Ok I'm a little bit confused about stating that the 650i doesn't support full x16 in SLI setup isn't right, at least not according to this:
http://ca.asus.com/products.aspx?l1=3&l2=11&l3=495&l4=0&model=1567&modelmenu=2
"(C55+MCP55P; a.k.a. nForce®650i SLI & nForce®570 SLI)" ? so it's a 650i and 570 SLI?
and check this review while you're at it...
http://www.pcstats.com/articleview.cfm?articleid=2104&page=1
You have ASUS to blame for the confusion. The fact is that the 650i "chipset" does not support 16x16 in SLI mode. Ever.
The C55 SPP (northbridge) has 16+1+1 PCI-E lanes and is (basically) the exact same NB chip used by the 650i Ultra, 650i, 680i LT and 680i "chipsets". Each of the 600-series "chipsets" is made up of that NB chip, plus some southbridge chip (chip + chip = chipset).
The 650i "chipset" is made up of the C55 SPP (northbridge) and MCP430 (C51) southbridge. The MCP430 SB chip doesn't have any extra PCI-E lanes, so the 650i and 650i Ultra "chipsets" are limited to just the PCI-E lanes provided by the SPP.
In the case of the 650i, the 16 lane group can be split into 8+8 for SLI operation (requires flipping a card over) - otherwise, it runs the first slot in 16x electrical mode (except for the ECS board, which always runs in 8x electrical mode - they didn't include a flip-card on the board, so I assume the other slot is always 'active' and also 8x).
In the case of the 650i Ultra, they just leave one of the 16x physical slots off the motherboard, so there's only one implemented, with the full 16x electrical.
In the case of the 680i, the southbridge is the MCP55XE, which provides the additional PCI-E lanes needed to implement 16x16 SLI mode, along with the extra 8x slot and maybe a few extras.
In the case of the 680i LT, the southbridge is the MCP55, which is actually has all the same features available to it, but/so differentiation is made at the motherboard and BIOS levels (on the nVidia Reference Boards, at least)... so they leave off a LAN port, and/or other features, to keep production costs down.
Finally, we get to the ASUS 'Plus' board. As far as I know, it came out prior to any announcment of the 'LT' series and, for whatever reason, ASUS decided to call it a "650i" based chipset. But, as you can see from above, that makes about as much sense as calling the 680i LT a 650i-based chipset. Basically, they used the same SPP chip as the other boards, but they used a southbridge (MCP) chip from an older AMD design.
It's still not crystal clear exatly what the actual differences are between that MCP and the ones used in the 680i LT and 680i chipsets (if any), but basically, the ASUS hybrid 'Plus' board does in fact do 16x16 in SLI mode and has other features not available on 650i chipset based boards - because it's
NOT a 650i-chipset-based board
.
(for all I know, ASUS buys the C55 SPP cheaper as a "650i" part than it pays for it as a "680i" part, so maybe that's where the naming came from - they call it "NVIDIA® Dual X16 SLI" but they further 'clarify' that with "(C55+MCP55P; a.k.a. nForce®650i SLI & nForce®570 SLI)", which is clear as mud)
see this makes perfect sense and I thank you for the time to clarify it, I've been looking to build a PC and this MOBO just seemed to standout because it has almost everything I would need at a very good price! (the SLi in specific) I guess I'm better off paying the extra 50 bux on the 680i board, which is almost identical to the PLUS board, but with a pure 680i chipset.
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