RAM:
RAM is extra memory that provides space for the CPU to read and write data.
Figure: RAM - DDR3
There are mainly two types of RAMs
1). SRAM - Static Random Access Memory
2). DRAM - Dynamic Random Access Memory
Differences:
Description |
SRAM |
DRAM |
| Most commonly used | No | Yes |
| Which is more Speed | Yes | No |
| Need to be refreshed | no need to refresh | Thousands of times per second |
| Expensive | Highly expensive | Less expensive |
| Supporting access time | 10 nanoseconds | 60 nanoseconds |
| Volatile type | Yes | Yes |
| Loss of content when the power is turned off | Yes | Yes |
DRAM Types:
1). SDRAM - Synchronous Dynamic Random Access Memory
2). DDR - Double Data Rate
3). Rambus DRAM - Rambus Dynamic Random Access Memory
4). DRAM - Dynamic Random Access Memory
DDR Types:
Names | Memory clock | I/O bus clock |
Transfer rate |
Theoretical bandwidth |
| DDR-200, PC-1600 | 100 MHz | 100 MHz | 0.2 GT/s | 1.6 GB/s |
| DDR2-800, PC2-6400 | 200 MHz | 400 MHz | 0.8 GT/s | 6.4 GB/s |
| DDR3-1600, PC3-12800 | 200 MHz | 800 MHz | 1.6 GT/s | 12.8 GB/s |
| DDR4-2400,PC4-19200 | 300 MHz | 1200 MHz | 2.4 GT/s | 19.2 GB/s |
| DDR4-3200, PC4-25600 | 400 MHz | 1600 MHz | 3.2 GT/s | 25.6 GB/s |
GT/s : Giga Transfer per second
MT/s : Mega Transfer per second
GB/s : Giga Bytes per second
MB/s : Mega Bytes per second
What does the MHz of RAM really mean?
we know the frequency is 1/T means how many times per second. MHz means how many times per second the RAM can communicate with the CPU.
For example, How much data in mega-/kilobytes are sent to the CPU from the RAM per second in a scenario where its being pushed to the limit.
- Compared to single data rate (SDR) SDRAM, the DDR SDRAM interface makes higher transfer rates possible by more strict control of the timing of the electrical data and clock signals.
- The interface uses double pumping (transferring data on both the rising and falling edges of the clock signal) to double data bus bandwidth without a corresponding increase in clock frequency.
- A Clock signal is produced by a clock generator.
- Clock generator will be on motherboard. Depending upon the motherboard the RAM needs to be work. If we give DDR4 on low clock cycle generator, it doesn't support.
How to know the speed of the RAM in your computer?
Open command prompt
Figure: To test the speed of RAM
Figure: Speed of RAM in MHz