Virtual Channel Random Access Memory (VC-RAM in short, other names such as VC-SDRAM, VCSDRAM, VCDRAM, or VCM) is a proprietary type of SDRAM that was produced by NEC, but released as an open standard with no licensing fees. VCM creates a state in which the various system processes can be assigned their own virtual channel, thus increasing the overall system efficiency by avoiding the need to have processes share buffer space. This is accomplished by creating different "blocks" of memory, allowing each individual memory block to interface separately with the memory controller and have its own buffer space. The only motherboards ever able to support VC-RAM were for AMD Athlon and Intel Pentium 3 processors. A VC-RAM module is physically similar to a SDR SDRAM memory module, so VC-RAM capable motherboards are also able to use standard SDR SDRAM, but they cannot be mixed together.
VC-RAM has higher performance than SDRAM because it has significantly lower latencies. The technology was a potential competitor of Rambus or RDRAM because VC-RAM was not nearly as expensive as RDRAM was; however, the technology did not catch on. Instead, NEC accepted dual data rate (DDR) SDRAM as the successor of SDR SDRAM. [1]
NEC claims 3% boost in Quake benchmarks with 20% increase in system performance.[citation needed]
