diff --git a/eng/pipelines/common/global-build-job.yml b/eng/pipelines/common/global-build-job.yml
index f071c7f33afc31..964528ebecf2c7 100644
--- a/eng/pipelines/common/global-build-job.yml
+++ b/eng/pipelines/common/global-build-job.yml
@@ -21,7 +21,8 @@ parameters:
   shouldContinueOnError: false
   dependOnEvaluatePaths: false
   isOfficialBuild: false
-  buildingOnSourceBuildImage: false
+  isSourceBuild: false
+  isNonPortableSourceBuild: false
   runtimeFlavor: 'coreclr'
   runtimeVariant: ''
   helixQueues: ''
@@ -113,9 +114,9 @@ jobs:
           value: ''
 
       - name: _sclEnableCommand
-        ${{ if eq(parameters.buildingOnSourceBuildImage, true) }}:
+        ${{ if eq(parameters.isSourceBuild, true) }}:
           value: scl enable llvm-toolset-7.0 --
-        ${{ if ne(parameters.buildingOnSourceBuildImage, true) }}:
+        ${{ if ne(parameters.isSourceBuild, true) }}:
           value: ''
 
       - ${{ each variable in parameters.variables }}:
@@ -136,15 +137,15 @@ jobs:
           artifact: Mono_Offsets_${{monoCrossAOTTargetOS}}
           path: '$(Build.SourcesDirectory)/artifacts/obj/mono/offsetfiles'
 
-    - ${{ if eq(parameters.buildingOnSourceBuildImage, true) }}:
+    - ${{ if eq(parameters.isSourceBuild, true) }}:
       - template: /eng/common/templates/steps/source-build.yml
         parameters:
           platform:
             buildScript: $(_sclEnableCommand) $(Build.SourcesDirectory)$(dir)build$(scriptExt)
-            nonPortable: true
-            # Use a custom RID that isn't in the RID graph here to validate we don't break the usage of custom rids that aren't in the graph.
-            targetRID: banana.24-x64
+            nonPortable: ${{ parameters.isNonPortableSourceBuild }}
+            targetRID: ${{ parameters.targetRid }}
             runtimeOS: linux
+            name: ${{ parameters.platform }}
 
     - ${{ if in(parameters.osGroup, 'OSX', 'iOS', 'tvOS', 'MacCatalyst') }}:
       - script: $(Build.SourcesDirectory)/eng/install-native-dependencies.sh ${{ parameters.osGroup }} ${{ parameters.archType }} azDO
@@ -163,7 +164,7 @@ jobs:
           filePath: $(Build.SourcesDirectory)/eng/pipelines/mono/update-machine-certs.ps1
 
     # Build
-    - ${{ if eq(parameters.buildingOnSourceBuildImage, false) }}:
+    - ${{ if eq(parameters.isSourceBuild, false) }}:
       - script: $(_sclEnableCommand) $(Build.SourcesDirectory)$(dir)build$(scriptExt) -ci -arch ${{ parameters.archType }} $(_osParameter) ${{ parameters.buildArgs }} $(_officialBuildParameter) $(_crossBuildPropertyArg) $(_cxx11Parameter) $(_richCodeNavigationParam) $(_buildDarwinFrameworksParameter) $(_overrideTestScriptWindowsCmdParameter)
         displayName: Build product
         ${{ if eq(parameters.useContinueOnErrorDuringBuild, true) }}:
diff --git a/eng/pipelines/common/platform-matrix.yml b/eng/pipelines/common/platform-matrix.yml
index 1dca99ef9d58be..d66fa5c9f4a0f0 100644
--- a/eng/pipelines/common/platform-matrix.yml
+++ b/eng/pipelines/common/platform-matrix.yml
@@ -279,7 +279,57 @@ jobs:
         disableClrTest: true
         ${{ insert }}: ${{ parameters.jobParameters }}
 
-# Linux x64 Source Build
+# Centos 7 x64 Source Build
+
+- ${{ if containsValue(parameters.platforms, 'SourceBuild_Centos7_x64') }}:
+  - template: xplat-setup.yml
+    parameters:
+      jobTemplate: ${{ parameters.jobTemplate }}
+      helixQueuesTemplate: ${{ parameters.helixQueuesTemplate }}
+      variables: ${{ parameters.variables }}
+      osGroup: Linux
+      archType: x64
+      targetRid: centos.7-x64
+      platform: Centos7_Linux_x64
+      shouldContinueOnError: ${{ parameters.shouldContinueOnError }}
+      container:
+        image: centos-7-source-build-20210714125450-5d87b80
+        registry: mcr
+      jobParameters:
+        runtimeFlavor: ${{ parameters.runtimeFlavor }}
+        stagedBuild: ${{ parameters.stagedBuild }}
+        buildConfig: ${{ parameters.buildConfig }}
+        helixQueueGroup: ${{ parameters.helixQueueGroup }}
+        isSourceBuild: true
+        isNonPortableSourceBuild: true
+        ${{ insert }}: ${{ parameters.jobParameters }}
+
+# Non-existent RID Source Build
+
+- ${{ if containsValue(parameters.platforms, 'SourceBuild_Banana24_x64') }}:
+  - template: xplat-setup.yml
+    parameters:
+      jobTemplate: ${{ parameters.jobTemplate }}
+      helixQueuesTemplate: ${{ parameters.helixQueuesTemplate }}
+      variables: ${{ parameters.variables }}
+      osGroup: Linux
+      archType: x64
+      targetRid: banana.24-x64
+      platform: Banana24_Linux_x64
+      shouldContinueOnError: ${{ parameters.shouldContinueOnError }}
+      container:
+        image: centos-7-source-build-20210714125450-5d87b80
+        registry: mcr
+      jobParameters:
+        runtimeFlavor: ${{ parameters.runtimeFlavor }}
+        stagedBuild: ${{ parameters.stagedBuild }}
+        buildConfig: ${{ parameters.buildConfig }}
+        helixQueueGroup: ${{ parameters.helixQueueGroup }}
+        isSourceBuild: true
+        isNonPortableSourceBuild: true
+        ${{ insert }}: ${{ parameters.jobParameters }}
+
+# Portable Linux x64 Source Build
 
 - ${{ if containsValue(parameters.platforms, 'SourceBuild_Linux_x64') }}:
   - template: xplat-setup.yml
@@ -300,8 +350,9 @@ jobs:
         stagedBuild: ${{ parameters.stagedBuild }}
         buildConfig: ${{ parameters.buildConfig }}
         helixQueueGroup: ${{ parameters.helixQueueGroup }}
+        isSourceBuild: true
+        isNonPortableSourceBuild: false
         ${{ insert }}: ${{ parameters.jobParameters }}
-        buildingOnSourceBuildImage: true
 
 # Linux s390x
 
diff --git a/eng/pipelines/global-build.yml b/eng/pipelines/global-build.yml
index 2afd2f43bf037f..01f38d07b51f34 100644
--- a/eng/pipelines/global-build.yml
+++ b/eng/pipelines/global-build.yml
@@ -163,13 +163,11 @@ jobs:
 - template: /eng/pipelines/common/platform-matrix.yml
   parameters:
     jobTemplate: /eng/pipelines/common/global-build-job.yml
-    buildConfig: release
+    buildConfig: Release
     platforms:
     - SourceBuild_Linux_x64
     jobParameters:
-      nameSuffix: SourceBuild
-      timeoutInMinutes: 120
-      condition:
-        or(
-          eq(dependencies.evaluate_paths.outputs['SetPathVars_non_mono_and_wasm.containsChange'], true),
-          eq(variables['isRollingBuild'], true))
+      nameSuffix: PortableSourceBuild
+      extraStepsParameters:
+        name: SourceBuildPackages
+      timeoutInMinutes: 95
diff --git a/eng/pipelines/runtime-official.yml b/eng/pipelines/runtime-official.yml
index a837c870fbef93..5f5dfc6cef131c 100644
--- a/eng/pipelines/runtime-official.yml
+++ b/eng/pipelines/runtime-official.yml
@@ -364,9 +364,6 @@ stages:
         runTests: false
         useHelix: false
 
-  #
-  # Build Sourcebuild leg
-  #
   - template: /eng/pipelines/common/platform-matrix.yml
     parameters:
       jobTemplate: /eng/pipelines/common/global-build-job.yml
@@ -375,13 +372,12 @@ stages:
       platforms:
       - SourceBuild_Linux_x64
       jobParameters:
-        nameSuffix: SourceBuild
+        nameSuffix: PortableSourceBuild
         extraStepsTemplate: /eng/pipelines/common/upload-intermediate-artifacts-step.yml
         extraStepsParameters:
           name: SourceBuildPackages
         timeoutInMinutes: 95
 
-
   #
   # Installer Build
   #
diff --git a/eng/pipelines/runtime.yml b/eng/pipelines/runtime.yml
index 09b192f74b1efc..ec27c0b21b8a7c 100644
--- a/eng/pipelines/runtime.yml
+++ b/eng/pipelines/runtime.yml
@@ -1296,3 +1296,41 @@ jobs:
           eq(dependencies.evaluate_paths.outputs['SetPathVars_coreclr.containsChange'], true),
           eq(dependencies.evaluate_paths.outputs['SetPathVars_libraries.containsChange'], true),
           eq(variables['isRollingBuild'], true))
+
+#
+# Sourcebuild legs
+# We have 3 important legs for source-build:
+# - Centos.7 (ensures that RH keeps working)
+# - Linux-x64 portable (used for dependency flow and downstream PR verification)
+# - Banana.24 - Non-existent RID to ensure we don't break RIDs we don't know about.
+#
+# Running all of these everywhere is wasteful. Run Banana.24 and CentOS.7 in rolling CI,
+# Run Linux-x64 in PR.
+
+- template: /eng/pipelines/common/platform-matrix.yml
+  parameters:
+    jobTemplate: /eng/pipelines/common/global-build-job.yml
+    buildConfig: Release
+    helixQueueGroup: pr
+    platforms:
+    - SourceBuild_Centos7_x64
+    jobParameters:
+      nameSuffix: Centos7SourceBuild
+      extraStepsParameters:
+        name: SourceBuildPackages
+      timeoutInMinutes: 95
+      condition: eq(variables['isRollingBuild'], true)
+
+- template: /eng/pipelines/common/platform-matrix.yml
+  parameters:
+    jobTemplate: /eng/pipelines/common/global-build-job.yml
+    buildConfig: Debug
+    helixQueueGroup: pr
+    platforms:
+    - SourceBuild_Banana24_x64
+    jobParameters:
+      nameSuffix: Banana24SourceBuild
+      extraStepsParameters:
+        name: SourceBuildPackages
+      timeoutInMinutes: 95
+      condition: eq(variables['isRollingBuild'], true)