Sampath Kumar

• Aug 17th, 2006

 

NVRAMNonvolatile RAM (NVRAM) is a special kind of RAM that retains data when the computer is turned off or there is a power failure. It is powered by a battery within the computer. It can also work by writing its contents to and restoring them from an EEPROM. NVRAM is typically implemented so that the chip has same amount of RAM and some non-volatile memory in it. In normal operation, all reads and writes access the RAM part of the chip. When normal operation power is lost, the chip autiomatically copies the contents of the RAM to the non-volatile memory. Then the system is again powered up, the contents of the non-volatile memory are copied back to RAM’s memory for normal system operation. PROMProgrammable Read-only memory (PROM) is an integrated non-volatile memoroy circuit that is manufactured to be empty. It can be later programmed with specific data. The programming can be done only once. After programming this data is always stored to this IC. Blank PROM chips can be bought inexpensively and coded by anyone with a special tool called a programmer. PROM chips have a grid of columns and rows just as ordinary ROMs do. The difference is that every intersection of a column and row in a PROM chip has a fuse connecting them. A charge sent through a column will pass through the fuse in a cell to a grounded row indicating a value of 1. Since all the cells have a fuse, the initial (blank) state of a PROM chip is all 1s. To change the value of a cell to 0, you use a programmer to send a specific amount of current to the cell. The higher voltage breaks the connection between the column and row by burning out the fuse. This process is known as burning the PROM.

krishnaraghava

 Profile Answers by krishnaraghava Questions by krishnaraghava

• May 22nd, 2008

 

NVRAM

1.important hardware element

2.removable chip is often located on the main system board

3.contains EEPROM

4.EEPROM  stores user -configured parameters  that have been changed or customized from the boot  PROM S  default parameters settings

5. NV RAM  contains editable and non editable areas

. non editable areas

  the ethernet address

  the system host id

.EDITABLE AREAS

. the time-of-day clock valve


6. THE CONFIGURATION DATA DESCRIBING SYSTEM OPERATING PARAMETERS


BOOT PROM

1.  each system has a boot prom chip

2. 1mbyte chip is typically located on the same board as the cpu