RAM stands for Random Access Memory.
RAM is where all of the transactions are taking place. When you use a program, the program itself and all the data associated with it are moved off of the hard drive and are put into RAM, so that calculations can be performed on that data. The information is then stored back onto the hard drive. The CPU can’t just directly use data from the hard drive because the hard drive is too slow for the CPU. RAM is faster, but still not quite as fast as the CPU. However, RAM is more expensive than hard drives.
RAM is one of the most important components of your computer. The faster RAM you have, the faster your computer will perform.
Different motherboards may have different types of slots for RAM.
RAM types
- Use System Information to verify RAM install
- Can use the Windows Memory Diagnostics program to verify RAM functionality
SODIMM
DIMM stands for Dual In-line Memory Module. It’s called dual because it has a set of contacts on each side of the memory card. The contacts are different on each side of the memory module.
SODIMM stands for Small Outline Dual In-line Memory Module. It’s about half the width of the DIMM. You will find SODIMMS in many laptops or mobile devices.
SODIMM can found in DDR2, DDR3, and DDR4 SDRAM
DDR2
- DDR2 uses 240 pins and has one notch similar to the previous DDR. But the notch is offset.
- DDR2 stands for Double Data Rate 2.
- The DDR2 speed is essentially 4 times the speed of the motherboard system clock. For example if the Core RAM Clock speed is 100MHz then DDR2 speed would be DDR2-400. The PC Speed Rating would then be the DDR2 speed multiplied by 8. So in the previous example, the PC Speed Rating would be PC2-3200.
- DDR is type of SDRAM. SDRAM is the type of RAM on a DIMM?
- Doubles speed of DDR.
- DDR2 is not backward or forward compatible. You can’t put a DDR2 module in a DDR or DDR3 slot.
- DDR2 DIMM only requires 1.8V of power compared to 2.5V that was needed for DDR1.
DDR3
- DDR3 also uses a 240 pin stick with a notch that is offset from DDR2.
- DDR quadruples the speed of DDR. It is twice the data rate of DDR2. And is 8 times the speed of the motherboard system clock. For example, if the Core RAM Clock speed is 100 MHz, DDR3 Speed rating would be DDR3-800 and the PC Speed rating would be PC3-6400. The PC speed rating is in bits whereas the DDR3 speed rating is in bytes so the PC3 speed rating is always 8 times the DDR3 speed.
- Maximum capacity was increased to 16 GB per DIMM
- Not compatible with DDR2 slot. Requires less power.
- XMP to allow for overclocking
- Triple channel architecture
DDR4
- DDR4 uses a 288 pin stick with 1 notch offset from DDR3, DDR2, DDR.
- DDR4 provides a speed increase over DDR3.
- Increases the maximum size to 64 GB per DIMM.
- Not backward compatible.
- Whereas DDR3, DDR2, DDR speed ratings were based on the clicks of the clock, DDR4 is measured by the bandwidth, how many megetransfers per second (the actual amount of data that’s being moved).
Single channel
Single Channel RAM doesn’t utilize multiple channels between the RAM and memory controller to increase the transfer speed between the two components.
Dual channel
To improve RAM performance, some motherboards use a dual channel architecture. With dual channel, DIMMs must be installed in matched pairs in the motherboard slots with matching colors. For example, there might be two blue slots and two black slots. Dual channel is a feature of the motherboard, and not the RAM itself. Ordinary RAM can be used in dual channel slots. In dual channel, the system alternates between reading two physically separate memory modules, allowing it to read and write data twice as fast.
With dual channel memory, you’ll need to use pairs of memory modules. Exact matches are best. You don’t want to use different sizes or different performance specifications.
If your motherboard has dual channels and you only insert one RAM stick, the computer may not even boot. Otherwise, you’ll see an error on startup saying that the computer is running in single channel mode. You also need to make sure you insert the RAM into the correct slots on the motherboard. You may have 4 RAM slots that are dual channel. Channel A is two certain slots and Channel B are the remaining slots. If you only have 2 RAM sticks, make sure you put them in the two slots designated for Channel A (versus a slot from Channel A and a slot from Channel B).
Dual channel allows you to talk to both sticks of RAM at once, which makes things faster.
Triple channel
With triple channel you’ll need to use 3 RAM modules with identical speed and capacity.
Error correcting
- Error Correction Code (ECC) RAM detects if a single bit is incorrect and fixes these errors on the fly. But it’s slower, more expensive, and requires special motherboards (usually servers)
- Error correcting is used on critical computer systems such as VM servers, database servers, and basically any server.
- ECC ads an extra bit per byte to RAM.
Parity vs. non-parity
- Parity does error checking that uses the MCC to check parity bits to identify incorrect data. Replaced by ECC RAM.
- Parity memory adds an additional parity bit to the memory that’s normally transferred across the memory modules. It can detect when an error has occurred but it has no way to correct the error.
- RAM modules with parity or ECC will have an extra chip on them.
- In odd parity, a parity bit is used to make sure the total number of ones in an 8 bit byte of data is an odd number. For example, if you had 11010010, there are four 1’s. Therefore, the 9th parity bit would be a 1 so that there would be an odd number of 1’s: 110100101.
- In even parity, a parity bit ensure the total number of 1’s is an even number. For example, if you had 11001011, there are five 1’s so the parity bit would be 1 so that there are an even number (6) ones: 110010111.
- Parity is not failure proof, but it is quick and doesn’t impede memory access time like error checking routines would.
- A DIMM is 64 bits wide. With parity checking the DIMM would have 8 extra bits (1 parity bit for every 8 bit byte). Therefore, a DIMM with parity is 64+8=72 bits wide. If your system supports parity then you must use parity memory modules.
To see how parity checks work, view this Professor Messer video:
RAM Installation
Watch the below video on how to install RAM.
