What is REM?

Where is REM Used?

How often does a memory error happen?

 REM (reliable memory) line of SIMMs from DIVO Systems, Inc. is a collection of error correction memory modules compatible with industry standard SIMMs. By adding additional memory chips and employing a proprietary ECC logic on the SIMM, DIVO Systems, Inc. provides an easy upgrade for any computer system that requires reliable memory.

 This product can be used in mission critical applications where the computer or an embedded system should never fail. These systems are usually protected in some of their components: redundant disks, multiple power supplies, parallel CPUs. However nothing special is ever done for the memory. Since memory is not an active component, it can not hang the system because of a malfunction. But when memory cells are corrupted, software will frequently halt the system.

 Applications that require absolute trustworthiness of computation results need reliable memory. For example: stress analysis packages, financial software, etc. Since both the program and data are kept in memory, neither can be trusted.

 According to research made by Hewlett-Packard (Hewlett-Packard Journal, February 1996, pp. 44-51) single bit error on large 2 GBytes memory system is expected to occur once every 868 hours or ten times per year. On some PCs with just 32 Mbytes of memory the error rate will be much lower, but still significant.

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REM specifics:

•Workstations: Typically workstations correct single bit errors by logic on the board.

•PCs: Some of the latest PC motherboards have error correction capabilities. They correct a single bit error in a 64-bit word.

•Superior protection. For example REM-V6 corrects up to 12 bits in a 36-bit word! Also it allows up to four memory chips to fail completely without any affect on the SIMM’s behavior.

•Protection logic resides on the SIMM itself that makes it compatible with the regular PC memory and can be used in any existing memory slot. No custom adapters, special motherboards or time consuming installations required. It is just plugged in as any regular memory SIMM.

•Different levels of protection and various custom error correction schemes are possible.