Performance, Performance Per Dollar, Noise and Efficiency Ratings
Performance Rating
The following graph shows the PSU's total performance rating, comparing it to other units we've reviewed. To be more specific, the tested unit is shown as 100 percent, and every other product's performance is shown relative to it.
The ZM750-EBT's performance is poor; it can't even match SilverStone's ST75F-GS V2, which is based on the same platform. Compared to the rest of the competition in this category, the difference is huge (and not in a good way).
Performance Per Dollar
The following chart may be the most interesting to many of you because it depicts the unit's performance-per-dollar score. We looked up the current price of each PSU on popular online shops, using those prices and all relative performance numbers to calculate the index. If the specific unit wasn't available in the United States, we searched for it in popular European Union shops, converting the listed price to USD (without VAT). Note that all of the numbers in the following graph are normalized by the rated power of each PSU.
Thanks to its low price, the ZM750-EBT finds itself in a very good place on this chart. Personally, though, I'd rather spend a few more bucks to get a PSU with a longer hold-up time and better ripple suppression.
Noise Rating
The graph below depicts the cooling fan's average noise over the PSU's entire operating range, with an ambient temperature between 28 and 30 °C (82 to 86 °F).
This is a noisy PSU, and under tough operating conditions it will annoy most users. If you plan to build a quiet system, avoid the ZM750-EBT.
Efficiency Rating
The following graph shows the average efficiency of the PSU throughout its entire operating range, with an ambient temperature between 28 and 30 °C.
In this graph, the ZM750-EBT surpasses the performance of Corsair's RM750x and RM750i. However, those power supplies feature much better ripple performance, tighter load regulation, higher hold-up time and quieter fans. The only downside is that they cost more.
I'll need to make at least another pass through this article, but failing on +5V ripple under heavy load probably makes this a solid tier-3 unit; I'm not going to run screaming if I see one, but I wouldn't buy it either.
CONS: Ripple • Noisy under stress • Hold-up time • Inrush current • Sleeve-bearing fan • Single EPS connector • Inaccurate PWR_OK signal
Also it must also be strongly pointed out that this unit does not meet ATX specifications.
Hmmm, this one does seem a little worse than I thought at first. Any chance this particular unit had a problem? I'd think ripple could be fixed with a minor capacitor improvement, without adding too much to the price. Hopefully Zalman is paying attention.
agreed
One died days after the warranty expired and the other about a month after. I'll give Zalman credit, they made right by me by exchanging both, but it was a painful process.
While I would not recommend these current products, I can at least "tolerate" them in budget builds.
Anyway, I like your power supply reviews, Toms. You go more in-depth than any review site for power supplies (Hardwaresecrets, Johnnyguru).
Considering the same platform performs decently in the Silverstone unit, there's at least some hope that Zalman can go back, adjust a few things, and get a decent budget unit out of this.
Edit: I went back and looked at the Silverstone review. Ripple suppression was really good up to 90% load, then the 5V and 3.3V rails jumped hugely, especially the 3.3V. They did stay within ATX spec, but just barely. The 5V ripple went from 13.1mV at 90% to 40.5mV at 100%, 3.3V ripple went from 14.1mV at 90% to 49.9mV at 100%. Obviously the 3.3V ripple went out of spec at 110% load, as well as one of the crossloads, but that's a lesser sin.