Topic: GUIDE - Make your own open frame rig. - page 2. (Read 138288 times)

Started hastily with a lego rig that grew to this:



When I needed to cool the cards better (run the fans at a lower speed, spread out cards), I found some scrap wood and my trusty nail-gun and the result exceeded my usual "just enough" approach...



(the 5830 will be hooked up when the cablesaurus shipment arrives)

hmm, is that keyboard an IBM Model M 1391401?  or just a newer copy of one?

Back about 10 yrs ago, I bought half a dozen of 'em new in box off of eBay for ~$120 (all w/ 1989 manufacture date)

and I'm on my 2nd as of now...

is a 6970 a "dual gpu" card?  how do i tell?

Oho, interesting. So do 16x slots have additional power available? I thought all the power was in the 1x section, or at least that is how all the extenders that I have seen have ever been soldered.

5870s drawing more than 5970s? WTF. Maybe I need more powered molexes, or maybe I should just switch to 5970s

Actually the exact opposite is true.  The PCIe spec limits current on the slot to 75W but most high end cards (those with 8pin PCIe power connectors) draw much less.  I measured wattage at ~30W for a 5970 across the extender.  A 5870 draws ~30W too.

So why is a single card worse?
          5970          5870
4 GPU  60W total   120W total
6 GPU  90W total   180W total
8 GPU 120W total   240W total


To be compliant a PCIe 1x device must draw <25W and a PCIe 16x device which identifies it self as high current drawless than 75W.  All devices must draw less than 10W until interrogated by PCIe controller (at boot).

It really comes down to how aggressive MB designer was in power distribution.  Take a board with 4 PCIe x16 slots & 1 PCIe x1 slot.  By the spec that could draw 325W however to save money the design may assume that only 200W will be drawn from the PCIe bus.  If designed for 200W then either configuration would be fine up to 6 GPU but the 8 GPU 5970 setup is 20% overspec.  If they cut corners and design the power distribution to handle 150W safely well you likely are going to cause damage to the board if using more than 5 cards.

Granted the shouldn't cut corners but the number of users who pull 300W+ across the PCIe bus are in a rounding error and beefy power distribution is expensive.

It gets worse when using PCIe 1x slots.  The more PCIe 1x slots less power the designer may anticipate as a realistic scenario as PCIe 1x slots should draw <25W and many (SATA controllers, USB3.0, sound cards, etc) draw <10W.

Sadly lots of boards are non-compliant and available power across PCIe bus isn't a stat provided to it is hard to predict but as a rule of thumb I would be more cocerned about overloading the board when:
1) Using more than 4 SLOTS (# of GPUs doesn't matter).
2) The board has less PCIe 16x slots and more PCIe 1x slots.
3) The board only has a 4 pin 12V connector not the higher current 8 pin 12V connector.
4) The board is more of a budget model (not crossfire certified, etc).

is a 6970 a "dual gpu" card?  how do i tell?