diff --git a/.github/workflows/header_checks.yml b/.github/workflows/header_checks.yml.bak
similarity index 100%
rename from .github/workflows/header_checks.yml
rename to .github/workflows/header_checks.yml.bak
diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml.bak
similarity index 100%
rename from .github/workflows/main.yml
rename to .github/workflows/main.yml.bak
diff --git a/.github/workflows/multiarch_checks.yml b/.github/workflows/multiarch_checks.yml
new file mode 100644
index 00000000000..b839e3e7272
--- /dev/null
+++ b/.github/workflows/multiarch_checks.yml
@@ -0,0 +1,76 @@
+name: Multiarch checks
+
+on:
+  pull_request:
+    branches: [ develop, master ]
+  push:
+    branches: [ develop, master ]
+    paths-ignore:
+      - 'doygen/**'
+      - 'hooks/**'
+      - 'licenses/**'
+      - 'LICENSE.md'
+      - 'README.md'
+      - 'RELEASE-NOTES.txt'
+
+permissions:
+  contents: read
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.head_ref || github.run_id }}
+  cancel-in-progress: true
+
+jobs:
+  multiarch-prim-rev:
+    name: ${{ matrix.config.platform }} ${{ matrix.config.batch }}
+    runs-on: ubuntu-latest
+
+    strategy:
+      fail-fast: false
+      matrix:
+        config:
+          - { platform: ppc64le, batch: 0}
+          - { platform: ppc64le, batch: 1}
+          - { platform: ppc64le, batch: 2}
+          - { platform: ppc64le, batch: 3}
+          - { platform: ppc64le, batch: 4}
+          - { platform: ppc64le, batch: 5}
+          - { platform: ppc64le, batch: 6}
+          - { platform: ppc64le, batch: 7}
+          - { platform: ppc64le, batch: 8}
+          - { platform: ppc64le, batch: 9}
+          - { platform: ppc64le, batch: 10}
+          - { platform: ppc64le, batch: 11}
+          - { platform: ppc64le, batch: 12}
+          - { platform: ppc64le, batch: 13}
+          - { platform: ppc64le, batch: 14}
+          - { platform: ppc64le, batch: 15}
+          - { platform: ppc64le, batch: 16}
+          - { platform: ppc64le, batch: 17}
+          - { platform: ppc64le, batch: 18}
+          - { platform: ppc64le, batch: 19}
+
+    steps:
+      - uses: actions/checkout@v3
+      - uses: docker/setup-qemu-action@v2
+      - uses: addnab/docker-run-action@v3
+        with:
+          image: debian:sid-slim
+          options: -v ${{ github.workspace }}:/work --platform linux/${{ matrix.config.platform }} -e DEBIAN_FRONTEND=noninteractive
+          run: |
+            apt-get update && apt-get install -y build-essential python-is-python3
+            cd /work
+            TargetTests=(test/unit/math/prim/*/*.cpp)
+            NTests=${#TargetTests[@]}
+            TestsPerBatch="$(($NTests / 20))"
+            StartOfBatch="$((${{ matrix.config.batch }} * $TestsPerBatch))"
+            # Compile and run in sub-batches of 5 to fail faster
+            echo "${TargetTests[@]}" | xargs -n 5 python ./runTests.py -j2
+          shell: bash
+
+      - name: Upload gtest_output xml
+        uses: actions/upload-artifact@v3
+        if: failure()
+        with:
+          name: gtest_outputs_xml
+          path: '**/*_test.xml'
diff --git a/Jenkinsfile b/Jenkinsfile.bak
similarity index 100%
rename from Jenkinsfile
rename to Jenkinsfile.bak
diff --git a/make/compiler_flags b/make/compiler_flags
index 1552381f232..d1ced2ab234 100644
--- a/make/compiler_flags
+++ b/make/compiler_flags
@@ -174,6 +174,9 @@ ifeq ($(OS),Darwin)
   ifeq (clang,$(CXX_TYPE))
     CXXFLAGS_OS ?= -Wno-unknown-warning-option -Wno-tautological-compare -Wno-sign-compare
   endif
+  ifeq (arm64, $(shell uname -m))
+    CXXFLAGS_OS += -ffp-contract=off
+  endif
 endif
 
 ifeq ($(OS),Linux)
@@ -190,6 +193,9 @@ ifeq ($(OS),Linux)
   ifeq (clang,$(CXX_TYPE))
     LDLIBS_OS ?= -lpthread
   endif
+  ifeq (aarch64, $(shell uname -m))
+    CXXFLAGS_OS += -ffp-contract=off
+  endif
 endif
 
 ## makes reentrant version lgamma_r available from cmath
diff --git a/test/unit/math/prim/fun/offset_multiplier_transform_test.cpp b/test/unit/math/prim/fun/offset_multiplier_transform_test.cpp
index a17b98b9023..52390060d69 100644
--- a/test/unit/math/prim/fun/offset_multiplier_transform_test.cpp
+++ b/test/unit/math/prim/fun/offset_multiplier_transform_test.cpp
@@ -159,7 +159,7 @@ TEST(prob_transform, offset_multiplier_constrain_matrix) {
       EXPECT_FLOAT_EQ(result(i), stan::math::offset_multiplier_constrain(
                                      x(i), offsetd, sigmad, lp1));
     }
-    EXPECT_EQ(lp0, lp1);
+    EXPECT_FLOAT_EQ(lp0, lp1);
     auto x_free = stan::math::offset_multiplier_free(result, offsetd, sigmad);
     for (size_t i = 0; i < x.size(); ++i) {
       EXPECT_FLOAT_EQ(x.coeff(i), x_free.coeff(i));
@@ -193,7 +193,7 @@ TEST(prob_transform, offset_multiplier_constrain_matrix) {
       EXPECT_FLOAT_EQ(result(i), stan::math::offset_multiplier_constrain(
                                      x(i), offsetd, sigma(i), lp1));
     }
-    EXPECT_EQ(lp0, lp1);
+    EXPECT_FLOAT_EQ(lp0, lp1);
     auto x_free = stan::math::offset_multiplier_free(result, offsetd, sigma);
     for (size_t i = 0; i < x.size(); ++i) {
       EXPECT_FLOAT_EQ(x.coeff(i), x_free.coeff(i));
@@ -211,7 +211,7 @@ TEST(prob_transform, offset_multiplier_constrain_matrix) {
       EXPECT_FLOAT_EQ(result(i), stan::math::offset_multiplier_constrain(
                                      x(i), offset(i), sigma(i), lp1));
     }
-    EXPECT_EQ(lp0, lp1);
+    EXPECT_FLOAT_EQ(lp0, lp1);
     auto x_free = stan::math::offset_multiplier_free(result, offset, sigma);
     for (size_t i = 0; i < x.size(); ++i) {
       EXPECT_FLOAT_EQ(x.coeff(i), x_free.coeff(i));
diff --git a/test/unit/math/prim/prob/neg_binomial_test.cpp b/test/unit/math/prim/prob/neg_binomial_test.cpp
index ac5b0f611cb..5d9d091f002 100644
--- a/test/unit/math/prim/prob/neg_binomial_test.cpp
+++ b/test/unit/math/prim/prob/neg_binomial_test.cpp
@@ -189,8 +189,10 @@ TEST(ProbDistributionsNegBinomial, chiSquareGoodnessFitTest3) {
 
   double chi = 0;
 
-  for (int j = 0; j < K; j++)
+  for (int j = 0; j < K; j++) {
+    if (expect[j] == 0) { continue; }
     chi += ((bin[j] - expect[j]) * (bin[j] - expect[j]) / expect[j]);
+  }
 
   EXPECT_LT(chi, boost::math::quantile(boost::math::complement(mydist, 1e-6)));
 }