If he can tell you what graphics card is in the mac pro, would also give lots of indication to what model that it. Of course the easiest way is if he sends a screenshot of the system profilers hardware section.
If its the 2006 version then it will have a lot less performance then the one you are using at the moment. Several reasons for this:
- the 2.66Ghz 2006 version, like allready stated by "Transporteur", is probably the dual processor configuration. 2 dual core processors giving you a quad core machine. These processors will be based on the Core2Duo architecture which pretty old. Those CPU's have a lot smaller cache sizes, slow memory buses, and frontside busses. The 2009 machine you are using at the moment is an Intel Xeon "Nehalem" processor. The architecture of that processor is still one of the best available at the moment. Also you have 8 virtual cores. This means that although you are using a quad core machine the system sees 8 cores. Approximately 50% more performance. This is the "Hyper Threading Technology" by Intel. Also if im not mistaken the Nehalem processors feature the "turbo boost technology" aswell. This increases the speed of 2 of your cores when the others arnt needed. Thus increasing performance.
- Memory Type: The 2006 model has DDR2 Ram, running at 667mhz. The 2009 model uses DDR3 Ram, running at 1066mhz. This is a pretty big difference in performance.
-The graphics card (GPU): I guess the model he is selling has the nVidia Geforce 7300 GT. Your model at the moment probably the Geforce GT 120. The GT 120 is not a powerful card but more than enough for a average user. The 7300 GT in comparison is a joke

Not sure if it supports Open GL at all. The GT 120 does, thus increasing overall system performance as in Snow Leopard (10.6.x) OpenGL is used but obviously only with a card which supports it. GT 120 has more cores, has two dual link ports (7300 GT, has one dual link(max res. 2560,1600), one single link (max res. 1920x1200).
- optical drive in the 2006 model is a 16x Super Drive, the one you have currently is a 18x SuperDrive. Only minor differences here, no really noticeable performance difference, but thought i point it out.
- Power consumption to performance ratio is far worse then with the 2009 model. Mac Pro's back then had same or similar power consumption, but far less performance.
Im confused about something though: The person selling this mac pro said it was Clovertown, i think he was mistaken, misread something or just didt now 100%, or we dont know

wikipedia states these as the processors available in the 2006 version: ----->Two 2.66 GHz (5150) Dual-core Intel Xeon "Woodcrest"
Optional 2.0 GHz (5130), 2.66 GHz or 3.0 GHz (5160) Dual-core or 3.0 GHz (X5365) Quad-core Intel Xeon "Clovertown"<----
Unless of course it is a single processor Mac Pro, i and Transporteur thought it was dual processors. if we were wrong with the dual processors then what i said up top still stands. Difference is that you only have one dual core processor. not quad core. If the seller is correct with "clovertown", then it will be one 2.66Ghz Dual Core.
Now hard drive wise. You have 4 hard drive bays. One would be occupied by the 500gb drive. If you purchase a 1TB drive for like 90$ then u would put it into the 2nd drive bay. Giving you 1.5 TB overall. you could expand to 4TB, maybe even 8TB not sure.
IS IT WORTH $1200???? i would say no, look for it and you could get the same one for i'd say 900. Gotta look for it mate. For you to consider, a base model 21.5" iMac would have more performance, in every aspect, plus you'd have a isight, mic, decent speakers, keyboard, mouse, good screen. If you need the to however be able to upgrade all components, then mac pro is the way to go. You'd have the option of more graphics cards = more displays connected. Also far more storage.
WANT SOMETHING WITH THE SAME OR MORE PERFORMANCE AS THE ONE YOU ARE BORROWING?? Then im afraid you needa pay slightly more. 2009 models still go for roughly 2k, obviously ebay might help you out, if you dont want to or cant spend that money
Hope this helps, (im dyslexic, if something dont make sense, ask, ill rephrase

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