Workstation GFX versus Gaming GFX in AutoCAD

Autocad will run on mainstream/gaming cards just fine. Lots of people use it. Mainstream cards will give you better performance than workstation cards of the same cost in professional programs despite the lack of optimization, since workstation cards are so overpriced.

A friend of mine does animation so yeah, one was a quadro and the other rig was with a gaming card - different worlds. quadro is much faster in terms of rotating rendered objects. The gaming card requires sometime to refresh.
There was one of the Quadro series that uses the same geforce chip, someone mod (disabled and enabled a few resistors) and unlocked the quadro feature on the card. Driver sees it as quadro. Not sure about the architecture now. OpenGL performs 10x better. But this was something like 4 years ago though.. not sure how it is now.

So we could say that gaming/mainstream cards will be decent for the job, maybe not top notch, but definitely do-able?

Well i wouldnt say decent also...cos frm what i have read, a high end workstation which would cost more than 500 bucks or so will perform equivalent to say a 8600GT or at max similar to 9600GT(but i think it wont) in games cos for games the cards are designed in such a way that they give very high fill rates (frame fill rates )but a workstation graphic card does not provide the required fill rate but it has a very high processing power which is required for rendering...

So basically workstation gfx are for processing power whereas desktop gfx are for faster fill rates(frame rates,..)

Oh I'm fully aware of that. I was saying from a workstation point of view. Will GAMING cards work in pro apps. I know that workstations are miserable at gaming.

They'll work fine. Most of the cards I work with are, in fact, gaming class cards rather than workstation cards. The workstation ones are just too pricey. They won't give you the performance of a workstation card, but the gaming cards get pretty close.

Okay, awesome. Saves me some buck. Plus flexibility. Now has anyone used both Nvidia and ATI cards for CAD? Any perform better or do you really see a pretty even playing field?

I have used both and purchase both for work (primarily for geo apps). They are very even nowadays for performance (used to favour nV), value tends to favour the ATi cards in the workstation market, but like for like performance is there for the various classes low/med/high, it's just the pricing that favours ATi as the underdog trying to leverage it's current design. There are some apps though that greartly favour one or the other (more SPUs vs more TMUs, etc), nothing does everything the best, but they all do them well enough.

My suggestion for you would either be the highest end desktop/gaming graphics card you can afford or else get one of the 'known' modable cards and then softmod it to use the Pro OGL drivers. However even then some apps will not recognize the available accelration without doing some lower level tweaking.
Alot of it depends on your apps, some are terrible on gaming cards and get clobbered by even cheap second hand workstation cards.

Here's a pretty descriptive guide for the Geforce mod;
http://www.techarp.com/showarticle.aspx?artno=539

And the FireGL mods are tweaked-out at Guru3D;
http://forums.guru3d.com/showthread.php?t=275174

This gives you the option of running the gaming card for the games and the workstation drivers for pro apps.

Be sure to take note of the cards listed because they need their workstation equivalents for them to work properly and reliably.