Tower vs rack server

A tower server is an upright, freestanding chassis that sits on a floor or desk. A rack server is a flat chassis that mounts on rails in a 19-inch equipment rack, with height counted in rack units (U). The 19-inch rack follows the EIA-310-E specification. Some towers, such as the Lenovo ThinkSystem ST650 V3, convert to a 4U rack server with a kit.

GPU count, noise and power separate them. The ST650 V3 tower takes up to four double-wide GPUs, while the 3U ThinkSystem SR675 V3 rack server takes up to eight. Lenovo declares the ST650 V3 at 37 A-weighted decibels (dBA) in its minimum configuration and 59 dBA with eight NVIDIA A2 GPUs. It declares the SR675 V3 at 68 dBA idle and 71.3 dBA operating with four NVIDIA H100 GPUs. The tower takes up to two power supplies, and its 750 W and 1,100 W options also run on 110 V. The rack server takes up to four 1,800 W to 2,600 W supplies on 220 V.

Choose a tower for up to four double-wide GPUs in an office or lab with people nearby. Choose a rack server for more than four GPUs per chassis, or for several nodes in a machine room or colocation space.

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Last verified October 7, 2026.