diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
new file mode 100644
index 000000000..54152c5ef
--- /dev/null
+++ b/.github/workflows/ci.yml
@@ -0,0 +1,279 @@
+name: Nimbus nim-beacon-chain CI
+on: [push, pull_request]
+
+jobs:
+  build:
+    strategy:
+      fail-fast: false
+      max-parallel: 20
+      matrix:
+        target:
+          # Unit tests
+          - os: linux
+            cpu: amd64
+            TEST_KIND: unit-tests
+          - os: linux
+            cpu: i386
+            TEST_KIND: unit-tests
+          - os: macos
+            cpu: amd64
+            TEST_KIND: unit-tests
+          - os: windows
+            cpu: amd64
+            TEST_KIND: unit-tests
+          - os: windows
+            cpu: i386
+            TEST_KIND: unit-tests
+
+          # # Minimal integration tests
+          # - os: linux
+          #   cpu: amd64
+          #   TEST_KIND: finalization-minimal
+          # - os: linux
+          #   cpu: i386
+          #   TEST_KIND: finalization-minimal
+          # # Requires GNU getopt
+          # - os: macos
+          #   cpu: amd64
+          #   TEST_KIND: finalization-minimal
+          # - os: windows
+          #   cpu: amd64
+          #   TEST_KIND: finalization-minimal
+          # # TODO - Bootstrap issue: https://github.com/status-im/nim-beacon-chain/issues/1725
+          # # - os: windows
+          # #   cpu: i386
+          # #   TEST_KIND: finalization-minimal
+
+          # Mainnet integration tests
+          # - os: linux
+          #   cpu: amd64
+          #   TEST_KIND: finalization-mainnet
+          # # - os: linux
+          # #   cpu: i386
+          # #   TEST_KIND: finalization-mainnet
+          # # - os: macos
+          # #   cpu: amd64
+          # #   TEST_KIND: finalization-mainnet
+          # - os: windows
+          #   cpu: amd64
+          #   TEST_KIND: finalization-mainnet
+          # # TODO - Bootstrap issue: https://github.com/status-im/nim-beacon-chain/issues/1725
+          # # - os: windows
+          # #   cpu: i386
+          # #   TEST_KIND: finalization-mainnet
+        include:
+          - target:
+              os: linux
+            builder: ubuntu-18.04
+          - target:
+              os: macos
+            builder: macos-10.15
+          - target:
+              os: windows
+            builder: windows-2019
+    name: '${{ matrix.target.os }}-${{ matrix.target.cpu }} (${{ matrix.target.TEST_KIND }})'
+    runs-on: ${{ matrix.builder }}
+    steps:
+      - name: Cancel Previous Runs
+        uses: styfle/cancel-workflow-action@0.5.0
+        with:
+          access_token: ${{ github.token }}
+
+      - name: Checkout nim-beacon-chain
+        uses: actions/checkout@v2
+        with:
+          path: nim-beacon-chain
+
+      - name: Derive environment variables
+        shell: bash
+        run: |
+          if [[ '${{ matrix.target.cpu }}' == 'amd64' ]]; then
+            ARCH=64
+            PLATFORM=x64
+          else
+            ARCH=32
+            PLATFORM=x86
+          fi
+          echo "::set-env name=ARCH::$ARCH"
+          echo "::set-env name=PLATFORM::$PLATFORM"
+
+          # libminiupnp / natpmp
+          if [[ '${{ runner.os }}' == 'Linux' && '${{ matrix.target.cpu }}' == 'i386' ]]; then
+            export CFLAGS="${CFLAGS} -m32"
+            echo "::set-env name=CFLAGS::$CFLAGS"
+          fi
+
+      - name: Install build dependencies (Linux i386)
+        if: runner.os == 'Linux' && matrix.target.cpu == 'i386'
+        run: |
+          sudo dpkg --add-architecture i386
+          sudo apt-fast update -qq
+          sudo DEBIAN_FRONTEND='noninteractive' apt-fast install \
+            --no-install-recommends -yq gcc-multilib g++-multilib \
+            libssl-dev:i386 libpcre3-dev:i386
+          mkdir -p external/bin
+          cat << EOF > external/bin/gcc
+          #!/bin/bash
+          exec $(which gcc) -m32 "\$@"
+          EOF
+          cat << EOF > external/bin/g++
+          #!/bin/bash
+          exec $(which g++) -m32 "\$@"
+          EOF
+          chmod 755 external/bin/gcc external/bin/g++
+          echo '::add-path::${{ github.workspace }}/external/bin'
+
+      - name: Restore MinGW-W64 (Windows) from cache
+        if: runner.os == 'Windows'
+        id: windows-mingw-cache
+        uses: actions/cache@v1
+        with:
+          path: /external/mingw-${{ matrix.target.cpu }}
+          key: 'mingw-${{ matrix.target.cpu }}'
+
+      - name: Restore Nim DLLs dependencies (Windows) from cache
+        if: runner.os == 'Windows'
+        id: windows-dlls-cache
+        uses: actions/cache@v1
+        with:
+          path: /external/dlls-${{ matrix.target.cpu }}
+          key: 'dlls-${{ matrix.target.cpu }}'
+
+      - name: Install MinGW64 dependency (Windows)
+        if: >
+          steps.windows-mingw-cache.outputs.cache-hit != 'true' &&
+          runner.os == 'Windows'
+        shell: bash
+        run: |
+          mkdir -p external
+
+          curl -L "https://nim-lang.org/download/mingw$ARCH-6.3.0.7z" -o "external/mingw-${{ matrix.target.cpu }}.7z"
+          7z x -y "external/mingw-${{ matrix.target.cpu }}.7z" -oexternal/
+          mv external/mingw$ARCH external/mingw-${{ matrix.target.cpu }}
+          echo '::add-path::${{ github.workspace }}'"/external/mingw-${{ matrix.target.cpu }}/bin"
+
+      - name: Install DLLs dependencies (Windows)
+        if: >
+          steps.windows-dlls-cache.outputs.cache-hit != 'true' &&
+          runner.os == 'Windows'
+        shell: bash
+        run: |
+          mkdir -p external
+
+          curl -L "https://nim-lang.org/download/windeps.zip" -o external/windeps.zip
+          7z x -y external/windeps.zip -oexternal/dlls-${{ matrix.target.cpu }}
+          echo '::add-path::${{ github.workspace }}'"/external/dlls-${{ matrix.target.cpu }}"
+
+      - name: Install build dependencies (MacOS)
+        if: runner.os == 'macOS'
+        shell: bash
+        run: |
+          brew install gnu-getopt
+          brew link --force gnu-getopt
+
+      - name: Get latest nimbus-build-system commit hash
+        id: versions
+        shell: bash
+        run: |
+          getHash() {
+            git ls-remote "https://github.com/$1" "${2:-HEAD}" | cut -f 1
+          }
+          # nimHash=$(getHash nim-lang/Nim '${{ matrix.branch }}')
+          # csourcesHash=$(getHash nim-lang/csources)
+          # echo "::set-output name=nim::$nimHash"
+          # echo "::set-output name=csources::$csourcesHash"
+          nbsHash=$(getHash status-im/nimbus-build-system)
+          echo "::set-output name=nimbus_build_system::$nbsHash"
+
+      - name: Restore prebuilt Nim binaries from cache
+        id: nim-cache
+        uses: actions/cache@v1
+        with:
+          path: nim-beacon-chain/NimBinaries
+          key: 'nim-${{ matrix.target.os }}-${{ matrix.target.cpu }}-${{ steps.versions.outputs.nimbus_build_system }}'
+
+      - name: Build Nim and associated tools
+        if: steps.nim-cache.outputs.cache-hit != 'true'
+        shell: bash
+        working-directory: nim-beacon-chain
+        run: |
+          ncpu=
+          ext=
+          case '${{ runner.os }}' in
+          'Linux')
+            ncpu=$(nproc)
+            ;;
+          'macOS')
+            ncpu=$(sysctl -n hw.ncpu)
+            ;;
+          'Windows')
+            ncpu=$NUMBER_OF_PROCESSORS
+            ext=.exe
+            ;;
+          esac
+          [[ -z "$ncpu" || $ncpu -le 0 ]] && ncpu=1
+          echo "::set-output name=ncpu::$ncpu"
+
+          make -j$ncpu ARCH_OVERRIDE=$PLATFORM CI_CACHE=NimBinaries V=1 update
+
+          # Cached in "windows-dlls-cache" and exported globally
+          # if [[ '${{ runner.os }}' == 'Windows' ]]; then
+          #   make -j$ncpu ARCH_OVERRIDE=$PLATFORM fetch-dlls
+          # fi
+
+      - name: Smoke test the Beacon Node and Validator Client with all tracing enabled
+        if: matrix.target.TEST_KIND == 'unit-tests'
+        shell: bash
+        working-directory: nim-beacon-chain
+        run: |
+          make -j$ncpu ARCH_OVERRIDE=$PLATFORM LOG_LEVEL=TRACE NIMFLAGS="-d:testnet_servers_image" beacon_node
+          make -j$ncpu ARCH_OVERRIDE=$PLATFORM LOG_LEVEL=TRACE NIMFLAGS="-d:testnet_servers_image" validator_client
+
+      - name: Get latest fixtures commit hash
+        if: matrix.target.TEST_KIND == 'unit-tests'
+        id: fixtures_version
+        shell: bash
+        run: |
+          getHash() {
+            git ls-remote "https://github.com/$1" "${2:-HEAD}" | cut -f 1
+          }
+          fixturesHash=$(getHash status-im/nim-eth2-scenarios)
+          echo "::set-output name=fixtures::$fixturesHash"
+
+      - name: Restore Ethereum Foundation fixtures from cache
+        if: matrix.target.TEST_KIND == 'unit-tests'
+        id: fixtures-cache
+        uses: actions/cache@v1
+        with:
+          path: fixturesCache
+          key: 'scenarios-${{ steps.fixtures_version.outputs.fixtures }}'
+
+      - name: Get the Ethereum Foundation fixtures
+        if: >
+          matrix.target.TEST_KIND == 'unit-tests' &&
+          steps.fixtures-cache.outputs.cache-hit != 'true'
+        shell: bash
+        working-directory: nim-beacon-chain
+        run: |
+          scripts/setup_official_tests.sh fixturesCache
+
+      - name: Run nim-beacon-chain tests
+        if: matrix.target.TEST_KIND == 'unit-tests'
+        shell: bash
+        working-directory: nim-beacon-chain
+        run: |
+          make -j$ncpu ARCH_OVERRIDE=$PLATFORM DISABLE_TEST_FIXTURES_SCRIPT=1 test
+
+      - name: Run nim-beacon-chain testnet0 (minimal)
+        if: matrix.target.TEST_KIND == 'finalization-minimal'
+        shell: bash
+        working-directory: nim-beacon-chain
+        run: |
+          ./scripts/launch_local_testnet.sh --testnet 0 --nodes 4 --stop-at-epoch 5 --log-level DEBUG --disable-htop --enable-logtrace --data-dir local_testnet0_data --base-port $(( 9000 + EXECUTOR_NUMBER * 100 )) --base-rpc-port $(( 7000 + EXECUTOR_NUMBER * 100 )) --base-metrics-port $(( 8008 + EXECUTOR_NUMBER * 100 )) -- --verify-finalization --discv5:no
+
+      - name: Run nim-beacon-chain testnet1 (mainnet)
+        if: matrix.target.TEST_KIND == 'finalization-mainnet'
+        shell: bash
+        working-directory: nim-beacon-chain
+        run: |
+          ./scripts/launch_local_testnet.sh --testnet 1 --nodes 4 --stop-at-epoch 5 --log-level DEBUG --disable-htop --enable-logtrace --data-dir local_testnet0_data --base-port $(( 9000 + EXECUTOR_NUMBER * 100 )) --base-rpc-port $(( 7000 + EXECUTOR_NUMBER * 100 )) --base-metrics-port $(( 8008 + EXECUTOR_NUMBER * 100 )) -- --verify-finalization --discv5:no
diff --git a/README.md b/README.md
index 011d1123c..a88134cf3 100644
--- a/README.md
+++ b/README.md
@@ -2,6 +2,7 @@
 
 [![Build Status (Travis)](https://img.shields.io/travis/status-im/nim-beacon-chain/master.svg?label=Linux%20/%20macOS "Linux/macOS build status (Travis)")](https://travis-ci.org/status-im/nim-beacon-chain)
 [![Build Status (Azure)](https://dev.azure.com/nimbus-dev/nim-beacon-chain/_apis/build/status/status-im.nim-beacon-chain?branchName=master)](https://dev.azure.com/nimbus-dev/nim-beacon-chain/_build/latest?definitionId=3&branchName=master)
+[![Github Actions CI](https://github.com/status-im/nim-beacon-chain/workflows/Nimbus%20nim-beacon-chain%20CI/badge.svg)](https://github.com/status-im/nim-blscurve/actions?query=workflow%3A%22BLSCurve+CI%22)
 [![License: Apache](https://img.shields.io/badge/License-Apache%202.0-blue.svg)](https://opensource.org/licenses/Apache-2.0)
 [![License: MIT](https://img.shields.io/badge/License-MIT-blue.svg)](https://opensource.org/licenses/MIT)
 ![Stability: experimental](https://img.shields.io/badge/stability-experimental-orange.svg)
@@ -15,29 +16,31 @@ Nimbus beacon chain is a research implementation of the beacon chain component o
 <!-- DON'T EDIT THIS SECTION, INSTEAD RE-RUN doctoc TO UPDATE -->
 
 
-- [Documentation](#documentation)
-- [Related](#related)
-- [Prerequisites for everyone](#prerequisites-for-everyone)
-  - [Linux](#linux)
-  - [MacOS](#macos)
-  - [Windows](#windows)
-  - [Android](#android)
-- [For users](#for-users)
-  - [Connecting to testnets](#connecting-to-testnets)
-  - [Getting metrics from a local testnet client](#getting-metrics-from-a-local-testnet-client)
-- [Interop (for other Eth2 clients)](#interop-for-other-eth2-clients)
-- [For researchers](#for-researchers)
-  - [State transition simulation](#state-transition-simulation)
-  - [Local network simulation](#local-network-simulation)
-  - [Visualising simulation metrics](#visualising-simulation-metrics)
-  - [Network inspection](#network-inspection)
-- [For developers](#for-developers)
-  - [Windows dev environment](#windows-dev-environment)
-  - [Linux, MacOS](#linux-macos)
-  - [Raspberry Pi](#raspberry-pi)
-  - [Makefile tips and tricks for developers](#makefile-tips-and-tricks-for-developers)
-  - [CI setup](#ci-setup)
-- [License](#license)
+- [Nimbus Eth2 (Beacon Chain)](#nimbus-eth2-beacon-chain)
+  - [Documentation](#documentation)
+  - [Related projects](#related-projects)
+  - [Prerequisites for everyone](#prerequisites-for-everyone)
+    - [Linux](#linux)
+    - [MacOS](#macos)
+    - [Windows](#windows)
+    - [Android](#android)
+  - [For users](#for-users)
+    - [Connecting to testnets](#connecting-to-testnets)
+    - [Getting metrics from a local testnet client](#getting-metrics-from-a-local-testnet-client)
+    - [Stress-testing the client by limiting the CPU power](#stress-testing-the-client-by-limiting-the-cpu-power)
+  - [Interop (for other Eth2 clients)](#interop-for-other-eth2-clients)
+  - [For researchers](#for-researchers)
+    - [State transition simulation](#state-transition-simulation)
+    - [Local network simulation](#local-network-simulation)
+    - [Visualising simulation metrics](#visualising-simulation-metrics)
+    - [Network inspection](#network-inspection)
+  - [For developers](#for-developers)
+    - [Windows dev environment](#windows-dev-environment)
+    - [Linux, MacOS](#linux-macos)
+    - [Raspberry Pi](#raspberry-pi)
+    - [Makefile tips and tricks for developers](#makefile-tips-and-tricks-for-developers)
+    - [CI setup](#ci-setup)
+  - [License](#license)
 
 <!-- END doctoc generated TOC please keep comment here to allow auto update -->
 
diff --git a/config.nims b/config.nims
index aa6248707..a1fa9ffaf 100644
--- a/config.nims
+++ b/config.nims
@@ -30,7 +30,7 @@ else:
   if defined(windows):
     # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65782
     # ("-fno-asynchronous-unwind-tables" breaks Nim's exception raising, sometimes)
-    switch("passC", "-mno-avx512vl")
+    switch("passC", "-mno-avx512f")
 
 --threads:on
 --opt:speed
diff --git a/vendor/nimbus-build-system b/vendor/nimbus-build-system
index 41272d200..79469de15 160000
--- a/vendor/nimbus-build-system
+++ b/vendor/nimbus-build-system
@@ -1 +1 @@
-Subproject commit 41272d2002a46383265afe20881de8d849eafe01
+Subproject commit 79469de15653d40fc2751f984cf52d0ef6084e7a