Dual-ported RAM

Dual-ported RAM is a type of Random Access Memory that allows multiple reads or writes to occur at the same time, or nearly the same time, unlike single-ported RAM which only allows one access at a time.

Video RAM or VRAM is a common form of dual-ported dynamic RAM

Dynamic random access memory

Dynamic random-access memory is a type of random-access memory that stores each bit of data in a separate capacitor within an integrated circuit. The capacitor can be either charged or discharged; these two states are taken to represent the two values of a bit, conventionally called 0 and 1...

 mostly used for video memory, allowing the CPU

Central processing unit

The central processing unit is the portion of a computer system that carries out the instructions of a computer program, to perform the basic arithmetical, logical, and input/output operations of the system. The CPU plays a role somewhat analogous to the brain in the computer. The term has been in...

 to draw the image at the same time the video hardware is reading it out to the screen.

Apart from VRAM, most other types of dual-ported RAM are based on static RAM

Static random access memory

Static random-access memory is a type of semiconductor memory where the word static indicates that, unlike dynamic RAM , it does not need to be periodically refreshed, as SRAM uses bistable latching circuitry to store each bit...

 technology.

Most CPUs implement the processor register

Processor register

In computer architecture, a processor register is a small amount of storage available as part of a CPU or other digital processor. Such registers are addressed by mechanisms other than main memory and can be accessed more quickly...

s as a small dual-ported or multi-ported RAM (see Register File

Register file

A register file is an array of processor registers in a central processing unit . Modern integrated circuit-based register files are usually implemented by way of fast static RAMs with multiple ports...

).