Verdict: Meet the world's first heatpipe-cooles PSU
Zalman is one of the most innovative companies in the IT industry, with an enviable track record, including highlights such as the Reserator water-cooling kit and the TNN 500 AF chassis. The ZM600-HP is also innovative, as it's the first PSU to be cooled by not only a HSF, but also by a heatpipe. Heatpipes have done wonders for CPU HSF performance, so obviously, Zalman is hoping that the same will be true for the ZM600-HP.
As with many good 600W PSUs, the ZM600-HP distributes its power evenly across four 12V rails, each rated to supply up to 16A, or a maximum combined output of 504W. As a result, the 3.3V and 5V rails are rated at 24A, which is less meaty than in other 600W PSUs. The power distribution of the ZM600-HP is rather unusual, and is as follows: 12V1 supplies CPU1 and CPU2, 12V2 the second PCI-E plug and also CPU1 and CPU2 if you use a different set of cables, 12V3 the motherboard, S-ATA and Molex ports, and 12V4 the primary PCI-E plug.
The ZM600-HP failed to deliver sufficient voltage on its 5V rail when we tried to draw 24A from it, as the output of this rail dropped to 4.54V - well short of the 4.75V required by the ATX spec. The ZM600-HP isn't particularly efficient either, averaging just 75 per cent at 100 per cent load. As with all PSUs, the ZM600-HP is less efficient at lower load levels, but at 50 per cent load its efficiency dropped to a mere 59 per cent, which is well short of the 65 per cent requirement of the ATX spec.
CONCLUSION
The ZM600-HP runs very cool and quietly, no doubt thanks to its heatpipe cooling system, but it's very inefficient and has a weak 5V rail. Given the large number of 600W PSUs on the market today, it's more of a curiosity than a must-buy.
