RAM - Random-Access memory

RAM (Random Access Memory) or RWM (Read Write Memory) is the memory in which a computer places data during processing. The characteristics of this memory are:
- its access speed, this speed is essential to quickly provide the data to the processor.
- its volatility, this volatility implies that the data are lost as soon as the computer stops being supplied with electricity.
There are several types of RAM:
SDRAM or Synchronous Dynamic Random Access Memory is a particular type of RAM that has had a long career since it was used from Pentium to Pentium 4. It replaced RAM EDO in the heart of our computers .
the SDRAM synchronizes with that of the motherboard. Reading the data in synchronization with the bus of the motherboard makes it possible to avoid certain waiting times, and in particular that due to synchronization with the motherboard. The waiting cycle is thus reduced. The SDRAM can thus operate with a rate of up to 200 MHz and reduce its access time to 5 ns. In a PC, it comes in barrel with 168 pins in 64 bits and two notches.

RDRAM (Rambus Dynamic Random Access Memory) is a RAM technology developed by the company Rambus. It had a strong publicity around 2000 and during the release of the first Intel Pentium IV processors. This type of memory being very expensive, Intel abandoned it quickly in favor of the DDR SDRAM.

DDR SDRAM or Double Data Rate Synchronous Dynamic Random Access Memory is a type of integrated circuit memory used in computers since 2003 and commonly abbreviated as DDR. DDR provides better bandwidth than ordinary SDRAM by transferring data on both the rising edge and the falling edge of clock pulses, doubling the memory access speed, in reading and writing. This feature gives it its name: "Double Data Rate" (compared to the SDR SDRAM).
Thus, a motherboard with DDR-SDRAM memory and having a memory bus clocked at 133 MHz is equivalent in data rate to 266 MHz SDRAM.

DDR2 SDRAM or DDR2 is the second generation of DDR-based RAM for personal computers, the first being DDR technology. This type of computer memory uses integrated circuits. This technology is part of the SDRAM family of flash memories, which itself is one of the many versions of DRAMs. The major difference between DDR and DDR2 is that the bus frequency is now twice that of the memory cell group. Four data words can thus be transferred per cycle of the memory cells. At equal memory cell frequency, the DDR2 has a bit rate twice that of the DDR. The clock frequency of the DDR2 memory is also generally greater due to technical improvements at the electrical interface, with built-in connections, a prefetch buffer, and output circuits external to the chip.