Motherboards with a good number of PCIe slots

[SiliconWizard]

Looks like most recent ATX motherboards have a dramatically reduced number of PCIe slots (and M.2 slots are favored).

Do you guys know of any brands/models that offer like 5 PCIe slots (among which at least 4 slots x16) with the latest AMD or Intel processors support?

[Halcyon]

Supermicro.

https://www.supermicro.com/en/products/motherboards

You could look at something like the C9Z390-series which have four x16 physical slots (but not necessarily all at x16 speed) and one x1 slot. There is also the C7X99-OCE-F.
Or if you want the x16 slots to actually be x16, the C9X299-series boards would fit the bill.

If you look at their server-grade boards, there are some ATX offerings that might be suitable as well, like the X12DPL-series, but you're looking at Xeon processors at this price bracket.

[Someone]

As above, you're off into workstation or server boards to get that sort of configuration.

[SiliconWizard]

As above, you're off into workstation or server boards to get that sort of configuration.

Thanks, interesting (but not too surprising unfortunately) that while it was still the norm a few years ago on consumer motherboards, this has become a niche.

[Jackster]

AMD and Nvidia killing off consumer level dual GPU really put the nail in the coffin for decent motherboards with many PCIe slots.

There are a few high end gaming motherboards with them. See ASUS, Gigabyte and MSI.
Note that the consumer CPUs are maxing out at around 24 lanes so those multi x16 are running bifurcation, sharing or are just x4/x8.

Really depends on your application.
Do you need full bandwidth on each slot at the same time?

Otherwise as others have stated. Workstation/server setup. Plenty of options.
+1 for SuperMicro

If your application only needs to run for a short time or not use much power. Check eBay for old servers.
Many old machines out there with loads of slots but they chug power and are not very fast.

[SiliconWizard]

It's tightly related to the fact recent consumer CPUs have fewer PCIe lanes. The i9 13900K which is currently the top of their consumer line (is there anything else?) only has 20 lanes. Sure it's PCIe up to 5.0 so that's more bandwidth, but still only 20 lanes and more bandwidth as per 5.0 would only benefit recent enough cards that support it. Even their recent Xeon-W CPUs have 20 lanes.

A few years back, the top of their consumer CPUs had 40 lanes.

Again I do understand that 20 lanes of PCIe 5.0 beats the crap out of 40 lanes of PCIe 3.0 or even 4.0, but that is... as long as you got devices that support 5.0. And that's still fewer lanes, so fewer potential PCIe peripherals.

[Whales]

Alternative:  M.2 to fullsize PCIE cables and adaptors.  Limited lane count and not pretty.

Is it possible to make your own addon card that has a PCIE switch chip and a bunch more slots?  That's how my old motherboard did it anyway (not enough PCIE lanes to support all of the slots).

[DiTBho]

Routers and laptops have the same problem. 1 or 0 slots!? Wtf? Plus, lot miniPCIe cards are not properly described, causing confusion 

Computers ...

[eutectique]

I've got unused z170 pro gaming. It has 3 PCIe1 and 3 PCIe16 though. One M2 slot.

https://tweakers.net/pricewatch/457426/asus-z170-pro-gaming/specificaties/

[wraper]

There are no longer many PCI-E x16 on consumer boards because Crossfire and SLI are dead. Also generally you don't get that many PCI-E lines from CPU to make 4x PCI-E to operate even at x8 and NVMe take even more lines. For new stuff, options are to buy a Threadripper based motherboard. Also many motherboards have  x1 slots with open edge, so you can use them if you can run those x16 cards in x1 mode.

[Monkeh]

It's tightly related to the fact recent consumer CPUs have fewer PCIe lanes. The i9 13900K which is currently the top of their consumer line (is there anything else?) only has 20 lanes.

...

A few years back, the top of their consumer CPUs had 40 lanes.

Which is four lanes more than previous generations. Same goes for the chipsets. No consumer part had 40 lanes - 16 + 24 from the chipset. Today you can have 20 + 28.

No, i9 XEs aren't consumer parts, they're Xeons in drag.

[Doctorandus_P]

You probably won't find many of them in the consumer oriented market, The slot is mostly used for high-end graphics cards and these have a thickness of 2 or even 3 slots, so the connectors under them will be wasted anyway.

But for industrial computers it's common to have a connector for all 7 slots of and ATX board. Asrock also makes industrial MoBo's:

https://www.asrockind.com/en-gb/atx

[Zoli]

At this moment, AMD workstation and server CPU's has the most PCIe lanes(4.0, up to 96 IIRC) available, so look in that direction; and expect some premium to pay...

[SiliconWizard]

Yes, I've seen that AMD was the only one making CPUs with more PCIe lanes. The Threadripper series have an insane number of them!
So, that's where I'm gonna look next.

[olkipukki]

Looks like most recent ATX motherboards have a dramatically reduced number of PCIe slots (and M.2 slots are favored).

Do you guys know of any brands/models that offer like 5 PCIe slots (among which at least 4 slots x16) with the latest AMD or Intel processors support?

Why do you need so many PCIe slots?

ASRock makes Server/Workstation grades boards - www.asrockrack.com

For example, I'm using previous EPYC generations
https://www.asrockrack.com/general/productdetail.asp?Model=ROMED8-2T/BCM#Specifications

If 5 pcies are not enough, they have 7
https://www.asrockrack.com/general/productdetail.asp?Model=WRX80D8-2T#Specifications

Be ready to pay ~1K EUR just for a board.

P.S.
If you have a moderate workload and do not need a latest CPU, you can find a lot SuperMicro EPYC Gen1/Gen2 options on eBay