Despite earlier rumors, it seems that even motherboards without X570 chipset can offer PCIe 4.0 on the Ryzen 3000 CPUs. AMD denied this during computex bit, Asus has now published a list of various X470 and B450 motherboards that should at least offer partially PCIe 4.0.

Remember that the option for PCIe Gen 4.0 popped up in several BIOSes on X470. Well, here it the thing, and as explained in our reviews the motherboard chipset chip and IO chip in the Ryzen 3000 processor, are the same thing. Yes, that's two  'chipset' chips. The one in the proc, thus is PCIe 4.0 and if you use X470 or another series 400 chipset, the interlinks are PCIe Gen 2.0. But that does mean that the CPU IO chip still can offer PCIe Gen 4.0 lanes to selected slots (graphics cards (x16) and one M2 slot (x4). 

So basically ASUS has outed a series of BIOS/firmware updates in the past few weeks, and that PCIe Gen 4.0 option is back. In Asia, some people have been trying to enable it, and it works on selected motherboards it seems. After enablement, the processors themselves provide 16 PCIe 4.0 lanes for graphics cards and four more lanes for M.2 NVMe SSDs. Remember, due to the chipset chip an X570 platform has PCIe 4.0 everywhere; X470 and B450 even use the old standard PCIe 2.0 with whatever runs over the chipset.

X470 and B450 boards that provide PCIe 4.0 from the CPU
The PCIe 4.0 lines of the CPUs should be at least partially usable with a new BIOS on various Asus motherboards with X470 and B450 chipset. In Asia, the manufacturer has lists of published BIOS updates and models (see thumbnail). These show that a whole range of the older boards with PCIe 4.0 x16 (graphics card) and PCIe 4.0 x4 (M.2-SSD) can even use PCIe 4.0 on the Ryzen 3000 proc.

All this is even true for the cheaper B450 motherboards. Some folks have been actively testing, and while it is a bit of hit and miss, out of 13 models, 10 offer the full PCIe 4.0 package from Ryzen; three Strix models did not offer full PCIe 4.0 for graphics cards but did support PCIe Gen 4.0 on the primary M2 unit. Interestingly enough for the more expensive X470 motherboards none of the six listed models worked with PCIe Gen 4.0. For these, the graphics card slot was PCIe 4.0 but running x8 or had no PCIe 4.0 available. The option on PCIe 4.0 in the listed Asus motherboards gets enabled through a BIOS update. Whether this already applies to all BIOS updates distributed at the end of June is not clear just yet.

Mydrivers reports that a PCIe 4.0 SSD on the TUF B450M-PRO gaming is said to reach full performance of around 5.0 GB/s reading and 4.2 GB/s writing. With the PCIe 4.0 option, the older X470 and B450 boards could be even more attractive as a cheaper alternative.

Ryzen 3000: Asus opens up PCIe 4.0 support for selected X470 and B450 boards