Hardware caches

The first type of caches, the Hardware caches are usually memory chips that have been embedded within a device. The most common Hardware caches found in a computer system are:

• CPU cache: The L1,L2,L3 caches are used to speed-up data transfer between the processor and the main memory(i.e. RAM). The L1 and L2 caches are built right into the processor chip making them extremely fast. Whereas the newer L3 cache which also has higher capacity than L1 and L2, may be built into the motherboard as well.

• Optical drive cache: A small cache (typically 1-2 MB) is provided in all optical drives, whether CD or DVD or BD. This cache is present so that the disk burner has data available for burning, even if the CPU hits 100% utilization in some other process for a fraction of a second. The cache is also used to store data for fast access when a readable disk is first inserted into the drive.

• Hard-Disk cache: Hard-disks are the fastest permanent storage devices. They can virtually read and write data at the same time. For this purpose, a cache memory is provided in the hard drives that perform in a similar manner like the optical drive caches. The only difference is in their memory size. These may range from 8MB to 64MB.

Usually, the Hard-Disk and the Optical Disk caches are built into the hard-disk controller and the optical disk controller which are present on the hard-drives and the optical drives themselves.

Cache: Types and Functions

Cache is the memory area where a part of the most frequently (more frequently than data in the RAM) is stored.

Caches were introduced to further enhance the mismatch of various hardware components of the computer like that of the processor and peripheral devices.

The purpose of caches is simple. They enhance the speed of a computer's hardware and software parts.

Cache is of two types: Hardware and Software.

The hardware caches are usually memory chips embedded within a hardware device. The most common example of this are the L1,L2 and L3 caches of modern processors.

The software caches is the ability of the software to save the most accessed user data on the Hard-Disk or the RAM. An example of this is the internet browser cache that contains cookies, form data and partial website data.

Dynamic RAM: modules

DRAM packages are in turn often assembled into plug-in modules for easier handling. Some standard module types in order of increasing speeds are:

-DIP(Dual in-line Package) 16-pin (chip)

-SIPP(Single In-line Pin Package) (usually FPRAM)

-SIMM(Single In-line Memory Module) 30-pin (usually FPRAM)

-SIMM 72-pin (often EDO RAM)

-DIMM(Dual In-line Memory Module) 168-pin (SDRAM: Synchronous DRAM)

-DIMM 184-pin (DDR SDRAM: Double Data Rate SDRAM)

-RIMM(Rambus In-line Memory Module) 184-pin (RDRAM: Rambus DRAM)

-DIMM 240-pin (DDR2 SDRAM / DDR3 SDRAM)

Dynamic RAM: more info

Dynamic random-access memory (DRAM) is a type of random-access memory (RAM) 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.

DRAM is volatile memory, since it loses its data quickly when power is removed. The transistors and capacitors used are extremely small; hundreds of billions can fit on a single memory chip.

Dynamic random access memory is produced as integrated circuits bonded and mounted into plastic packages with metal pins for connection to control signals and buses.

Today, these DRAM packages are in turn often assembled into plug-in modules that are installed into RAM sockets in the motherboard for easier handling.

DRAM is usually arranged in a square array of one capacitor and transistor per data bit storage cell. Typically, manufacturers specify that each row must have its storage cell capacitors refreshed every 64 ms or less. Refresh logic is provided in a DRAM controller which automates the periodic refresh, so no software or other hardware has to perform it. This makes the controller's logic circuit more complicated, but this drawback is outweighed by the fact that DRAM is much cheaper per storage cell and because each storage cell is very simple, DRAM has much greater capacity per geographic area than SRAM.