PCIE Risers - 4GB Decoding

I am looking into adding some risers to my rig. I am curios as I read that some rigs need to have an option in BIOS to unlock 4GB decoding yet it seems to be an Intel only issue.

Here are my questions:

  1. Is this a problem with AMD boards as well? If so, is there a particular year I need to have an updated BIOS for an AMD board to unlock 4GB decoding?
  2. Can a MSI FM2-A75MA-P33 run two 3GB 1060 GTX cards and mine to their potential?
  3. My motherboard has one PCIE16 and one PCIE1 slot. Will I run past the 4GB boundary for PCIE with 2 3GB 1060 GTX or is it 4GB per slot?
  4. I am looking at either getting a full PCIEx8 expansion card or just two PCIE risers. Would either of these prove to be incompatible with my board (considering the 4G decoding requirement)?

Thanks :man_dancing:
miner card
miner expansions

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Due not only to the Meltdown and Spectre threats, but the continued findings of security risks with an Intel processor (Intel Managemnet Security Flaws) that have been discovered over the past year, I am especially interested in building an AMD machine.

Does anyone know if the AMD machines have the restriction of under 4Gb decoding on the PCIE slots? Can this be opened in BIOS if so?

What would be the best recommendations for an AMD Mobo if my current board will not allow over 4GB decoding?

(I am aware that Spectre affects almost all chip designs; from Intel to AMD to ARM. Yet Spectre is harder to mitigate and lets face it, Intel has had some serious issues that past year to those of us who keep track of security issues.)

Is Spectre really a problem for mining machines? It would be a bad idea to keep your wallet on a mining machine anyway. If you’re just mining, and doing nothing else on it, what data or issues could Spectre cause? If your rig goes down just clean/reinstall.

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@root I appreciate your feedback but I am looking for a specific answer to AMD boards, not anything related to Spectre or Meltdown themselves. Thank you.

What the setting does is enable memory mapped I/O for a 64-bit PCIe device to 4GB or greater address space so that there is no shortage of address space or collision with address space reserved for other uses, such as ROM, RAM, Other I/O, Sound, etc. If memory mapped I/O isn’t an option then address space must be kept in the below 4gb address space, which can run out fairly quickly.

Above 4gb decoding should be an option on many Intel and AMD based boards. Not all boards need or include the option based on how expandable they are. Generally those designed for more than one video card will include it. Think motherboards with 3-x16 slots or 6 or more total slots. This is because each card put into the slots needs a certain amount of I/O space and lots of slots translates to the need for more address space.

If you have a motherboard with limited expansion capability, for instance a single x16 and a x1, then it’s possible the board doesn’t need the option.

To try to answer your questions.

  1. You should update your BIOS to the latest version anyway.

  2. Your MSI board looks like it will support one video card normally. I don’t know your board personally, but people online say they are using GTX 1060s and even higher end cards. With 2 riser cards, it looks like it should support two 1060s and should run them at full potential.

  3. With 2 cards it is likely you will not need above 4gb decoding. My Asus board runs 3 or 4 cards before I have to enable that.

  4. It is likely that your board will not support that 8x expansion card you have shown. I would go with 2 riser cards. Those expansion cards with 4 or 8 usb on them can work, but take lots of effort and the exact right motherboard, settings, etc.

Which processor do you have on the board now? A10?


Have a ryzen 5 1400 and MSI B350 PC mate mobo has option in bios to support 4 G decoding
Only new boards AM4 and TR4 have the possibility to supports 4G decoding.
so look of the possibilities and let us know also curios if that PCI cards works well

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I wish. No I only have the A4 model. I am looking at doing some upgrading in the next month ad I have always enjoyed AMD more than Intel even before so that’s the other reason I wanted to find out more on AMD and mining.

Thanks for your awesome and complete answer. Ill let you know towards the end of the month how the two riser cards work out when I get another 1060 (or better :pray:).

You rock @Obi-wan!!!

Thanks for your great feedback too @koso16! That helps me in my shopping list for the new build I want to do!!!