On Wed, Oct 14, 2020 at 2:56 PM Grant Edwards <grant.b.edwa...@gmail.com> wrote:
> On 2020-10-14, antlists <antli...@youngman.org.uk> wrote: > > On 14/10/2020 19:58, Grant Edwards wrote: > >> On 2020-10-14, antlists <antli...@youngman.org.uk> wrote: > >> > >>> Does your mobo support NVMe drives? Just be aware my mobo is crap in > >>> that it says it supports two graphics cards, NVMe, etc, but if you > stick > >>> an NVMe in the second graphics card is disabled, or if you use both the > >>> NVMe slots you lose a couple of SATA ports, or whatever. Bit of a PoS > in > >>> that regard. > >> > >> I think that's pretty common. NVMe uses PCI-express channels that are > >> often shared with one of the PCI-express "slots" on the motherboard. > >> As a result you can't use both at the same time. > > > > Is that the sign of a cheap/rubbishy mobo? > > No. AFAICT, it's done even on good, highly rated mid-range desktop > motherboards. [I've never spent much time looking into high-end > server-grade motherboards, so I can't comment on those.] > > It's generally a limitation of the chipsets used. There are only so many PCI Express lanes to go around, so it's impossible to have all of the motherboard featured enabled at full blast at one time. Different motherboards have different solutions as to how they partition the lanes. For example, it's almost universal that if you have a single video card it uses 16 lanes, but if you put a second card in the first card will drop down to using 8 lanes and the other 8 lanes will go to the second video card. -- Manuel A. McLure WW1FA <man...@mclure.org> <http://www.mclure.org> ...for in Ulthar, according to an ancient and significant law, no man may kill a cat. -- H.P. Lovecraft
