Chips and modules
For use in Desktop computers, DDR, DDR2, DDR3 SDRAM is supplied in DIMMs (Dual Inline Memory Modules) with 240 pins and a single locating notch
Laptop DDR, DDR2, DDR3 SO-DIMMs, sometimes written without the dash: SODIMM, have 200 pins and often come identified by an additional S in their designation. The “SO” in SODIMM stands for “Small Outline”.
DIMMs are identified by their peak transfer capacity (often called bandwidth).
| Standard name | Memory clock(MHz) = 1/cycle |
Cycle time(ns) = 1/clock | Data rate(MT/s) = 2x clock | Module name= rounded transfer rate | Peak transfer rate(MB/s) = 8x Data Rate (8byes per Transfer) = 16x clock | Timings[2][3](CL-tRCD-tRP) | CAS latency(ns) = Timings * 1/2 * cycle |
|---|---|---|---|---|---|---|---|
| DDR | |||||||
| DDR-200 | 100 | 10 | 200 | PC-1600 | 1600 | ||
| DDR-266 | 133⅓ | 7.5 | 266⅔ | PC-2100 | 2133⅓ | 2.5-3-3 | 18.75 |
| DDR-333 | 166⅔ | 6 | 333⅓ | PC-2700 | 2666⅔ | ||
| DDR-400A DDR-400B DDR-400C |
200 | 5 | 400 | PC-3200 | 3200 | 2.5-3-3 3-3-3 3-4-4 |
12.5 15 15 |
| Standard name | Memory clock(MHz) = 1/cycle |
Cycle time(ns) = 1/clock | Data rate(MT/s) = 4x clock | Module name= rounded transfer rate | Peak transfer rate(MB/s) = 8x Data Rate (8byes per Transfer) = 32x clock | Timings (CL-tRCD-tRP) | CAS latency(ns) = Timings * 1/2 * cycle |
| DDR2 | |||||||
| DDR2-400B DDR2-400C |
100 | 10 | 400 | PC2-3200 | 3200 | 3-3-3 4-4-4 |
15 20 |
| DDR2-533B DDR2-533C |
133⅓ | 7⅓ | 533⅓ | PC2-4200* | 4266⅔ | 3-3-3 4-4-4 |
11¼ 15 |
| DDR2-667C DDR2-667D |
166⅔ | 6 | 666⅔ | PC2-5300* | 5333⅓ | 4-4-4 5-5-5 |
12 15 |
| DDR2-800C DDR2-800D DDR2-800E |
200 | 5 | 800 | PC2-6400 | 6400 | 4-4-4 5-5-5 6-6-6 |
10 12½ 15 |
| DDR2-1066E DDR2-1066F |
266⅔ | 3¾ | 1066⅔ | PC2-8500* | 8533⅓ | 6-6-6 7-7-7 |
11¼ 13⅛ |
| Standard name | Memory clock (MHz) |
Cycle time (ns) |
Data rate (MT/s) = 8x clock |
Module name | Peak transfer rate (MB/s) = 8x Data Rate (8byes per Transfer) = 64x clock |
Timings (CL-tRCD-tRP) |
CAS latency (ns) |
| DDR3 | |||||||
| DDR3-800D
DDR3-800E |
100 | 10 | 800 | PC3-6400 | 6400 | 5-5-5
6-6-6 |
12 1⁄2
15 |
| DDR3-1066E
DDR3-1066F DDR3-1066G |
133⅓ | 7 1⁄2 | 1066⅔ | PC3-8500 | 8533⅓ | 6-6-6
7-7-7 8-8-8 |
11 1⁄4
13 1⁄8 15 |
| DDR3-1333F*
DDR3-1333G DDR3-1333H DDR3-1333J* |
166⅔ | 6 | 1333⅓ | PC3-10600 | 10666⅔ | 7-7-7
8-8-8 9-9-9 10-10-10 |
10 1⁄2
12 13 1⁄2 15 |
| DDR3-1600G*
DDR3-1600H DDR3-1600J DDR3-1600K |
200 | 5 | 1600 | PC3-12800 | 12800 | 8-8-8
9-9-9 10-10-10 11-11-11 |
10
11 1⁄4 12 1⁄2 13 3⁄4 |
| DDR3-1866J*
DDR3-1866K DDR3-1866L DDR3-1866M* |
233⅓ | 4 2⁄7 | 1866⅔ | PC3-14900 | 14933⅓ | 10-10-10
11-11-11 12-12-12 13-13-13 |
10 5⁄7
11 11⁄14 12 6⁄7 13 13⁄14 |
| DDR3-2133K*
DDR3-2133L DDR3-2133M DDR3-2133N* |
266⅔ | 3 3⁄4 | 2133⅓ | PC3-17000 | 17066⅔ | 11-11-11
12-12-12 13-13-13 14-14-14 |
10 5⁄16
11 1⁄4 12 3⁄16 13 1⁄8 |
* Some manufacturers label their DDR2 modules as PC2-4300, PC2-5400 or PC2-8600 instead of the respective names suggested by JEDEC. At least one manufacturer has reported this reflects successful testing at a higher-than standard data rate[4] whilst others simply round up for the name.
Note: DDR2-xxx denotes data transfer rate, and describes raw DDR chips, whereas PC2-xxxx denotes theoretical bandwidth (with the last two digits truncated), and is used to describe assembled DIMMs. Bandwidth is calculated by taking transfers per second and multiplying by eight. This is because DDR2 memory modules transfer data on a bus that is 64 data bits wide, and since a byte comprises 8 bits, this equates to 8 bytes of data per transfer.
To clarify 2 similar acronyms:
SRAM – Static RAM – this type of memory is used in various places in various chips in the PC (but not main memory, nor hard drisk drive main storage). It is used in caches and register files.
SDRAM – Synchronous Dynamic RAM – this is the type of memory people mean when they say “my pc has 4GB of memory” (4GB is typical in 2013).
Even tho they both start with ‘S’ one is Static and the other is not. In one case the ‘S’ means “Static” and in the other it means “Synchronous”.
Another memory term:
SODIMM – Small Outline DIMM. Ie laptop memory.
Also begins with ‘S’ but in this case the ‘S’ means “Small”.
2 other terms:
“Volatile” means memory that is lost when power is applied. Examples are the memory (not the hard disk drive) inside your computer.)
“Non-Volatile” means memory is still store when power is turned off. Examples are flash, as in usb drives. Eg usb drive retains its storage when unplugged.)
Reference: Random-access memory on Wikipedia