ASRock Rack Delivers PCI Express 4.0 Card with Quad x4 M.2 Support

Source: ASRock Rack ASRock Rack Delivers PCI Express 4.0 Card with Quad x4 M.2 Support

It should come as no surprise that the ASRock Rack has provided another unusual and delightful addition to the world of PC hardware, and though intended for enterprise one wonders just what could be done with the product named RB4M2_G4.

As you can see from the above photo, this RB4M2_G4 is a PCI Express x16 card, and it has two M.2 slots on the front, each of which supports a Gen4 x4 device. But when we turn over this card we see that another pair of these Gen4 x4 slots reside on the back:

ASRock Rack RB4M2_G4 Back

Among the technical particulars we have physical dimensions of some 2.90 x 5.70 inches (73.65 x 144.78 mm), with an upstream interface of PCIe 4.0 x16. The internal connectors are four M.2, M-key (PCIe4.0 x4), supporting 22110/2280/2260/2242 form factors.

Pricing and availability are not listed on the product page, and the product does not appear to be for sale just yet.

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Sebastian Peak

Editor-in-Chief at PC Perspective. Writer of computer stuff, vintage PC nerd, and full-time dad. Still in search of the perfect smartphone. In his nonexistent spare time Sebastian's hobbies include hi-fi audio, guitars, and road bikes. Currently investigating time travel.


  1. willmore

    So the limit to ‘passive’ cards like this is that they rely on the motherboard/chipset/processor to handle the bifrication of the PCI-E bus. Not all devices support this, so using a card like this may be ‘iffy’. You may find that only one or two of your cards are recognized.

    If you think you can stuff this full of cards and plug it into any old 16x PCI-E slot, you’re in for a world of pain. Also, keep in mind that it has to be a full 16x slot as the card itself does no PCI-E switching to make up the difference. Also, performace will be determined by the PCI-E speed of the host–using an older MB with a PCI-E V2.0 16x slot will halve your speed.

    The ‘smart’ cards with a 16x to 4x(4x) switch in them is a lot more expensive, but a lot more compatable–and they also support the full 16x bandwidth to each card–so say you want to put 4x PCI-E 3.0 cards into a 16x PCI-E V1.0 host slot, you can get the full bandwidth to each card (but not all of them all at once). With a passive card, you’d get 1/4 the bandwidth (but you’d get it to each card simultaniously–which the ‘smart’ card would offer as well).

    Summary: this card is about as shady as some of those bitcoin mining 16x extension slots that use a USB 3.0 cable to route the PCI-E. Buyer beware.

    • Paul

      Those USB risers get the job done well enough. You don’t need the full bandwidth for mining. Not a good comparison.

    • CLINT

      What’s “shady” about this card? If purchaser doesn’t care to make informed decision before buying, can’t see why anyone except said purchaser is to blame for their poor choice.

      This type of card works great in many motherboards, including all the way back to socket 2011 or possibly before. I have two dual CPU 2011 boards, one of which can handle at least two of this kind of card. The other board doesn’t have PCIe bifurcation capability, but I knew that when I put it into service. There are plenty of single M.2 adapters available that work great in that board, including an interesting one that has two M.2 slots with a small ribbon cable that plugs into another x4 (or larger) slot.

      Several companies make cards like this, and they can’t be held accountable for buyers that don’t know what they’re doing.


      • Dr. Vibrato

        I fully agree. There is nothing shady about this card. The card being from Asrock RACK and moreso the soldermask being green indicate that this is not meant to be sold to clueless RGB nerds upgrading or building their next gaming rig, but rather intended for server and workstation scenarios, a domain where there exist plenty of CPUs and boards that support x4x4x4x4 bifurcation, and where any builder and maintainer of servers or workstations worth their business would have no difficulties in verifying x4x4x4x4-capability of any machine in their care…

  2. C,ram

    Dork. These are for epic servers. They have plenty of pcie4 lanes.

    • Gomp

      Imagine 4x4tb in a threadripper pro for editing videos… Sounds like a great idea!


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