On Tue, Apr 14, 2020 at 10:26 AM Wols Lists <antli...@youngman.org.uk> wrote: > > On 14/04/20 13:51, Rich Freeman wrote: > > I believe they have > > to be PCIv3+ and typically have 4 lanes, which is a lot of bandwidth. > > My new mobo - the manual says if I put an nvme drive in - I think it's > the 2nd nvme slot - it disables the 2nd graphics card slot :-( >
First, there is no such thing as an "nvme slot". You're probably describing an M.2 slot. This matters as I'll get to later... As I mentioned many motherboards share a PCIe slot with an M.2 slot. The CPU + chipset only has so many PCIe lanes. So unless they aren't already using them for expansion slots they have to double up. By doubling up they can basically stick more x2/4/8 PCIe slots into the motherboard than they could if they completely dedicated them. Or they could let that second GPU talk directly to the CPU vs having to go through the chipset (I think - I'm not really an expert on PCIe), and let the NVMe talk directly to the CPU if you aren't using that second GPU. > > But using the 1st nvme slot disables a sata slot, which buggers my raid > up ... :-( > While that might be an M.2 slot, it probably isn't an "nvme slot". M.2 can be used for either SATA or PCIe. Some motherboards have one, the other, or both. And M.2 drives can be either, so you need to be sure you're using the right one. If you get the wrong kind of drive it might not work, or it might end up being a SATA drive when you intended to use an NVMe. A SATA drive will have none of the benefits of NVMe and will be functionally no different from just a regular 2.5" SSD that plugs into a SATA cable - it is just a different form factor. It sounds like they doubled up a PCIe port on the one M.2 connector, and they doubled up a SATA port on the other M.2 connector. It isn't necessarily a bad thing, but obviously you need to make tradeoffs. If you want a motherboard with a dozen x16 PCIe's, 5 M.2's,14 SATA ports, and 10 USB3's on it there is no reason that shouldn't be possible, but don't expect to find it in the $60 bargain bin, and don't expect all those lanes to talk directly to the CPU unless you're using EPYC or something else high-end. :) -- Rich
