Ask Dan: The deadly temptation of Skulltrail

Date: 19 May 2008
Last modified 03-Dec-2011.

"And gold-plate the SATA cables, my good man."

I want to build a workstation around the Intel D5400XS Motherboard, with two Intel Core 2 Extreme QX9775 processors.

In order to install these processors, should I purchase them with or without the fans? They are an extra $400 each with the fans.

How much more powerful would this system be compared to a matched LGA775 based system with the same processor plugged in (both systems running either Windows XP 64, or Vista Ultimate 64 with 8Gb of 800MHz-FSB RAM)?

BTW I have never built my own system, so any guidance would be much appreciated. Am I in the right ballpark for hardware core components to set up the fastest system possible?

The system is not for funzies, it is specifically going to be for crunching as much image data as computationally possible per hour.

The video cards I am interested in are the Nvidia Quadro FX line (3700, 5500, or 5600). They need a stereo DIN connector, and having two of them plugged in (SLI) as well means a bigger power supply right (1000W - 1200W)?

I want to build a monster for around $15,000 Canadian, can you help me to spend it?


Hey, it's your money!

If it were me, I'd definitely go for a cheaper Xeon - because the Q9775 is, of course, just the renamed top model in the 5000-series Xeon line.

The Q9775 is, therefore, faster at stock speed than any of the other 5000-series quad-core Xeons. But the next step down from the Q9775 is the Xeon 5450, which runs at 3GHz to the Q9775's 3.2GHz. And that chip costs, what, 60% as much?

Going further down the 5000-series list, the best value (in dollars per stock clock speed) at the moment is likely to be the 2.33GHz Xeon 5410, which is likely to overclock quite well if you put it on a Skulltrail board (NOT if you put it on a plain Socket 771 server board, which will probably have no overclocking features).

You can get about five Xeon 5410s for the price of one Q9775. I'm just sayin'.

There actually is some sense to buying a Skulltrail board full of UV-reactive plastic and unnecessary heat-pipe chip coolers, because two-chip Socket 771 server boards don't seem to be a lot cheaper, and the Skulltrail board is more overclockable, has quality onboard sound, and supports both ATI CrossFire and Nvidia SLI for multi-graphics-card use - it's the only non-Nvidia-chipset motherboard so far that supports SLI. Most Socket 771 server boards don't even have two PCIe x16 slots, either; a Skulltrail board has four.

(I've no idea what the heck you need even two video slots for on a "number crunching" machine, but I'm going to assume you've got a good reason having to do with GPGPU applications, or something.)

I don't know what the deal is with the $CA400 CPU coolers you mention, but if you can't find a better deal somewhere, you could indeed use third-party CPU coolers and save a few bucks. Many coolers for Socket 771 chips are low-profile models for use in slim rackmount cases where the stock Intel coolers won't fit, but there are also some chunky copper coolers out there. By all means get a couple of those instead of the Intel coolers, if there's that big a price difference. Or, as I said, just get a cheaper Xeon and use the stock cooler that comes with it, which should be good for a pretty solid overclock.

Regarding how much faster an eight-core Skulltrail would be compared with an LGA775 system with one QX9775 on it... well, it'd be quite a lot more powerful, on account of how a QX9775, because it's really a Socket J Xeon with a fancy name, will not fit in an LGA775 socket.

LGA775 is single-CPU-socket-only, not that that's very much of a limitation now that you can get four cores in one physical CPU. The top-of-the-line CPU for LGA775 is the QX9650 Extreme, which is only 3GHz stock speed but otherwise broadly the same thing as the Q9775 - though it's significantly less ludicrously priced.

(This is because the real top-of-the-line LGA775 CPU is supposed to be the Core 2 Extreme QX9770, which really is the same inside as the QX9775. The QX9770 was one of those announced-but-not-buyable products for some time; I think it's actually genuinely made it onto the market now for $US1500-plus. It doesn't quite seem to have made it to Australia yet, though.)

For most applications, a high-end quad-core LGA775 system (including more sensibly priced Core 2 Quads that've been overclocked to three-point-something gigahertz, which is easy to do) will be indistinguishable from a dual-quad-core Skulltrail system. If you're doing something that's highly multithreaded, though, the system with twice as many cores may perform something approaching twice as well. There are all sorts of serious-server and scientific computation tasks that certainly can take advantage of those extra cores. Some other tasks, like hosting a bunch of game servers (on a LAN or a very fat Internet pipe), or doing some kinds of video effects generation or compression, or just charging up the Folding@Home or charts, will also benefit greatly from more than four cores.

By and large, though, four cores really are more than enough for almost everybody these days. And even if you do need eight cores, it's still hard to justify making that eight cores of overpriced Q9775, when almost-as-fast Xeons are so much cheaper.

Note also that some multithreaded tasks, of the sort traditionally done by Big Iron, require the particular specialty of those astronomically expensive systems: Bandwidth. Everywhere.

Multicore personal computers may now have raw CPU power far in excess of that of serious supercomputers of not so many years ago, but they do not have full-processor-speed access to RAM. What they have instead is relatively large, multi-level processor caches, which work pretty well for desktop computer tasks but fail miserably when you're reading and writing all over a giant dataset.

In those sorts of cases, an eight-core PC may not work any faster than a single-core system, because the RAM speed starves all of the CPUs for data to work on, and/or the opportunity to get rid of the results of their computation. There's no remotely economical solution to this problem, even if you've got fifteen grand burning a hole in your pocket - but it pays to look into how the task you want to do actually scales on PC hardware before dropping big bucks on something that won't actually work very much better than a much cheaper system.

Regarding the requirements of the Quadro FX cards: Yes, they do need a "stereo DIN connector", but only if you've got a 3D stereo monitor. Since about eight people in the world have one of those, I think you needn't worry too deeply about it unless you're planning to join their ranks.

And yes, you'll need a chunky PSU, but that's the least of your problems. By all means get yourself a giant PSU, since they don't cost a lot more than less capacious units from good brands. Get a kilowatt-plus unit made by a good company like Channel Well Technology (and sold under some other brand) and you'll be fine.


Meanwhile, back on planet Earth...

I am considering my options regarding upgrading my home workstation (HP xw6200 circa 2006) which although it felt pretty powerful when I bought it as it has 2x3.4GHz Xeon processors, I'm starting to feel the upgrade itch - particularly as I can't help but feel envious of the dual and quad core processors out there.

According to my HP manuals the motherboard chipset is an Intel E7525/ICH5R and the socket is dual 604 pin ZIF.

After perusing the Intel site, I think I have located two processors that may fit (the third on that page is my current processor). But before I go and do something stupid like buying them only to find that they won't fit, I thought I should ask - plus I've always wanted to ask you a question!

I have a horrible feeling that the motherboard/socket is now too old and I need to swap out the motherboard + processors. If this is the case, then should I be looking at Xeons, given the price premium? I do a lot of digital photo and video (personal) work at home and although I like the idea of using Xeon processors, I'm not really sure if I actually need them.


Yes, your two 3.4GHz single-core Xeons are pretty close to the fastest that'll work on that motherboard. There are indeed dual-core Xeons that use the same socket, but they're based on the Core 2 architecture instead of the Pentium 4 one, and I (and some other people) would be astonished if they worked.

Your best option, I think, is not to spend time and effort shoe-horning a new motherboard into your old system (it's probably possible, but you never know with brand-name computers...). Instead, buy a whole new no-brand clone from some place like m'verygoodfriends at Aus PC Market. This'll make it much easier to move data over from the old computer to the new one, and you can then use the old computer as a backup box or sell it.

Even if you value your time at $0 per hour, buying a whole new computer is still likely to make financial sense.

Your old system is broadly similar in CPU performance to a new low-end Core 2 Duo (or even a slightly overclocked entry-level Pentium Dual-Core). So for serious multi-core number-crunching, you will indeed get a considerable performance improvement from something like a base-model LGA775 Core 2 Quad.

There are inexpensive Xeons-in-name-only (see this Ask Dan) that're the same as the Core 2s and don't support multiprocessor operation, but there are also still "proper" two-socket Xeon boards that'll let you install two quad-core CPUs for maximum performance.

The top-end quad-core SMP-capable Xeon is, as I mentioned above, actually the super-overpriced Core 2 Extreme QX9775, the CPU around which Intel's flagship "Skulltrail" gaming system is built.

But if you want SMP at a more reasonable price, there's nothing stopping you getting a Skulltrail motherboard and putting a couple of much cheaper quad-core Xeons on it.

Even such a "sensible" 2-processor 8-core system will still cost you a lot more dollars per unit of computing power than would a humble Core 2 Quad, though. So if I were you, I'd get a low-end Core 2 Quad on an overclocking-friendly motherboard (which'll almost certainly let you get another 20% of CPU speed without sacrificing any reliability at all) that uses DDR2 RAM (because there's still no real need for the speed of DDR3, and DDR2 is so cheap as to be almost free these days).

AusPC have several pre-specced systems which let you play around with all this stuff about as easily as is possible. If you buy a whole computer worth of components, they'll also assemble it for free - which is a very good way to make sure you haven't accidentally specified a PSU that doesn't have enough plugs for the other stuff you've bought, or a CPU that won't work on your motherboard, or whatever.

Do feel free, of course, to spec up a computer at AusPC and then buy it from someone else. Especially if you don't live in Australia, because Aus PC Market only deliver to Australia (and New Zealand, though NZ customers may well be able to find a cheaper source for something the size and weight of a whole PC).

Australian shoppers can buy all kinds of PC hardware from Aus PC Market.
Click here to order!