How many types of RAM are there?

Answer 1

Dynamic Random Access Memory(DRAM):-

• contents are constantly refreshed 100times per second.

• Access time 60-70 nanoseconds.

Synchronous dynamic random access memory(SDRAM):-

• quicker than DRAM

• access time than 60 nanoseconds.

Direct rambus Dynamic Random Access Memory(DRDRAM):-

• new type of ram architecture.

• access time is 20 times faster than DRAM.

• more expensive.

Static random access memory(SRAM):-

• doesn't need refreshing.

• retains contents as long as power applied to the chip.

• access time is around 10 nanoseconds.

• used for cache memory, CPU registers.

• CMOS SRAM also data and time settings, powered by small battery.

Cache memory:-

• small amount of memory typically 256 kilobytes to 32 megabytes (depending on computer).

• temporary storage for often used instructions and data

• cpu checks to see whether the next instructions it requires in cache.

• if not the cpu has to fetch next information from the main memory.
• Often implemented in multiple levels: L1I/L1D, L2, L3, etc.

Video random access memory:-

• holds the data that can be displayed on the computer.

• Has two data paths allowing to READ & WRITE to occur at same time

• a graphics card may have its own VRAM chip on board.

Flash Memory:-

• contents are retained even without power
• read cycles are similar to SRAM
• unfortunately write cycles are about 100 times slower than read cycles
• due to this read/write timing asymmetry, these are more commonly used as "solid state disks" like Compact Flash, SD cards, "USB pen drives", etc. than as normal computer memory

Nonvolatile Random Access Memory(NOVRAM):-

• contents are retained even without power
• implemented as and SRAM with Flash Memory backup storage
• at power on, internal circuits copy the Flash Memory to the SRAM all bits at the same time in one cycle
• while power is on the SRAM is accessed as normal
• when a signal is received from the powersupply warning that power is turning off, internal circuits copy the SRAM to the Flash Memory all bits at the same time, however as the Flash Memory write time is much longer than its read time this powersupply warning signal must significantly precede actual loss of power at the NOVRAM chip.

Ferrite magnetic core memory:

• contents are retained even without power
• has been considered obsolete since about 1980
• even with automated machine assembly these still required significant hand labor to build

Ferromagnetic Random Access Memory(FRAM):-

• contents are retained even without power
• Integrated circuits intended to replace DRAM are still in development