Internal memory
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A computer uses a hierarchy of internal and external memory systems. Internal memory includes RAM, ROM, and cache, which provide fast access but are more expensive per byte. RAM allows independent access to each memory location and is used for main memory. ROM permanently stores data and is used for boot programs. Cached memory uses SRAM for faster access than RAM. External memory includes hard disks and USB drives, which provide large, inexpensive storage but are much slower to access.
![EPROM
Eraser
contd.,
requires breakup the charges trapped
in the transistors of memory cell.[this is
done by break the chip to ultraviolet light].
This reason EPROM packaged with
transparent window.
Disadvantages:
Entire EPROM is erased as a whole and
selective erasing is not possible.
Should be removed from the chip for
reprogramming.](https://image.slidesharecdn.com/internalmemory-140108003818-phpapp02/85/Internal-memory-18-320.jpg)
Internal memory
- 2. Introduction Computer memory exhibits different types of technique, organization, performance, size and cost. But, no technology is optimal in memory requirements for a computer system. As a result, a computer equipped with a hierarchy of memory subsystems. Some are internal to the system – RAM, ROM, CACHE External memories are Hard disk, Optical and Pen drive etc.,
- 3. RAM Storage cell unit consists of N cells each of which can store 1 bit either 0 or 1. Every location of RAM accessed independently. So, the access and cycle times can constant. The address of memory location transferred through MAR using address bus. The address then proceed by the address decoder. Which select required location in storage unit.
- 4. RAM The contd., contents of the selected location placed in IR through MDR processor register. The R/W control line specifies the type of access to be performed. Write operation, the word to be place in MDR and the address specified in MAR and then transferred to selected cell. DDR RAM-Double Data Rate synchronous dynamic random access memory
- 5. RAM
- 7. ROM Data are written into a ROM when it is manufactured. ROM is mask programmed by the manufacturer in the factory with the contents ordered by the customers. The contents are fixed by metal masks used during chip fabrication. Once programmed, the contents cannot be erased. Even a single bit wrongly programmed the ROM chip is useless.
- 8. Application Used to store control programs such as micro program. Character generation, code conversion, etc.,
- 10. Boot screen
- 13. PROM-Programmable ROM PROM is a field programmable device. The customer buy a blank PROM and store desired data using PROM programmer(burner). Programmability achieved by inserting a fuse at point P. Before programmed, the memory contains all 0s. The user can insert 1 by burning out the fuse in the particular cell using high current pulse. The PROM chip can be programmed only once and its contents cannot be erased. PROM are flexible , faster and less expensive because they can be programmed directly by the user.
- 14. Application-PROM Boot program in micro computer
- 15. PROM
- 16. PROM
- 17. EPROM-Erase programmable ROM A rewritable chip that holds its contents without power. Previous data can be erased and new data can be inserted EPROM chips are written on an external programming device before being placed on the circuit board. Capable of retaining stored information for a long time.
- 18. EPROM Eraser contd., requires breakup the charges trapped in the transistors of memory cell.[this is done by break the chip to ultraviolet light]. This reason EPROM packaged with transparent window. Disadvantages: Entire EPROM is erased as a whole and selective erasing is not possible. Should be removed from the chip for reprogramming.
- 19. EPROM
- 21. EEPROM-Electrically Erased PROM It can be both programmed and erased electrically( flashed back to Zero). They do not need to removed when the chip content erasure. Also, erase selected content in the chip. Erasing and programming dynamically without removing the EEPROM from the circuit. Disadvantages: Different voltages are required for erasing, reading and writing the data.
- 22. Application Used as ROM Critical system setup information in a nonvolatile way.
- 23. EEPROM
- 24. EEPROM
- 25. EEPROM
- 26. Flash Memory Recent kind of EEPROM is flash memory. Which is erased by ultraviolet light. EEPROM is byte erasable whereas, flash memory is a block erasable. Like a EEPROM when erasing the contents of flash memory no need to remove from the circuit. In flash it is possible to read the contents of a single cell, but is only possible to write an entire block of cells.
- 27. Flash memory It contd., need single power supply and consume less power. Application: Cell phones, hand held devices, digital camera, washing machine, AC, Tablet etc. NOTE: low power consumption of flash memory makes it attractive for use in portable equipment that is battery driven
- 28. Flash Card Mount flash chips on a small card. That card simply plugged into a slot. 64 MB can store 1 hour songs. Now a days, the device can equipped with up to 32GB flash memory.
- 32. Speed, size and Cost SRAM chip is very fast memory in the computer system. but it is expensive because their basic cells have 6 transistors. Which impossible to packaging a very large number of cells onto a single chip. Cost wise also expensive. Cache memory can be implemented based on SRAM. Alternative is to use DRAM, which can have same basic cells and thus much less expensive. But significantly slower. Still it is small in size compared to magnetic drives.
- 33. Speed, size and Cost Main memory can be build with DRAM. Secondary storage- large memory space with reasonable price but much slower than semiconductor memory unit.
- 34. conclusion Huge amount of cost-effective storage can be provided by magnetic disk. Main memory can be built with DRAM. SRAM to be used in smaller unit where speed is of the essence.(Cache)
- 35. SPEED
- 36. SPEED Fastest access is to data held in processor registers. There are often two levels of cache, the primary cache inside processor refer to as L1. secondary cache placed outside referred as LEVEL 2(L2) usually SRAM chip. Next level in the hierarchy is called main memory. The typical main memory is about ten times slower than the access for the L1
- 37. SPEED The bottom level in the hierarchy is called the secondary memory such as magnetic disk. Disk provide a huge amount of inexpensive storage. But they very slow.