access to memory. Video editors that are compositing lots of video footage with titles and filters,fades and wipes in programs like AfterFX ,Final cut pro will create lots of uncompressed cached pre render's , while its more important to have enough memory to avoid swapping renders to disk having fast memory will make the time line feel lighter when hitting those cached pre-renders, generally these are small gains but the price difference between them is small also.
If the PC is used for Internet,Chat,Email Audio,Ipod,DVDriping and playback you would be better spending less on memory and more on the hard drive or better speakers as these programs don't have large memory footprints and multimedia encoding and decoding operations are handled in the L2 cache of the CPU efficiently.
If fast memory is still a priority the best point to start with is Duel channel if your motherboard supports this its almost a "Free 30% improvement" as you simply need to buy 2 smaller capacity modules rather than one single modules you can buy a pair of modules in a duel kit or simply buy two modules of same type, if for some reason they workout cheaper.
The next consideration is the speed rating once again gamers should buy the highest spec there boards support everybody else should expect to see less punch for there money
Most customers should have a good idea of performance level they require
and as is often the case with computer components the faster/newer products do not cost much more so you may end up purchasing the faster memory anyway,
Only continue reading if you want to squeeze the last drop of performance from the memory
Ok if you have got to the memory timings & optimization stage you're ether a hardcore gamer or building a small multimedia rendering farm :) Memory timings are the processing delay of the modules
Just like gear wheels they change the input speed to something faster/slower than what you starting with thus memory uses timings to run at a slower speed.
Programs understand this and when possible use the CPU cach to aviod the slowdown by the delay accessing memory, memory delay only affects large ammounts of random access to memory
The simplest analagy is the hard-disc seek times once the HD head has seeked to the corect places data moves very fast and only when asked for data in a diferant location do you get a drop in datarate
memory delay acts like seektime but dosent get fragmented as much as a harddisc so the problem is reduced ,main point to remember is that timings are not as important as overall memory speed but if
your GRFX is intergrated into the motherboard using the same memory for GPU & CPU or running duel GRFX card or if you just want the fastest memory money can buy timings are the very last thing you cant do to squeesz more performance out of a system ,wether its worth the small increase is up to you.