Verdict: None of the Xeon 5100-series is worth buying now.

The Xeon 5100-series of desktop CPUs were the first to use the Core architecture and marked the beginning of Intel's return to the top of the processor market.

Internally, a Xeon 5100-series CPU is almost identical to a Core 2 Duo, with each CPU having two processing cores that share a large 4MB Level 2 cache. Each core has its own 32KB of Level 1 cache, and all the usual Intel processor features are supported, including 64-bit instructions, SpeedStep, Execute Disable and SSE3. Curiously, the two entry-level models of the Xeon 5100-series have a lower effective FSB than the other models - 1,066MHz as opposed to 1,333MHz. However, you won't need to upgrade your motherboard if you're upgrading from one model to another, as all the 5000-series core logic chipsets support both FSB frequencies.

With two Xeon 5100-series CPUs running together in parallel, you'd expect awesome performance but, since the series was first introduced, Intel has launched an entire range of quad-core CPUs (many of which are dual-processor and quad-processor capable). As such, a pair of Xeon 5160s will no longer provide you with the fastest PC in the world, as it's easily outclassed by a pair of Xeon 5300-series CPUs (see below) or Xeon 5400-series CPUs (see p89). As for desktop applications, you're better off buying a far cheaper Core 2 Quad than two Xeon 5100-series CPUs.

That said, if you own a pair of Xeon 5100-series CPUs, don't despair - the higher-spec models are still great at tasks such as video encoding and Folding@home. However, if you find your Xeon 5100-series CPU a little on the slow side, you can upgrade to a pair of Xeon 5300-series CPUs or low-end Xeon 5400-series CPUs without changing the motherboard and RAM.

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