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Memory and Your CPU (BACK)
Today's more powerful computers include a 64-bit Pentium or PowerPC CPU. Older machines traditionally process data at 8, 16 or 32 bits. Bits refer to the maximum amount of information that can be processed by the CPU at one time. The type of memory module used in a computer is dependent on the CPU and the memory module slots. For example, powerful 64-bit machines need memory that can deliver 64 bits. This is usually accomplished by using pairs of 72-pin memory modules because each module supports 32 data bits. Alternatively, 30-pin modules support only 8 data bits and are common on less powerful machines.
30-Pin Memory Modules (BACK)
For a 32-bit CPU computer with 30-pin SIMM sockets, four 30-pin SIMMs would be needed to properly upgrade memory. Because a single 30-pin SIMM delivers 8 bits at a time, four are need to satisfy the CPU needs. The set of four makes up a bank of memory.
72-Pin Memory Modules (BACK)
A 72 pin SIMM socket supports 32-bit CPU's or better. Because 72-pin memory modules deliver 32 bits of data at a time, a 32-bit CPU would require only one module per bank, unlike the four 30-pin modules needed to accomplish the same end. In powerful 64-bit systems, pairs of 72-pin modules make up each bank of memory.
Memory Data Integrity Checking (BACK)
The memory controller installed with each computer controls the data movement to and from memory modules. In addition, the controller type determines the type of data integrity checking to perform, if any. Traditionally, computers used in more mission critical environments will include memory controllers that check for data integrity. The two most common forms of integrity checking are parity and error correction code (ECC). The increasing quality of memory components and the drive for lower memory prices has driven many personal computer manufacturers to eliminate costly data integrity checking.
Parity (BACK)
When parity data integrity is used, an extra bit is stored with every 8 bits of data in a DRAM chip. The parity data is assigned by the memory controller as it is stored and is checked as data is retrieved. If the parity data has changed, the data has lost its integrity. Determining which bit is invalid is beyond the power of parity.
Error Correction Code (BACK)
Error correction code (ECC) take parity a step further by detecting and correcting data integrity errors. A mathematical formula is used by the memory controller to reconstruct invalid data. |
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