Topic: Dont buy overpriced PCI-E raisers / extenders weight your options! (Read 9504 times)

I bought some $2 ebay ones and they have been working with my 5770's no prob
no molex power but they're lower-powered cards

Thanks for the replies. I've been trying to figure out if I need to use the molex powered extender cables.

I think I'll try adding cards slowly and see if it's stable before adding another card.

I'd like to save the $, but if it's required then I'll consider using your service 

There is ~375 Ohms between pins A2, A3, B1, B2 & B3 and the 6 pin molex's on the back of the card. Meaning different parts of the card are getting energized in different ways, and the 375 Ohms between A2 & A3, B1, B2 & B3 and the 6 pin molex's is there to prevent part of the card from routing ( drawing ) power through the entire card and damaging other components.

So to answer your question, both get power first while they don't at the same time and the number 42.

I have not personally had any problems, I can confirm that I've read about wires smoking and board sockets melting. I strongly believe that the vast majority of problems related to electrical failures and wire overloads has a lot more to do with poor connections and damaged wires ( internally ). If your card is getting power from a plug that is not making sufficient contact with the psu resistance will increase making that wire hotter thus becoming a worse conductor and the worse the conductor the higher the resistance; a cascading failure.

75W @ 12V = 6.25A



So are you asking why people use the raisers with the additional molex?

Ok. Can you confirm that the card will draw power from the power supply before the motherboard?
Or do we assume that every card draws 75 watts from the mobo 1st?

That is all dependent on the quality of the motherboard and gpu's power consumption.

Can you confirm that these powered cables are necessary when using 4 or 5 gpus?

Did I ever say I wanted to prevent power from being draw from the mother board?? Nope, didn't. You're living in a ridiculously paranoid world if you're worried about drawing any power through the mother board, its just plan silly to avoid it entirely, and you gain absolutely nothing from avoiding it, need I repeat, NOTHING. The PCI slots are designed to provided power for pci cards, so if you create additional pathways for current to flow then you will lower the amount traveling on each pathway, thus in turn increasing to total amount of current able to be drawn w/o damaging components ( traces and wires ); its really a pretty basic concept, re-read the  articles I posted, 
http://tinyurl.com/aynwg 
http://tinyurl.com/5s5llfo

have you ever check these pins A2 & A3, B1, B2 & B3 for continuity ?? They are all connected on the cards PCB - all the the same copper pad.  I can assure you that by isolating those 5 wires and detaching them from the riser / mobo entirely and reducing them to 1 - 16awg wire you are in fact decreasing the amount of current carrying capacity. You would be so much better off just leaving them connected to riser and the mother board and just have an additional 12v molex at your disposal. All Wires can be though of as resistors, b/c they all have some inherent amount of resistance.


Resistors in Parallel

    http://upload.wikimedia.org/wikipedia/commons/2/2a/Resistorsparallel.png

In a parallel circuit, current is divided among multiple paths. This means that two resistors in parallel have a lower equivalent resistance than either of the parallel resistors, since both resistors allow current to pass. Two resistors in parallel will be equivalent to a resistor that is twice as wide:

    http://upload.wikimedia.org/wikibooks/en/math/3/7/6/3760f431a4d755d2181151b4046d80a7.png

Since conductances (the inverse of resistance) add in parallel, you get the following equation:

http://upload.wikimedia.org/wikibooks/en/math/b/7/d/b7d797059343dbd0d2f8f8d09b06f1c2.png

For example, two 4 O resistors in parallel have an equivalent resistance of only 2 O.

To simplify mathematical equations, resistances in parallel can be represented with two vertical lines "||" (as in geometry). For two resistors the parallel formula simplifies to:

   http://upload.wikimedia.org/wikibooks/en/math/b/2/2/b22693aac2a2de84160944e7f0ee4fec.png



Another useful read

http://tinyurl.com/3u5crbb

"Electrical resistance

Voltage can be thought of as the pressure pushing charges along a conductor, while the electrical resistance of a conductor is a measure of how difficult it is to push the charges along. Using the flow analogy, electrical resistance is similar to friction. For water flowing through a pipe, a long narrow pipe provides more resistance to the flow than does a short fat pipe. The same applies for flowing currents: long thin wires provide more resistance than do short thick wires. "


Also,
 

1) *face palm*

2) Pins B10, A9 & A10 pull power through the mother board, so better pull those too

3) 1 milliohms = .001ohms


In the image below

Red indicates power source

Yellow Line = .3 ohms

Green Line = .3 ohms

Yellow & Green Line = .2 ohms

point - less resistance

http://image.bayimg.com/lakggaadh.jpg

Another thing,

Notice how in this picture all the lines are intact and the molex is just soldered to one side of the board.



http://image.bayimg.com/fakfhaadh.jpg

In any case the additional molex is just there to as a supplemental power inclusion point - not a replacement for all power going to the edge card ( pcie end that is )

2 issues i see
1) your not connecting up all the 12V lines. there are total of 5. so it may still pull power from the motherboard.
2) path of least resistance...  between getting power from motherboard or from the molex connector the difference in resistance is very small.
possibly measurable in milliohms. so it may still pull power from the motherboard.

I'm no electronics technician so i can't say for sure.

but i do know that hen i physically cut the ribbon wire and plug the 12v wires into a molex connector i am for sure not drawing any power from the motherboard.

Thats the same way I made a few of my previous ones but I really hated that free floating A1


So here is my solution

http://tinyurl.com/4xu7tnq

http://tinyurl.com/3k72u3m



but not cutting any of the wires the riser is no longer required to use additional molexs ( 12V+'s ) except when its required.
The current draw will always take the path of least resistance - http://tinyurl.com/aynwg http://tinyurl.com/aynwg


The molex plug is rigidly attached resulting in less flexing of the ribbons ( more importantly the solder joints which have no strain reliefs )

No more of this Zip Tie BS

http://image.bayimg.com/fakfhaadh.jpg


Assembly time is now ~2 minutes ( assuming I have to wait for the soldering iron / rework station to heat up. )


This is an extra btw if anyone wants it

3.25 BTC  gets it to you w/ FREE S&H to the lower 48 via USPS

http://tinyurl.com/4xu7tnq

http://tinyurl.com/3k72u3m

Seems like there will be a lot of unnecessary components which would be powered up ( idling ) which is a waste of energy.

This thread is very helpful. I previously bought from cablesaurus for my dedicated mining rig and thought it was a little pricey, but it worked, so I soon forgot. Now that prices are so low I'm pinching pennies. Still, I'd like to add 2 5870s to a 2u server I've got running for other purposes. Call me stupid for throwing $ at a mining rig, but I'm an ardent believer in Bitcoins.

Adequate power to the cards and the mobo is not an issue, but connecting the cards is. The Mobo has 2 8xPCI-e connectors (http://www.supermicro.com/Aplus/motherboard/Opteron2000/MCP55/H8DM3-2.cfm)

So I'm thing that 2 of these 8x to 16x cable 'adapters' would do the trick: http://www.9mart.com/products/2-Lots-PCI%252dExpress-Extension-Cable-8x-To-16x-Riser-Card-For-1U%7B47%7D2U.html

Thanks, and any advice from hardened miners is very welcome. Gotta watch those Btc lately!

Unfortunately the ones i have are in machines.
have to make some this weekend however... but this is what i do
i carefully cut the ribbon down where the 12V lines are on both sides (A2 & A3, B1, B2 & B3)
then i cut them away from the base of the card edge... and strip the wire ends.
solder a 16 gauge wire to it and connect the other end to a molex connector.

this completely isolates the 12V away from the motherboard and no power is pulled from the motherboard.
hard part is leaving the A1 wire (PRSNT1#) intact and not get it damaged or cut.
i have cut it once by accident and had to fix the wire.

I figured that it was well known that demand was also very limited hence not worth mentioning, I should have made it more clear. There is also VERY little demand and a very little limit to his supply.

Also, 1/2 hr?? geez care to post a pic of what you're doing that merits a half hour?? Each once runs me ~6 minutes.

Raiser 1X can be purchaser for less than U$s4 on Dealextreme!!! Check Out!!!

actually supply and demand is a factor...
demand is low... primarily it is only used by miners.
supply is also low... each molex connector is soldered on by hand which raises cost.
then it boils down to how much do want to gain in profit, how much time does it take to add a molex connector.

i add my molex connectors differently so it takes me at least 1/2 hour just to do 1 cable.
if i were to sell them i would be charging a lot more since i think my time is worth a lot.
but i don't sell them... I think I'm rambling now.

supply and demand would only justify his pricing IF there were a LIMITED supply, which is clearly not the case.

Supply and demand?

Plugged in and churning away. Turns out it's about 2" short of making the card mount nicely on a side card mount in the case so I'm running it open right now.

Going to order a PCI-e x1 extender to make it fit better. Will have to reconfigure some fans but then I will have managed to squeeze every last drop of hashing out of this particular box... for now

Would you ever plug you card in to a slot that forced you to install your card completely backwards. I mean come on, that's just ridiculous, what ever tard did that deserves to have the " black genie " come pay him a visit. Also, if you cant brush your teeth with out stabbing yourself in the ear you should probably just stick to mouth wash..... Oh and welcome to the internet!!!  mr.I've been buying stuff off the internets for 11 years, its nice to finale have you here we've missed you. Anyone else want to brag about how long they've been buying stuff of the internet via time oriented comparison? I was buying stuff off the internet since www.cyberslots.net was considered a highly addictive gambling site.

I've been purchasing stuff on the internet for well over 11 years. I was in on PayPal when they were still offering $10 for new accounts. I know the alternatives.

However, I have read enough threads of people having problems with extenders that paying an extra 110% for cablesaurus's seemed like a reasonable deal. One person even purchased an extender that was soldered on backwards. Backwards! Paying $5 extra to ensure my $250 card does not let out the black genie was a no brainer.