Cryptocurrency mining is still a thing, as you probably know by now. Every time there’s a spike in the value of mining digital currency, there’s an overwhelming number of sales that pick up for various things used for mining farms – cheap processors, stupidly slow RAM modules, motherboards with more than four PCI Express slots, and of course, graphics cards. But it’s not always possible to pack more than six PCIe slots into a board. There are specialised motherboards available for this purpose, but what if they’re out of stock? You can pick up a more expensive board, of course, but you’re still limited to six cards at most. This is the problem that MSI hopes to solve with a BIOS update that allows miners to use more GPUs than there are PCIe slots on the motherboard.
What MSI is offering here is a special function of the PCI Express protocol that allows adding in a larger memory address space in the BIOS in order to properly address more devices. “Above 4G Decoding” allows you to map the address space for hardware in a fully 64-bit system to a memory pool larger than 4GB. In 32-bit systems, multi-GPU setups would run into an issue where a fourth or even fifth GPU that pushed the address space needed over 4GB would result in every card having a lowered address space. With the 4G Decoding option enabled, it is possible to use multiple cards with a framebuffer larger than 4GB, which fixes existing issues with motherboards based on the Z100 and Z200 series Intel chipset not supporting more than four graphics cards in a system.
Simply put, 4G Decoding was disabled by default and couldn’t be changed by the user, which meant miners ran into the 32-bit memory map limit of 4GB.
MSI has a sizeable list of motherboards which now support this option when enabled, and there’s even a few other nifty things that they’ve done too. With the memory map limits gone, it’s possible to add much more than four cards to a system. If you make use of adaptors in the M.2 PCIe slots normally reserved for SSDs, you can add another two cards into the system. This is still much less than the twelve PCIe slots that the Biostar TB250-BTC Pro can boast about, but that board will be available in lower quantities compared to MSI’s other boards on offer here.
What is interesting as well is how MSI’s board capabilities compare when you look at the AMD socket AM4 motherboards. With the Bristol Ridge APUs in the system, the most you can address is five graphics cards on PCIe slots, with one via a M.2 adaptor. It’s not possible to do more than that, and that’s down to the way that the Promontory chipset on Bristol Ridge allocates PCIe lanes. Inserting a GPU into the main PCIe slot takes up all eight lanes of connectivity. Plugging in another card reduces that to four lanes on the main GPU, with four left to allocate. On some boards, one of those lanes is dedicated to a M.2 port connected directly to the processor, and three other PCIe slots are left. The sixth card is connected to the M.2 connector hosted on the third-party chipset found on the motherboard.
If you want more than that, it’s simpler to wait a little bit for the Ryzen R3 processors, which will still be cheap, and offer more connectivity.
Should any of you readers remain interested in jumping into the mining craze despite the recent difficulty increase, you’ll have to wait until more graphics cards come in stock to do it, or alternatively order in some of the specialised mining cards released by AMD and NVIDIA’s partners from overseas sources. A few other motherboard vendors might also have this feature enabled already, but it’s nice to see MSI figure out a solution for their customers, even if they aren’t picking up these motherboards for gaming purposes. Money’s money, right?