Can I add another ATI HD 5870 on Mac Pro mid 2010 with ATI HD 5870 ?

Yep, 30 month old thread discussing computers that are 6-7 years old. but we can't all afford new machines and want to keep what we spent a lot of money on running for a little longer.

I see no reason for starting a new thread about a subject that already has a thread and knowledgable contributors on. They get to get e-mail notifications and we get to hear what they have to say, without it being a shot in the dark as to wether they happen to chance upon our new thread, if we had created one. I know many people like to have a new thread for each question, but I feel it is more beneficial to keep as much in of about the same subject it eh same place,.

Cheers for those links, I'll take a look later.

One issue with your statement about Molex and 3-6 volts. that is wrong. all Molex connectors for HDD's and CD's etc prior to SATA all have 12 volt on the Molex, the yellow line is 12 volt.

I am at wok now, so will browse your links when I get back home.

Thanks for them

I do see this nice write-up on one persons How To add more GPUs and power them safely.

http://forums.macrumors.com/showthread.php?t=1866870

I had a chance to look at this thread. What a butcher he was! No tools, hacking at cables etc. I'd have made up my own cables using a better quality thicker gauge silicon wires and bought new crimps for the connectors from RS -Export / Farmell or similar.

You can buy the 8 and 6 pin housings and the new male/ female terminals for the housing for pennies

http://uk.rs-online.com/web/p/pcb-connector-housings/2332775/

Each terminal is rated at 5 amps max, manufacturers rated figures even with relatively thin 20 gauge wire. So a 6 pin can cope with 15 amps, so 180 W at 12 volt. If every one has ever opened up a standard PC PSU you will see that they usually have one or two 12 volt rails, so that big bunch of 8 or 10 yellow (or red ) lines all come from the same solder point on the PCB inside the PSU.

Even a small standard PC PSU will give enough to run a single card, thought I'd go for a quality one every time

The way I would have gone with his ready bought PSU in the macforum write up would have been to open up the PSU and create my own custom wiring loom, cutting soldering , heat shrink and brand new connectors and crimps, suing maybe 18 or thicker gauge wire.

I'd not advise others to do the same unless they are electronics minded , these switched mode PSU's create much much higher voltages inside and the caps often stay charged for a time and can bite the unwary if they short them out.

I do play with and repair these PSU's on an ad hoc basis, , thought generally it is cheaper to just dump them and buy another.

In the past I have strung them together for other uses, after major internal surgery.... I have many, (like a pile of 50 or more) old PC PSU's salvaged from scrappers. I strip them down and 'float the output' so that that output earth is floating in relation to input voltage. This allows them to be daisy chained to create higher voltage 100-150 volt 30 amps PSU's for bulk lithium battery charging for electric vehicles. But nowadays I can buy a 4kW SwM PSU for less than the cost in my time to build one out of multiple PC units

Yikes ..I'd give those Juicboxes a wide berth!!

http://www.hardocp.com/article/2011/01/24/epower_juice_box_450w_auxiliary_power_ supply_review/9#.VS1t5LrwzO4

http://forums.anandtech.com/showthread.php?t=2294169