how exactly did you lower vcore to 662mV?
Team red miner:
Navi21 (6800/6800XT/6900XT)
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TRM v0.8.1 added basic support for Big Navi cards (Navi21). This section will
be expanded as we do more work for this gpu generation. For now, the suggested
tuning process is quite simple:
1) Big Navis should run in A-mode (it's chosen by default). While the B-mode is
available, the value of the 128MB cache is degraded with a larger memory
footprint.
2) Windows is preferred over linux for now since you can choose the "fast timings"
under win which adds 1.0-1.5 MH/s. Testing was made on Adrenalin 20.12.1.
The AMD recommended driver (20.11.3) had bugs for handling clocks on our 6800.
3) To be able to lower voltage properly, you need to modify the powerplay table
with e.g. MorePowerTool. Install GPU-Z and MorePowerTool. Save the bios using
GPU-Z. Open MorePowerTool, select your Big Navi gpu in the dropdown list. If
necessary, load the bios to get a baseline configuration. Lower the "Power
and Voltage" -> "Minimum Voltage GFX (mV)" limit to the voltage you with to
run. Lower than 625mV is rarely stable, although we've been able to run at 612mV.
NOTE FOR 6800 USERS:
6800 users might also want to increase the SOC TDC limit in the same tab. It
was 30A for our test 6800 which caused throttling. Increase it to 32 or 33A.
Before doing so, you should verify in HWiNFO64 that you're really being
throttled though by checking the "GPU SOC TDC Limit" row. If it hits 100%,
you need to increase the power limit.
3) Clocks suggestions as starting point for further tuning (Windows with "Fast
Timing" selected, Linux can choose similar but will se lower hashrates):
6800: 1235 MHz core, 2124 MHz mem, 625 mV, SOC TDC +10% -> 62.6-62.7 MH/s.
6900XT: 1200 MHz code, 2138 MHz mem, 650 mV, 63.2 MH/s
Happy mining!
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Videos of the undervolt can be found in youtube
