• Welcome to TechPowerUp Forums, Guest! Please check out our forum guidelines for info related to our community.

PCIe x16 slot speeds?

Zemfik

New Member
Joined
Feb 24, 2008
Messages
3 (0.00/day)
Likes
0
#1
Can someone explain to me what it means for dual PCIe x16 slots to have one at x16 and another at x4 (or x8, or whatever)? What exactly does this affect? Is it much worse than having them run both at x16? Is the X38 chipset the only one that supports both at x16?

Thanks.
 

Wile E

Power User
Joined
Oct 1, 2006
Messages
24,318 (5.89/day)
Likes
3,682
System Name The ClusterF**k
Processor 980X @ 4Ghz
Motherboard Gigabyte GA-EX58-UD5 BIOS F12
Cooling MCR-320, DDC-1 pump w/Bitspower res top (1/2" fittings), Koolance CPU-360
Memory 3x2GB Mushkin Redlines 1600Mhz 6-8-6-24 1T
Video Card(s) Evga GTX 580
Storage Corsair Neutron GTX 240GB, 2xSeagate 320GB RAID0; 2xSeagate 3TB; 2xSamsung 2TB; Samsung 1.5TB
Display(s) HP LP2475w 24" 1920x1200 IPS
Case Technofront Bench Station
Audio Device(s) Auzentech X-Fi Forte into Onkyo SR606 and Polk TSi200's + RM6750
Power Supply ENERMAX Galaxy EVO EGX1250EWT 1250W
Software Win7 Ultimate N x64, OSX 10.8.4
#2
Can someone explain to me what it means for dual PCIe x16 slots to have one at x16 and another at x4 (or x8, or whatever)? What exactly does this affect? Is it much worse than having them run both at x16? Is the X38 chipset the only one that supports both at x16?

Thanks.
When it says it's 16X+4X, that means the second slot is physically the size of a 16x PCIe slot, but is electrically only a 4X PCIe slot. Crossfire takes a signifigant hit using it, but still performs relatively well.

X38 is the only Intel platform chipset that supports both lanes at 16x for Crossfire. The 680i and 780i boards support dual 16X on the Intel platform, but are SLI only.

For AMD platforms, there are a few chipsets that support dual 16X.