SFF Roundup, Socket 939 Systems

Shuttle SN25P

SN25P Flashback

Normally, we proceed in alphabetical order. The reason we're putting the SN25P first is because we've already given it a thorough review and it is the reigning champion of socket 939. We've had more time with it, and some new developments have occurred since the initial making that it is worthwhile to take another look at the SN25P. While it originally earned our Silver Editor's Choice award, the question now is how it stands up to the new contenders.

You'll want to read the earlier review first if you haven't already, as we're not going to do a full review here. We're not including any images either, as nothing has changed other than a few BIOS screens. What we want to discuss are a few updated product launches and how they affect the SN25P. For those of you who want a condensed version, the SN25P is still a very good product and for many people, we continue to recommend it without hesitation. If you've already purchased one and you're running it, there's no real reason to be concerned as performance is very good.

Performance and Overclocking

Since our initial review, some aspects of performance have become slightly better with newer BIOS revisions. Overclocking in particular has improved quite a bit, and we can now confirm that the SN25P runs very well with all socket 939 processors up through the Venice and San Diego cores. In fact, we were able to take a Venice core up to the maximum 300 MHz bus and a 9X multiplier, which comes out as the top overclock for this group of systems. We also had a Venice 3200+ running stably at 2.7 GHz, which is a 35% CPU overclock and better than what we've reached with the same chip on desktop motherboards. Clearly, the cooling solution of the SN25P is up to the task of keeping even the fastest processors within the spec limits.

While we've said that some aspects have improved, we did notice a drop in performance in other areas. If you compare the results published in this article with those of the initial SN25P review, you will find that the scores are not the same. Some benchmarks were a bit faster, and others were a bit lower. In tweaking the BIOS for improved stability and overclocking as well as adding support for X2 processors, Shuttle may have been forced to slow other areas down a bit. Whatever the case, while the latest BIOS appears to be slightly slower, the difference is generally less than a few percent, and the additional features make the BIOS update worthwhile for most users.

Another addition to the BIOS that some people will really like: you can now set the LED brightness level for the front panel from "Off" to "100%" in increments of 12.5%. Those who dislike lights on the front of PC cases - particularly in HTPC configurations - will almost certainly approve of the change. This BIOS setting may have been present before, but it didn't work right. It does now, and the results can be seen in real time - no reboot required. It's the little things that count sometimes.

Processor Support

What about the latest cores, the Toledo and Manchester Athlon 64 X2? That's where we run into some issues. We are currently running all of the units in this roundup through additional tests, focusing on support for the Athlon X2 processors as well as the Venice and San Diego Athlon 64 parts. We'll have full details in the next few weeks, but for now, we can only state that there have been several reports of incompatibilities with the X2 chips and the currently shipping SN25P. They work for the most part, but high traffic loads on the USB2.0 ports appear to "hard" lock the system for many people, and other applications may have problems as well. We've talked with Shuttle about these problems, and they are working to find a solution. Hopefully, by the time we finish our investigations into X2 and 90nm Athlon 64 support, Shuttle will have an updated BIOS that will address the problems.

That's the biggest problem with the SN25P, and depending on your plans for your system, it may or may not be a critical factor in your purchasing decision. Disabling USB2.0 support appears to solve most of the stability issues, so we're hopeful that a BIOS update is all that will be required. Before you run out and buy one of the other 939 SFFs, however, we would suggest caution. All of the units in this roundup were released before the X2 launch, and while all of the manufacturers have released updated BIOS versions to allow them to function with the new processors, we haven't verified stability. We suggest that you check around at some forums before you purchase any of these units with an X2 processor, or else wait for our X2 compatibility update.

Final Thoughts on the SN25P

There are other aspects of the SN25P that we have come to notice during our reviews of the other systems. The SN25P certainly deserves credit for being the first PCIe 939 unit to hit the retail market, but is being first the same as being best? In retrospect, the SN25P actually continues to stand up well. The design is well thought out, the features are right, and performance is also good. The X2 support is the only serious blemish, but there are a few other things that we would like to see addressed.

First, the system has five fans keeping it cool, and most people will add a sixth in the form of their graphics card. Making a silent system with six fans is probably not possible, unless you unplug several of the fans. While we don't fault the SN25P for the inclusion of so many fans - cooling is among the best in the business, and overclocking scores reflect this - we would like to see some modifications for future XPC designs. The use of two 40mm fans at the rear of the case is one thing that we'd like to see changed. We simply haven't had a lot of positive experience with small fans; they have to spin faster to move the same amount of air as larger fans, and that, in turn, creates more noise. Several 40mm fans that we've used - including one in this Shuttle as well as another in the PC-Club Silencer - developed a slight vibration as well, which is extremely annoying and often requires you to replace the fan. It's not an easy change to make to the P chassis, but optimistically, Shuttle can avoid the use of smaller fans in a future "large SFF" chassis. A single 60mm fan would actually have a larger area than two 40mm fans, and hopefully, it would be less likely to have vibration or bearing whine problems.

Going along with the fans is the noise that they make, and rising ambient temperatures during the summer months have certainly had an impact on noise levels from the SN25P. When we reviewed it in early March, it was generally very silent. In July, we noticed that the fans were being kicked into higher RPM states a lot more frequently than before. You'll notice in our noise benchmarks that the SN25P is one of the louder units under stress testing. Despite the higher noise levels, for typical use, the CPU will not get hot enough to cause a dramatic increase in fan noise. Video/audio encoding and running games will often increase the amount of noise for 5 to 30 seconds at a time, but silence for a minute or more usually follows.

Besides fans and noise levels, the layout and design of the SN25P have proved itself to be better and worse than other designs. The tool-less design makes changing parts around relatively simple, and we continue to appreciate that feature. In comparison to the G5 chassis, however, the CPU heat sink and cooling mechanism are not as easy to install. We also wish that there was a better clip mechanism on the PCIe X16 slot, and with the rest of the tool-less features, the expansion slots are notably absent. It's ironic that you can remove the CPU heat sink in the G5 chassis without using any tools, but a screwdriver is basically required to mount the heat sink properly with the P chassis. The last change that we'd like to see in the design of the SN25P is the inclusion of a proper 6-pin PCIe power cable - just in case you don't have one around. We'll discuss this topic in more detail later, and the SN25P isn't alone in this regard. Given the cost of the systems and the high-end feature set, we'd really appreciate getting a good $5 cable thrown in "just in case".

Update: For those that may read this in the future, Shuttle has released an updated BIOS that addresses the X2 support issues. We haven't confirmed anything yet, but a new BIOS is available and it specifically addresses the USB2.0 + X2 problem.