Internal & Cache Memory

Hello ..how are you doing? . I just wanna share with all you about memory. This time we will look further on  internal and cache memory.

what is internal memory??

Primary storage (or main memory or internal memory), often referred to simply as memory, is the only one directly accessible to the CPU. The CPU continuously reads instructions stored there and executes them as required. Any data actively operated on is also stored there in uniform manner.

what is cache memory??

Cache is generally divided into several types, such as L1 cache, L2 cache and L3 cache. Cache built into the CPU itself is referred to as Level 1 (L1) cache. Cache is in a separate chip next to the CPU is called Level 2 (L2) cache. Some CPUs have both, L1 and L2 cache built-in and assign a separate chip as cache Level 3 (L3) cache. Cache built in CPU faster than separate cache. However, a separate cache is still about twice as fast from Random Access Memory (RAM). Cache is more expensive than RAM, but the motherboard with built-in cache very well in order to maximize system performance.

The advantage of cache:

Cache serves as a temporary storage for data or instructions needed by the processor. In addition, the cache function to speed up data access on the computer because the cache stores data / information has been accessed by a buffer, to ease the work processor.

Another benefit of cache memory is that the CPU does not have to use the bus system motherboard for data transfer. Each time the data must pass through the system bus, the data transfer rate slow the ability motherboard. CPU can process data much faster by avoiding obstacles created by the system bus..

In computing, memory refers to the physical devices used to store programs (sequences of instructions) or data (e.g. program state information) on a temporary or permanent basis for use in a computer or other digital electronic device. The term primary memory is used for the information in physical systems which function at high-speed (RAM), as a distinction from secondary memory, which are physical devices for program and data storage which are slow to access but offer higher memory capacity. Primary memory stored on secondary memory is called "virtual memory". Memory is a solid state digital device that provides storage for data values. It also known as memory cell that exhibit two stable states which are 1 and 0.  

Memory Hierarchy

Typical memory Refrence

}Memory Trace

◦A temporal sequence of memory references (addresses) from a real program.

}Temporal Locality

◦If an item is referenced, it will tend to be referenced again soon

}Spatial Locality

◦If an item is referenced, nearby items will tend to be referenced soon.

How Memory Cell Function?

Select Terminal	Control Terminal
To select a memory cell for a read or write operation	To indicate read/write

Volatile and Non-volatile Memory

There are two memory types: volatile and non-volatile memory. Volatile memory is memory that loses its contents when the computer or hardware device loses power. Computer RAM is a good example of a volatile memory. Non-volatile memory, sometimes abbreviated as NVRAM, is memory that keeps its contents even if the power is lost. CMOS is a good example of a non-volatile memory.

Type of Internal Memory:

ROM (Read Only Memory) 

PROM (Progammable Read-Only-Memory): 
If the content is determined by the vendor ROM, PROM sold empty and can then be filled with a program by the user. Having completed the program, fill PROM can not be removed.

EPROM (Erasable Programmable Read-Only-Memory): 
Unlike the PROM, EPROM contents can be deleted after being programmed. Elimination is done by using ultraviolet light.

EEPROM (Electrically Erasable Programmable Read-Only0Memory): 
EEPROM can store data permanently, but its contents can still be erased electrically through the program. One type EEPROM is Flash Memory. Flash Memory commonly used in digital cameras, video game consoles, and the BIOS chip.

RAM (Random Access Memory)

RAM is divided into two types, namely static and dynamic types :

Static RAM stores a bit of information in a flip-flop. Static RAM is usually used for applications that do not require large capacity RAM memory. 

Dynamic RAM data store one bit of information as a payload. Dynamic RAM using a substrate capacitance gate MOS transistors as memory cells shut. To keep dynamic RAM stored data remains intact, the data should be refreshed again by reading and re-write the data into memory. Dynamic RAM is used for applications that require large RAM capacity, for example in a personal computer (PC)

SRAM (Static Random Access Memory)

 is a type of RAM (a type of semiconductor memory) that do not use a capacitor. This resulted in SRAM does not need periodic refresh like the case with DRAM. This will in turn create a higher speed than DRAM. Based on the functions split into Asynchronous and Synchronous.

EDORAM (Extended Data Out Random Accses Memory)

 is a type of RAM that can store and retrieve the contents of memory at once, so he wrote was read speed becomes faster. Generally used in lieu of the previous PC Fast Page Memory (MTF) of RAM. Like FB DRAM, EDO RAM has a maximum speed of 50MHz EDO RAM should also be significant L2 Cache takes to make everything goes quickly, but if the user does not have it, then EDO RAM will run much slower.

SDRAM (Synchronous Dynamic Random Acces Memory). 

SDRAM is not an extension of a long series EDO RAM, but a new type of DRAM. SDRAM starts running with 66MHz transfer rate, while the page mode DRAM and EDO longer be running at a maximum of 50MHz. To accelerate the performance of the processor, the new generation of RAM such as DDR and RDRAM are usually able to support better performance.

DDR (Double Data Rate SDRAM). 

Double date rate synchronous dynamic RAM is just like SDRAM except that it has higher bandwith (greater speed). Maximum transfer rate to L2 cache is approximately 1064 MBps (for DDR SDRAM 133 MHZ)

Direct Mapped Cache

If the cache contains 2^k bytes, then the k least significant bits (LSBs) are used as the index.– data from address i would be stored in block i mod 2^k

for an example:

For example, data from memory address 11 maps to cache block 3 on the right, since 11 mod 4 = 3

and since the lowest two bits of 1011 are 11.

How big is the cache?


For a byte-addressable machine with 16-bit addresses with a cache with the following characteristics:

• ‰ It is direct-mapped (as discussed last time)
• ‰ Each block holds one byte
• ‰ The cache index is the four least significant bits

How many blocks does the cache hold?

4-bit index -> 24= 16 blocks

How many bits of storage are required to build the cache (e.g., for the 
data array, tags, etc.)?
tag size = 12 bits (16 bit address - 4 bit index) (12 tag bits + 1 valid bit + 8 data bits) 
x 16 blocks = 21 bits x 16 = 336 bits

So short, and yet so meaningful, right? That's all for memory.Hopefully that this topic can help all of you know more about memory..Till we meet again...Have a great day lovelies! 

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