[PLUG] PCI cards and connectors

[Linh Pham]

re: dangling connector

The PCIe standard allows for open ended slots and the key in the slot
should prevent any movement of the card along the length of the
connector. Here should be a little bit of buffer between the last pin
and the end of the slot.

The primary power pins are on the first section of the slot anyway.

Personally, I think open-ended slots should be a standard for slots
shorter than x16. That gives you the option of slotting in a card with a
longer connector anywhere in case you need to use a specific link back
to the CPU vs I/O hub or PCIe switch.

On 2020-10-20 19:09 -0700, John Jason Jordan <johnxj at gmx.com> wrote:

> OK, I think the case I bought has two x8 slots, plus there is another
> shorter slot that is probably x4. None are long enough to be x16 slots.
> I know the Sonnet cards are x16, so that explains why their
> connectors are so long.
> 
> Now, from the beginning I thought that Sonnet engineers failed first
> grade arithmetic, because U.2 drives can only use four lanes, and each
> card can hold only two drives. The Sonnet cards wouldn't be any slower
> if they were x8 cards, so why bother making them x16 cards? And if my
> Magma case has two x8 slots, that I know are open ended (because I could
> push the cards all the way down), then I could just use these cards in
> this case.
> 
> That is, if not having all the card's connectors into the slot is OK.
> It bothers me, though. Sort of like plugging a 20amp plug into a 15amp
> outlet. Of course, the case connects by Thunderbolt 3, which is also
> just four lanes, so TB3 is the real limiting factor. I just want to
> avoid smoke and melted electronics.
> 
> Add the fact that the case that I bought is one of three possible TB3
> PCI expansion cases, and as far as I know, none have more than one x16
> slot, plus most are on back order until the end of the year. The one I
> bought is a used one from eBay.
> 
> 
> On Tue, 20 Oct 2020 18:27:23 -0700
> Linh Pham <question+pdxlinux at closedsrc.org> dijo:
> 
> >PCI Express cards typically come as x1, x4, x8 and x16 (number of
> >lanes) and the connectors correspond to the number of lanes and the
> >same with PCI Express slots.
> >
> >Some, but not all, PCI Express slots have an open end to accept cards
> >with more lanes than the slot is wired up for. But, the majority of the
> >slots are not open-ended and can only accept cards for that connector's
> >length or shorter.
> >
> >For instance, a close-ended x4 can only accept a x1 or a x4 card.
> >
> >What's even more fun is that a slot can be wired for fewer lanes than
> >it can actually physically handle. Thunderbolt docks are commonly that
> >way due to TB3 supporting a maximum of a x4 connection.
> >
> >Based on what I found on B&H, one slot is a x16 slot that's wired up
> >for x8 and two x8 slots. How that's wired up to the controller/PCIe
> >switch, I'm not sure.
> >
> >- Linh
> >
> >On 2020-10-20 18:18 -0700, John Jason Jordan <johnxj at gmx.com> wrote:
> >
> >> My two PCIe 3 cards got here a week ago and I mounted the four U.2
> >> drives on them while waiting for the case to show up. It finally made
> >> it today. (Fedex has put it on a truck for delivery every day since
> >> last Wednesday, and the driver finally decided to deliver it today.)
> >>
> >> The case is a Magma EB3T-V3 which the vendor assured me could take
> >> the two Sonnet Dual Fusion PCI cards. Well, I can push them down
> >> into the connectors, but some of the connectors on the cards do not
> >> make contact. That is because the connectors in the case are about
> >> 2.25" long and the connectors on the cards are about 3.25" long.
> >>
> >> I think I've been had, but I'd like some education about what kinds
> >> of connectors PCI cards are supposed to use. And what are the
> >> different connectors called? So far Duckduckgo hasn't come up with
> >> anything. _______________________________________________
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> >>
> >
> >--
> >Linh Pham
> >_______________________________________________
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-- 
Linh Pham