A desktop CPU vs a server class CPU. Not the same.
Very much the same, except for ECC ram support and dual processor support (moot in the mac pro), they are going to be identical down to the transistors and the performance in single CPU configs.
But the desktop chips are overclockable, bringing 10-30% more performance for a lower price. My quad core PC I built two years ago is still faster than the fastest imac config. And I spent over $1000 less. That difference paid for software upgrades and then some.
Is the RAM in that machine ECC? It is in the Mac Pro. It's more expensive than conventional RAM for a reason.
The rest of the mac world gets along just fine without ECC RAM. Without it, a workstation for video or 3d will do just fine. You can get more ram for your money by not going with ECC. From what I've found the only thing I got from ECC ram in the past was more expensive and harder to find RAM.
2x graphics cards capable of driving 3 4k resolution displays vs 1x graphics card designed for gaming at 1080p. Again, not the same.
Nope, not the same. Better. MUCH better for OpenCL 3d rendering in indigo as some have expressed interest in. GPU renderers need to load their scenes into ram on the video card. 6GB vs 2gb. If you so choose, with the leftover budget you could get 2 3GB cards for the same price.
That Titan was aimed squarely at the CUDA crowd. 6GB of VRAM isn't much of a gaming feature, as it is a 3d rendering / CUDA / OpenCL feature. It's a beast.
Also a gaming card has very very different needs to a workstation card.
Not for Open CL / Cuda and the bulk of graphics apps out there. There are exceptions, like your CAD program or Maya. But they are divas and everyone secretly hates them for it!
I have a workstation PC at work. The graphics card is from the nVidia Quadro family. It is specifically designed for the type of work (GIS and CAD) that I do. It is more expensive than the equivalent in the GeForce family, and would stink at gaming with a very low FPS count. It is, however significantly faster than a GeForce doing the work it's designed to do. I know this because I've benchmarked them. Using both benchmarking software used in CAD applications (Bentley do one) and a seat of the pants how does it actually perform using the software I use (literally someone standing over me with a stopwatch timing screen refreshes).
That varies depending on software. I use Cinema 4d, and it gets more benefit from more GPU cores and GPU ram. Workstation cards don't do didly squat for many applications over gaming cards. I don't doubt your CAD program requires it though. I used to use Maya, and they basically used to say "get a workstation card or we technically don't support your platform."
It sucks.
The graphics chipsets in the Mac Pro are designed and optimised specifically for the kind of tasks that a Mac Pro would be typically used for (video editing, CAD, 3D rendering, Adobe CS).
Video editing, 3d rendering, and Adobe CS will fly on gaming class cards. Much faster than workstation cards for the price. The iMac I'm on right now gets wonderful acceleration in FCPX and Adobe Premiere CC.
The Mac Pro is overpriced, however it uses some of the most kick ass parts available for the type of work it is designed to do and to produce something that used exactly the same components PC wise would also be more expensive than the system you pulled down the details of.
When comparing the exact same components, Apple has always been competitive or cheaper with their Xeon class systems.
But low end, single core Xeon systems used for most graphics work remain a poor investment regardless of platform. And that's all that Apple is building this time.
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My biggest concern here is the motherboards, and the mess of drivers. I've had my hands in the guts of Macs since the days of the SE30, but I know crap about motherboards, and I've heard horror stories about drivers on BYO systems. Have no idea how to find a good motherboard, what the memory busses are and what their performance is.
That said.. $500ish is borderline on the savings being worth it for what I hope would be a 6 year investment.
I was scared of that, too. After some internet research and watching some youtube vids, I was ready to try my first build.
Windows 7 handled all the drivers for me the first time I connected my franken-machine to the internet. It downloaded drivers for everything and I was good to go 15 minutes later, humming along at 4.2 GHz base speed.