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XPS 8700, PCIe SSD, and the not really a PCIe x4 question
All,
Ok, so I've seen this thread:
http://en.community.dell.com/support-forums/desktop/f/3514/t/19536759
and I understand that the PCIe slot that looks like a PCIe x4 is really only wired for PCIe x1.
What I don't understand is why it's as slow as claimed. As I understand it, SATA 3.0 SSDs max out around the low to mid 500s MB/s,
But, PCIe x4 SSDs can go significantly faster.
HOWEVER, given that
- SATA 3.0 max ~ 600MB/s
- PCIe x1 3.0 max ~ 980MB/s
then shouldn't a PCIe SSD, even crippled by being plugged into this bogus x4 slot, still be able to outpace a SATA SSD? by around 50-60%?
However, what I've read suggests that such an arrangement with the PCIe x1 that looks like a x4 actually underperforms the SATA SSD.
Why is that the case?
speedstep
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47K Posts
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November 25th, 2016 07:00
You don't get full PCI-E bandwith on ALL SLOTS. The USB3 ports and other things use bandwidth. There are also 2 SATA3 ports on the motherboard that gobble up bandwidth. X1 wiring slows this down 400 percent more. Thats why full speed SATA3 cards need an X4 slot because those gimped wired slots are running at PCI-E 2.0 speed not 3.0 speed. X1 at PCI-E 2.0 speed is not SATA 3 FULL Speed.
The chipset and CPU and Bus cannot handle the max speed for pci-e on all slots and handle usb3 and and and simultaneously.