For MBA (reference) 290 & 290X cards only!

The difference between the different bios versions is the voltage only!
All of these bioses have lower VDDC levels than the stock in order to reduce the power consumption and to improve the thermal.

The bios coding is following:

xxxxx-x-xx.y-yy

xxxxx = STILT (obviously )
x = M (purpose, = mining)
x/xx = P (Hawaii PRO) or XT (Hawaii XT)
y = Version Config (V for VID)
yy = SVI2 VID code in hex

Therefore STILTMXT-V3A is the miner bios for Hawaii XT (290X) with 3Ah VID (1.18750V) made by The Stilt

The VID indicator specifies the voltage of the highest performance DPM State(7).
On 290 cards the DPM7 state is 947MHz while on 290X it is 1000MHz.
The voltage for the other DPMs has been lowered in the same magnitude (excluding the DPM0).

The changes:

Bios Core: VER015.041.000.001.00374x (Hawaii A0)

- Elpida B-die performance issue fixed by rewriting the timings and the MC straps correctly.
- Hynix Gemma-die performance improved by rewriting the timings and the MC straps correctly.
- GPU EVV VDDC dependency removed, changed to static voltage levels (VID based)
- Advanced Fan Control (Fuzzy Logic) disabled, changed to look-up table (PWM 20% <50°C / 65% <75°C / 80% <85°C)
- Enhanced the VRM configuration, yielding >5% improvement in VRM efficiency on the medium leaking test samples.
- 50% of the RBs (ROP) shedded, one array (16) from each of the SHs (0/1) to improve the power and the thermal.

Notes:

All of the changes to the voltages or on the fan speeds can be altered.
The voltage and the fan control work as usual they are still adjustable by the display driver or application such as Afterburner (recommended).

There is no easy way to tell the default voltage of the GPU.
Therefore I suggest you use the following ballpark value:

On a 290X specimen with a medium level leakage properties the set voltage of 1.1875V results around 1.12V when measured with a DMM. The VRM controller telemetry (accessible with GPU-Z) will display slightly less, around 1.070V under load. So if your voltage at the stock settings is reported below 1.070V during mining you should select a bios version with less than 1.1875V default voltage. Likewise if the reported voltage is above the 1.070V during mining, do select the higher (or highest) voltage bios version.

The voltages can be fine tuned manually in case a perfect version is not found among the six versions.

The recommended memory frequency is 1375MHz - 1450MHz for Elpida and 1375MHz - 1475MHZ for Hynix.
Higher frequencies are possible but not recommended. The bandwidth and latency available at 1375MHz is enough to provide the optimal <100% saturation for a 290X GPU operating at 1000MHz (2816PPI). The absolute upper limit for the memory frequency is around 1500MHz for both of the memory types. This is because at this point the memory controller itself becomes unstable and therefore starts to produce errors. These errors are not visible as the usual artifacts so you might be getting millions of them before you see any actual issues. The only way to go beyond the 1500MHz limit without errors is to cool down the GPU properly.

At the same PPI 290 GPU (2560SP) requires slightly more bandwidth than 290X (2816SP).
At the 2816PPI (290 @ 1100MHz and 290X @ 1000MHz) the required bandwidth for 290 is around 1400MHz while for 290X it is 1375MHz.

Please do note that the GPU temperature and the temperature of the card (including the DRAM) have a vast effect on the memory overclockability and stability. Therefore please start performing the tests at 1375MHz MEMCLK and increase it from there by small steps if necessary.

Also please do note that Elpida card owners are likely to see higher temperatures and power consumption with the fixed bios, despite everything that has been done to reduce the power & thermal. This is because previously the GPU has been held back by the memory latency. Now that the GPU is working at full speed the power consumption and the temperatures will be higher. Watch your GPU and VRM temperatures!

DO READ AND UNDERSTAND THE FOLLOWING STATEMENT BEFORE YOU PROCEED:

- These bioses are intended for cards with LOW "ASIC Quality" (LESS than 72%). Using these bioses on cards with HIGHER than 72% "ASIC Quality" will make the GPU to run at higher VDDC levels than they were designed to (essentially overclocking / overvolting). Cards with low "ASIC Quality" have lower leakage levels and therefore their default VDDC and the ability to withstand higher VDDC levels is higher.
- Use these bioses only as the LAST RESORT, in case the V32 (for 290X) or the V34 (for 290) is unstable!
- These bioses are completely unofficial and have not been approved by AMD.
- Warranty will be void if these bioses are used (as usual).

These bioses are unsigned...
But as usual, signatures have no power here...
At least in this case...