Memory is selected for the system depending on its motherboard configuration. The motherboard should support different characteristics of the memory. The different memory characteristics are:
A. Size of a Data Bus of Memory
B. Module Error Checking and Correcting Module
C. Parity and Non-Parity chips
D. Memory Frequency
E. Memory Bank
Size of the Data Bus of a Memory Module
Size of the data bus specifies the amount of information flowing in each clock cycle. The data bus size differs depending on the memory modules. A single sided memory module will have a different data bus size from a double-sided memory module.
A 30-pin single sided memory module will have an 8-bit data bus whereas a 72-pin single sided memory module will have a 32-bit data bus. A 72-pin double-sided memory module will have 64-bit data bus.
Before installing SIMM on the motherboard, check the type and the capacity of the DRAM chip.
Error checking and Correcting Module
Error checking and correcting modules detects single-bit and multiple-bit errors. The memory bus uses this module for detecting and correcting errors of the memory block. A BIOS program is set in the ECC module. This program uses the parity-checking program for checking the accuracy of the data transmission from the memory to the processor. The memory chips group the parity bits into 7-bit block of memory for an ECC module. For example, to protect 32 BITS of data, an ECC module uses 7 bits of memory block.
Parity and Non-Parity
When the data is transferred from the CPU to the memory, different types of error may occur. The parity-checking module detects these errors. This module only detects and notifies the user about the error. The error is corrected using the ECC (Error Correction Coding) module. A SIMM module of 3 bit, 6 bit, 9 bit, 12 bits, 18 bits, or 36 bits chips may either have the parity-checking or the non-parity checking modules with it. The recent Pentium processors do not have parity chips. This is because the memories of the recent processors are generally error free. To determine the parity checking module in 30 and 72 pin SIMMS, then count the number of DRAM chips in the module. An odd number indicates a parity chip and an even number indicates a non-parity chip.
Front Side Bus (FSB) is used to describe the Data Bus. CPU frequency is set as a multiple of FSB. For example, a CPU of 500MHz may have a FSB of 100MHz. This means that the CPU is set to run 5 times the FSB.
The FSB and Memory must work at the same frequency. To increase the FSB frequency, the Memory frequency has to be increased.
You may also be interested in