Bitcoin Forum

Since mining works fine in a 1x PCIe slot, why not go even slower with the conventional PCI bus? ;)

I bought one of these adapters for testing ($28 incl. shipping on Ebay) and it seems to work fine. HD5870 at 900 MHz gives 354 Mhash/s, which is no different from running it in a 16x PCIe slot. Now I can fit even more cards in this single mobo :)

There are just a few practical considerations. PCI is a shared bus, so performance may go down with more than one of these adapters. Also, PCI only gives 25 W of power, vs. 75 W of PCIe, but this does not seem to be a problem when the card is powered externally. Mounting the card is yet another issue, since this is basically a riser card.

Also, X refused to start in the usual way, but it worked after setting BusID explicitly. In my case, it was

BusID  "PCI:6:0:0"

The exact number can be seen from lspci, in a slightly different format like 06:00.0 in this case. The line goes in the Device section of xorg.conf.

(using Linux 2.6.37.5, fglrx 10.12, SDK 2.1)

I considered this a while back, but decided that my current mining cluster (9*5870) was enough. With the current difficulty I can't convince myself that buying more 5870s is a good idea!

Having said this, there do exist PCI bridged risers that will convert a single PCI slot into 3 PCI slots which (assuming mechanical and power issues could be solved -- flexi riser cables, meccano, multiple PSUs) would allow an insane number of GPUs to be hosted by a single CPU.

These are based on the fact that PCI is a shared bus, so you can basically add things in parallel without much electronics. In total it is slower than a 1x PCIe channel, so there will be limits to scaling this way.

There are also PCI Express splitters/hubs, which need a little more electronics, but the total capacity is likewise divided. For example here

http://www.magma.com/expressbox7x8RASG2.asp/

yeah I see a few of the auctions on ebay... $0.99 for the part, $30+ in shipping! What a drag for such a simple part.

I think every way that you can go with these will probably cost you more than another rig.
Interesting but I don't think it will be practical in the end.

Let me know if you find one though and thanks for the links / testing.

bumping old post.

https://i.imgur.com/Zi02K.jpg

these can be sourced from aliexpress for $22.99 inc postage, cheaper if bought in bulk.

Um.
You realize that one goes from PCI Express TO regular PCI, and not the other way around?
Make sure you get one that goes from PCI TO PCI Express, and then find a price for that.

wow, its not my day today :P


Here is a PCI -> PCIE adapter for $24.99 inc postage.

http://www.aliexpress.com/product-gs/492197522-PCI-to-PCI-E-PCI-Expresscard-card-X1-X4-X8-X16-Adapter-New-wholesalers.html

https://i.imgur.com/qYyk8.jpg

I just got a PCI to PCIE adapter from Monoprice:

http://www.monoprice.com/products/product.asp?c_id=108&cp_id=10304&cs_id=1030406&p_id=7001&seq=1&format=2

It looks to be the same one you can order from Chinese suppliers on Ebay, and the price is the same ($25 including shipping and tax). The advantage is that it ships faster (only two days to Southern California  ;D).

For my Biostar A870U3, this was plug and play with a 1x --> 16x pcie riser (no Molex) and a fresh install of BAMT. I haven't added the extra card yet (going from 4 to 5), though, just testing this by switching one of my existing cards from a x1 pcie slot to the adapted pci slot - I'll update after I add the 5th card and report any issues. So far, at least, I'm not seeing any reduction in performance for the GPU in the pci slot. Nor am I seeing any significant increase in voltage at the wall (not that I was really expecting any). Some have said that you must use risers with Molex for these adapters, but in my case this isn't so. All my cards are undervolted to 0.95, but I did run them briefly at stock voltage without issue. But pci slots are only good for 25-35 watts (as opposed to 75 watts for pcie), so it's probably best to use risers with Molex at higher voltages (or for more power hungry GPUs). I may add Molex to one of my risers just to be safe. 

I have an extra 5850 gathering dust, so $25 to get it running in my rig is a no-brainer vs buying a new mobo. If you know for sure you are going to end up with 5+ GPUs on one board, I would just pay up for one that can do this without the adapters. But if you bought a cheap mobo (with two pcie x16 and two pcie x1 slots) initially like I did and later want to expand beyond 4 cards, this is a good way to go. I wish Biostar was still making the A870 - such a great board for mining, seems to do everything you ask a mining rig to do with minimum hassle.   

Careful of the connector temperatures and currents - I used a PCI->PCIe converter on a 4890 mounted in a rack server two years ago.  Burned the motherboard and produced a lot of smoke.  Binned the server.

You should've used a powered pci-e extender on top of that, 4890 is a power hungry card (like any 'gamer' card) and it draws too much power for the PCI itself to handle, remember PCI can supply 25W of power while PCI-E can supply 75W of power. Without powered extender it is only safe to connect low-end cards (probably with passive cooling) at most.

It was before powered extenders were available to me (it was two years ago).  I had been running 4850's fine - and it was well powered.  Just the current draw through a constrained point.

I'm wondering, was that 4890 overclocked? I'm going to use a powered extender just to be safe, but I ran for quite a few days without one on a 5850 undervolted to 0.95. I'm not entirely convinced it's necessary for undervolted 5850's, but the consequences of being wrong could be rather severe, so it's not worth the risk. I wish somebody made extenders with Molex other than Cablesaurus @$20. Yes, you can make your own, but the last thing I need is another little project. It's odd that for the pcie --> pci adapters you get molex, but not for the pci --> pcie. Seems backwards to me.

No, I tend to run stock clocks or low memory clocks depending on the project.  It was a good use for a P3 server at the time.