diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 445f190627..ccd31508ab 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -23,7 +23,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: [3.9]
+        python-version: ['3.10']
 
         name: [
           windows-2019-cl,
diff --git a/.github/workflows/conda-dev.yml b/.github/workflows/conda-dev.yml
index 912d5f31f0..8d1539c56a 100644
--- a/.github/workflows/conda-dev.yml
+++ b/.github/workflows/conda-dev.yml
@@ -16,7 +16,7 @@ jobs:
       fail-fast: false
       matrix:
         os: ['ubuntu-22.04', 'ubuntu-20.04', 'macOS-11', 'windows-2019']
-        python-version: ['3.9']
+        python-version: ['3.11']
         use_namespace: [false, true]
         include:
           - os: 'ubuntu-22.04'
diff --git a/tox.ini b/tox.ini
index 2a1d18bc1f..3f5c459c61 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,10 +1,11 @@
 [tox]
-envlist = py3{6,7,8,9}-build
+envlist = py3{7,8,9,10,11}-build
 skip_missing_interpreters = true
 skipsdist = true
 
 [base]
 setenv =
+    CPUS={env:CPUS:4}
     {abc,demo,soname,tests}: CFLAGS={env:CFLAGS:-march=native -O2 -g -DNDEBUG}
     {abc,demo,soname,tests}: CXXFLAGS={env:CXXFLAGS:-march=native -O2 -g -DNDEBUG}
     {abc,demo,soname,tests}: LDFLAGS={env:LDFLAGS:-march=native -O2 -g -DNDEBUG}
@@ -66,9 +67,9 @@ commands_pre =
     {base,build,clang}: cmake -E make_directory {toxinidir}/build
 
 commands =
-    abc: make -j4 ABC_USE_PIC=1 {posargs} abc
-    abc: make -j4 {posargs} libabc.a
-    soname: make -j4 ABC_USE_PIC=1 ABC_USE_SONAME=1 {posargs} lib
+    abc: make -j{env:CPUS} ABC_USE_PIC=1 {posargs} abc
+    abc: make -j{env:CPUS} {posargs} libabc.a
+    soname: make -j{env:CPUS} ABC_USE_PIC=1 ABC_USE_SONAME=1 {posargs} lib
     tests: make test
     # demo requires CC, CXX set in environment or on cmd line
     # eg:  CC=gcc CXX=g++ tox -e demo
@@ -76,22 +77,22 @@ commands =
     demo: bash -c '$CXX -o demo demo.o libabc.a -lm -ldl -lreadline -lpthread'
     demo: bash -c './demo i10.aig'
     {abc,soname,tests}: bash -c 'ls -lh *abc* demo || true'
-    base: bash -c 'cmake -G {posargs:"Ninja"} -DABC_USE_NAMESPACE=$ABC_USE_NAMESPACE -DCMAKE_INSTALL_PREFIX=$PREFIX ..'
-    base: bash -c 'cmake --build . --target install -j $(nproc)'
-    build: bash -c 'cmake -G {posargs:"Unix Makefiles"} -DCMAKE_BUILD_TYPE=$BUILD_TYPE -DABC_USE_NAMESPACE=$ABC_USE_NAMESPACE -DABC_ENABLE_LTO=ON -DBUILD_SHARED_LIBS=ON -DABC_USE_SONAME=$ABC_USE_SONAME -DCMAKE_INSTALL_PREFIX=$PREFIX ..'
-    clang: bash -c 'cmake -G {posargs:"Unix Makefiles"} -DCMAKE_BUILD_TYPE=$BUILD_TYPE -DABC_USE_NAMESPACE=$ABC_USE_NAMESPACE -DCOVERAGE_BUILD=ON -DBUILD_SHARED_LIBS=OFF ..'
-    {build}: bash -c 'cmake --build . -j $(nproc)'
-    {clang}: bash -c 'cmake --build . --target coverage -j $(nproc)'
-    {build,clang}: bash -c 'ctest -V -C $BUILD_TYPE --test-dir ./'
+    base: cmake -G {posargs:"Ninja"} -DABC_USE_NAMESPACE=$ABC_USE_NAMESPACE -DCMAKE_INSTALL_PREFIX={env:PREFIX} ..
+    base: cmake --build . --target install -j {env:CPUS}
+    build: cmake -G {posargs:"Unix Makefiles"} -DCMAKE_BUILD_TYPE=$BUILD_TYPE -DABC_USE_NAMESPACE=$ABC_USE_NAMESPACE -DABC_ENABLE_LTO=ON -DBUILD_SHARED_LIBS=ON -DABC_USE_SONAME=$ABC_USE_SONAME -DCMAKE_INSTALL_PREFIX={env:PREFIX} ..
+    clang: cmake -G {posargs:"Unix Makefiles"} -DCMAKE_BUILD_TYPE=$BUILD_TYPE -DABC_USE_NAMESPACE=$ABC_USE_NAMESPACE -DCOVERAGE_BUILD=ON -DBUILD_SHARED_LIBS=OFF ..
+    {build}: cmake --build . -j {env:CPUS}
+    {clang}: cmake --build . --target coverage -j {env:CPUS}
+    {build,clang}: ctest -V -C {env:BUILD_TYPE} --test-dir ./
     clang: lcov_cobertura build/coverage/lcov.info --base-dir {toxinidir}/src --output coverage.xml
     {base,build}: cmake --build . --target install
     {base,build}: bash -c 'find $PREFIX/ -type f -name \*abc\* -o -name demo | xargs ls -lh'
-    ctest: bash -c 'ctest -j $(nproc) --build-generator {posargs:"Ninja"} --build-and-test . build --build-options -DABC_USE_NAMESPACE=$ABC_USE_NAMESPACE -DABC_SKIP_EXE=ON -DCMAKE_BUILD_TYPE=$BUILD_TYPE --test-command ctest --rerun-failed --output-on-failure -V'
+    ctest: ctest -j {env:CPUS} --build-generator {posargs:"Ninja"} --build-and-test . build --build-options -DABC_USE_NAMESPACE=$ABC_USE_NAMESPACE -DABC_SKIP_EXE=ON -DCMAKE_BUILD_TYPE=$BUILD_TYPE --test-command ctest --rerun-failed --output-on-failure -V
     ctestwin: ctest --build-generator {posargs:"Visual Studio 16 2019"} --build-and-test . build --build-options -DBUILD_SHARED_LIBS=ON -DABC_USE_NO_PTHREADS=ON -DABC_USE_NO_READLINE=ON -DCMAKE_BUILD_TYPE={env:BUILD_TYPE} --test-command ctest --rerun-failed --output-on-failure -V
     ctest: bash -c 'ls -lh build/base_test build/libabc.* || true'
     lint: bash -c 'cpplint --output=gsed {toxinidir}/src/base/main/* {toxinidir}/lib/*'
     grind: bash -c 'cmake -G {posargs:"Ninja"} -S . -B build -DCMAKE_BUILD_TYPE=Debug'
-    grind: bash -c 'cmake --build build --target abc -j $(nproc)'
+    grind: bash -c 'cmake --build build --target abc -j $CPUS'
     grind: bash -c 'valgrind --tool=memcheck --xml=yes --xml-file=abc_check.xml --leak-check=full --show-leak-kinds=definite,possible --error-exitcode=127 ./build/src/base/main/abc "-c" "r i10.aig; b; ps; b; rw -l; rw -lz; b; rw -lz; b; ps; cec"'
     grind: valgrind-ci abc_check.xml --number-of-errors
     grind: valgrind-ci abc_check.xml --summary