AMD Ryzen are compatible with FMA4 instructions, something that was unknown
AMD Zen processors, such as AMD Ryzen, are found to support FMA4 instructions for linear algebra.
The launch of the Zen architecture that brings AMD Ryzen, AMD Ryzen Threadripper, and AMD EPYC to life, but brings with it the removal of support for the FMA4 instruction set, offering only support for the FMA3 instruction set. The Level1TEchs channel has found that all AMD Zen processors do indeed support FMA4 instructions, even though this instruction set is not present in the operating system itself.
They discover that officially AMD Zen processors like AMD Ryzen support FMA4 instructions.
The Fused Multiply Add instructions are used mostly for linear algebra calculations, making the process more efficient. FMA3 and FMA4 do not belong to different generations of the instruction set, it only indicates the number of operands per instruction and this is determined by the digit of these instructions.
The reasons why AMD did not introduce FMA4 in the Zen architecture is unknown, but some developers have speculated that the inclusion of these instructions by AMD series flawed, despite being 33% more efficient.
AMD first introduced FMA3 instructions in the AMD FX in 2012, while Intel added it in 2013 with the introduction of the Haswell architecture to the market. Intel was the one who popularized this type of instructions and that has made Intel processors somewhat more stable.
Level1Techs has used the program to test this type of instructions called OpenBLAS FMA4, which certifies that the AMD Zen offer support for FMA4 and that they do not give the error of 'illegal instruction' and the processor continues with the operation. Additionally, it is interesting because it is not exposed as a CPUID bit and the operating system has no knowledge of whether the instructions are compatible with the processor.
It should be noted that in linear algebra the FMA4 instructions are much more efficient than the single and double precision AVX.
