What is PC3-XXXX

[RDKells]

Can someone explain PC3-XXXX to me please?

I can't find an explaination, I learn better with examples, is it to do with clock speed?

I've noticed a PC3-10600 module is 1333mhz but a PC3-12800 is 1666mhz?

I'm confused,

Thanks,
Ryan.

On a side note, is there any performance difference between these 2; Both are 1600mhz and CL9.

http://www.amazon.co.uk/dp/B004G7XQC2/?tag=pcp0f-21

http://www.amazon.co.uk/Corsair-CMZ8GX3M2A1600C9-Vengeance-Performance-Desktop/dp/B004CRSM4I/ref=sr_1_1?s=computers&ie=UTF8&qid=1380247769&sr=1-1&keywords=corsiar+vengence

 

[cklaubur]

The numbers after PC3 is the total system bandwidth. It is calculated by taking the bus speed, multiplying by 4 (DDR3 runs at 4 times the bus speed), then multiplying by 2 (DDR transfers twice for each clock tick), multiplying by 64 (64-bit wide memory bus), then finally dividing by 8 to get the bandwidth in megabytes/second.

The two links you provided should perform the same.

Casey

 

[RDKells]

Thanks for taking the time to answer Casey but I'm still confused.

The BUS speed of what? The RAM? Please can you give an example?

Thanks,
Ryan.

 

[cklaubur]

It's a bit confusing because the actual memory bus speed is never advertised. The PC3-10600 module you mentioned in your original post has an effective memory bus speed of 1333 MHz. To get the actual speed, you need to divide by 4 (because DDR3 by definition transfers 4 times the information of standard DDR), then divide that result by 2 (since DDR by definition transfers information twice for each tick of the memory clock).

As a result, the actual memory bus speed of the PC3-10600 module is 166 MHz (1333/4 equals 333, then 333/2 equals 166). It does require a bit of math, however, it is something that doesn't need to be known very ofter since most everything is based on the effective memory speed.

Casey

 

[Tradesman1]

In short, it's the hypothetical memory bandwidth in MT/s (Mega Transfers per Second) which doesn't mean a lot as you will never completely use all your DRAM at once, thus filling out the bandwidth , which is why it's considered Hypothetical

 

[AGx-07_162]

Thanks for taking the time to answer Casey but I'm still confused.

The BUS speed of what? The RAM? Please can you give an example?

Thanks,
Ryan.

Lets look at a RAM module marketed as PC3 6400:

This is about the slowest RAM you can find but I chose it for simplicity purposes.

Now, lets define something real quick. Clock Speed: the operating speed of a computer or its microprocessor, defined as the rate at which it performs internal operations and expressed in cycles per second (megahertz).

Lets define one more thing: Double Data Rate(DDR): It is an advanced version of SDRAM, a type of computer memory. DDR-SDRAM, sometimes called "SDRAM II," can transfer data twice as fast as regular SDRAM chips. This is because DDR memory can send and receive signals twice per clock cycle.

With that out of the way, lets start at PC1-#### and work our way up to PC3-#### and the example up there to break down how these numbers work.

DDR
This nice, slow RAM has a 100MHz Memory Clock speed, meaning it can process 200 Million operations per second. Remember, since we're talking about DDR-SDRAM, the data rate is doubled (essentially 100 MHz * 2). Though it has a clock speed of 100 MHz, for marketing purposes, this will be marketed at 200 MHz (or DDR-200), it's effective clock based on its "Double Data Rate".

Now, the Module Name (PC-####) is based on transfer rate and is actually the PC sped rating. You're going to multiply the effective clock speed by 8, the width (in Bytes) of all DDR SDRAM sticks. In the example above, you'd be taking the 200 * 8 = 1600. Slap a PC in front of that and you have PC1600.

Why is 8 the multiplyer you ask? Modern DRAM is 64 "bits" wide. Bit's are usually convered into Bytes and since there are 8 bits in a Byte, divide 64 by 8 and you get 8. The 64-bit width converts into 8-bytes (your multiplier).

DDR 2

When we're talking about DDR 2, it's twice as fast as DDR as it clock doubles the I/O circuits on the chips, speeding up the input/output and adding special buffers.

So that same 100 MHz clock speed translates into (100 MHz * 2) 2 = 400 MHz (or DDR2-400). Multiply that by 8 and (and slap a PC2 in front) you have PC2-3200.

DDR3

DDR3 doubles the buffer of DDR2 from 4-bits to 8-buts, giving it a bandwidth boost. There are also some other features thrown in there that I wont get into.

So that same 100 MHz clock speed translates into ((100 MHz * 2) 2)2 = 800 MHz (or DDR3-800). Multiply that by 8 and (and slap a PC3 in front) you have PC3-6400.

That should give you a basic understanding of how these numbers work. The bottom line doesn't seem to matter to me as I'm always looking for the fastest my board supports (and I can afford) so the "how it works" matters little to me.

 

[Aragoneu]

Lets look at a RAM module marketed as PC 6400:

This is about the slowest RAM you can find but I chose it for simplicity purposes.

Now, lets define something real quick. Clock Speed: the operating speed of a computer or its microprocessor, defined as the rate at which it performs internal operations and expressed in cycles per second (megahertz).

Lets define one more thing: Double Data Rate(DDR): It is an advanced version of SDRAM, a type of computer memory. DDR-SDRAM, sometimes called "SDRAM II," can transfer data twice as fast as regular SDRAM chips. This is because DDR memory can send and receive signals twice per clock cycle.

With that out of the way...

DDR
This nice, slow RAM has a 100MHz Memory Clock speed, meaning it can process 200 Million operations per second. Remember, since we're talking about DDR-SDRAM, the data rate is doubled (essentially 100 MHz * 2). Though it has a clock speed of 100 MHz, for marketing purposes, this will be marketed at 200 MHz (or DDR-200), it's effective clock based on its "Double Data Rate".

Now, the Module Name (PC-####) is based on transfer rate and is actually the PC sped rating. You're going to multiply the effective clock speed by 8, the width (in Bytes) of all DDR SDRAM sticks. In the example above, you'd be taking the 200 * 8 = 1600. Slap a PC in front of that and you have PC1600.

Why is 8 the multiplyer you ask? Modern DRAM is 64 "bits" wide. Bit's are usually convered into Bytes and since there are 8 bits in a Byte, divide 64 by 8 and you get 8. The 64-bit width converts into 8-bytes (your multiplier).

DDR 2

When we're talking about DDR 2, it's twice as fast as DDR as it clock doubles the I/O circuits on the chips, speeding up the input/output and adding special buffers.

So that same 100 MHz clock speed translates into (100 MHz * 2) 2 = 400 MHz (or DDR2-400). Multiply that by 8 and (and slap a PC2 in front) you have PC2-3200.

DDR3

DDR3 doubles the buffer of DDR2 from 4-bits to 8-buts, giving it a bandwidth boost. There are also some other features thrown in there that I wont get into.

So that same 100 MHz clock speed translates into ((100 MHz * 2) 2)2 = 800 MHz (or DDR3-800). Multiply that by 8 and (and slap a PC3 in front) you have PC3-6400.

That should give you a basic understanding of how these numbers work. The bottom line doesn't seem to matter to me as I'm always looking for the fastest my board supports (and I can afford) so the "how it works" matters little to me.

That as actually very informative. Thanks.

 

[RDKells]

AGX - Marvellous, thanks.

It wasn't essentially how it worked more what PC3 was exactly, thank you for the concise answer I understand it now.

Ryan.

 

[theqasim95]

Thanks for taking the time to answer Casey but I'm still confused.

The BUS speed of what? The RAM? Please can you give an example?

Thanks,
Ryan.

Lets look at a RAM module marketed as PC3 6400:

This is about the slowest RAM you can find but I chose it for simplicity purposes.

Now, lets define something real quick. Clock Speed: the operating speed of a computer or its microprocessor, defined as the rate at which it performs internal operations and expressed in cycles per second (megahertz).

Lets define one more thing: Double Data Rate(DDR): It is an advanced version of SDRAM, a type of computer memory. DDR-SDRAM, sometimes called "SDRAM II," can transfer data twice as fast as regular SDRAM chips. This is because DDR memory can send and receive signals twice per clock cycle.

With that out of the way, lets start at PC1-#### and work our way up to PC3-#### and the example up there to break down how these numbers work.

DDR
This nice, slow RAM has a 100MHz Memory Clock speed, meaning it can process 200 Million operations per second. Remember, since we're talking about DDR-SDRAM, the data rate is doubled (essentially 100 MHz * 2). Though it has a clock speed of 100 MHz, for marketing purposes, this will be marketed at 200 MHz (or DDR-200), it's effective clock based on its "Double Data Rate".

Now, the Module Name (PC-####) is based on transfer rate and is actually the PC sped rating. You're going to multiply the effective clock speed by 8, the width (in Bytes) of all DDR SDRAM sticks. In the example above, you'd be taking the 200 * 8 = 1600. Slap a PC in front of that and you have PC1600.

Why is 8 the multiplyer you ask? Modern DRAM is 64 "bits" wide. Bit's are usually convered into Bytes and since there are 8 bits in a Byte, divide 64 by 8 and you get 8. The 64-bit width converts into 8-bytes (your multiplier).

DDR 2

When we're talking about DDR 2, it's twice as fast as DDR as it clock doubles the I/O circuits on the chips, speeding up the input/output and adding special buffers.

So that same 100 MHz clock speed translates into (100 MHz * 2) 2 = 400 MHz (or DDR2-400). Multiply that by 8 and (and slap a PC2 in front) you have PC2-3200.

DDR3

DDR3 doubles the buffer of DDR2 from 4-bits to 8-buts, giving it a bandwidth boost. There are also some other features thrown in there that I wont get into.

So that same 100 MHz clock speed translates into ((100 MHz * 2) 2)2 = 800 MHz (or DDR3-800). Multiply that by 8 and (and slap a PC3 in front) you have PC3-6400.

That should give you a basic understanding of how these numbers work. The bottom line doesn't seem to matter to me as I'm always looking for the fastest my board supports (and I can afford) so the "how it works" matters little to me.

thanks

 

[Mark_MaB]

Thanks for taking the time to answer Casey but I'm still confused.

The BUS speed of what? The RAM? Please can you give an example?

Thanks,
Ryan.

Lets look at a RAM module marketed as PC3 6400:

This is about the slowest RAM you can find but I chose it for simplicity purposes.

Now, lets define something real quick. Clock Speed: the operating speed of a computer or its microprocessor, defined as the rate at which it performs internal operations and expressed in cycles per second (megahertz).

Lets define one more thing: Double Data Rate(DDR): It is an advanced version of SDRAM, a type of computer memory. DDR-SDRAM, sometimes called "SDRAM II," can transfer data twice as fast as regular SDRAM chips. This is because DDR memory can send and receive signals twice per clock cycle.

With that out of the way, lets start at PC1-#### and work our way up to PC3-#### and the example up there to break down how these numbers work.

DDR
This nice, slow RAM has a 100MHz Memory Clock speed, meaning it can process 200 Million operations per second. Remember, since we're talking about DDR-SDRAM, the data rate is doubled (essentially 100 MHz * 2). Though it has a clock speed of 100 MHz, for marketing purposes, this will be marketed at 200 MHz (or DDR-200), it's effective clock based on its "Double Data Rate".

Now, the Module Name (PC-####) is based on transfer rate and is actually the PC sped rating. You're going to multiply the effective clock speed by 8, the width (in Bytes) of all DDR SDRAM sticks. In the example above, you'd be taking the 200 * 8 = 1600. Slap a PC in front of that and you have PC1600.

Why is 8 the multiplyer you ask? Modern DRAM is 64 "bits" wide. Bit's are usually convered into Bytes and since there are 8 bits in a Byte, divide 64 by 8 and you get 8. The 64-bit width converts into 8-bytes (your multiplier).

DDR 2

When we're talking about DDR 2, it's twice as fast as DDR as it clock doubles the I/O circuits on the chips, speeding up the input/output and adding special buffers.

So that same 100 MHz clock speed translates into (100 MHz * 2) 2 = 400 MHz (or DDR2-400). Multiply that by 8 and (and slap a PC2 in front) you have PC2-3200.

DDR3

DDR3 doubles the buffer of DDR2 from 4-bits to 8-buts, giving it a bandwidth boost. There are also some other features thrown in there that I wont get into.

So that same 100 MHz clock speed translates into ((100 MHz * 2) 2)2 = 800 MHz (or DDR3-800). Multiply that by 8 and (and slap a PC3 in front) you have PC3-6400.

That should give you a basic understanding of how these numbers work. The bottom line doesn't seem to matter to me as I'm always looking for the fastest my board supports (and I can afford) so the "how it works" matters little to me.

Thank you very much for this AGx, I, like you, am constantly searching for the fastest my system will allow, but the "goofy" numbering system never made much sense until I read your concise summary. I hope you are a teacher!