diff --git a/.github/workflows/linux.yml b/.github/workflows/linux.yml
index 338b6bf..38af9ec 100644
--- a/.github/workflows/linux.yml
+++ b/.github/workflows/linux.yml
@@ -9,7 +9,7 @@ on:
 jobs:
   gnat_gprbuild:
     name: GNAT Linux and GPRbuild
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-20.04-64cores
     steps:
     - name: Checkout Project
       uses: actions/checkout@v2
@@ -63,7 +63,7 @@ jobs:
   gnatcov:
     name: GNATcov
     needs: gnat_gprbuild
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-20.04-64cores
     steps:
     - name: Checkout Project
       uses: actions/checkout@v2
@@ -105,7 +105,7 @@ jobs:
         target: ["arm-elf", "riscv64-elf", "avr-elf"]
     name: GNAT ${{ matrix.target }}-linux
     needs: gnat_gprbuild
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-20.04-64cores
     steps:
     - name: Checkout Project
       uses: actions/checkout@v2
@@ -214,7 +214,7 @@ jobs:
   spark:
     name: spark
     needs: [why3, alt_ergo]
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-20.04-64cores
     steps:
     - name: Checkout Project
       uses: actions/checkout@v2
diff --git a/.github/workflows/windows.yml b/.github/workflows/windows.yml
index 92de1fb..d5323c5 100644
--- a/.github/workflows/windows.yml
+++ b/.github/workflows/windows.yml
@@ -8,7 +8,7 @@ on:
 jobs:
   gnat_gprbuild:
     name: GNAT Windows and gprbuild
-    runs-on: windows-2019
+    runs-on: windows-2019-64cores
     env:
       CONFIG_SHELL: /bin/bash
     defaults:
@@ -74,7 +74,7 @@ jobs:
   gnatcov:
     name: GNATcov
     needs: gnat_gprbuild
-    runs-on: windows-2019
+    runs-on: windows-2019-64cores
     env:
       CONFIG_SHELL: /bin/bash
     defaults:
@@ -135,7 +135,7 @@ jobs:
         target: ["arm-elf", "riscv64-elf", "avr-elf"]
     name: GNAT ${{ matrix.target }}-windows
     needs: gnat_gprbuild
-    runs-on: windows-2019
+    runs-on: windows-2019-64cores
     env:
       CONFIG_SHELL: /bin/bash
     defaults:
@@ -194,7 +194,7 @@ jobs:
       matrix:
         ocaml-compiler:
           - 4.11.2
-    runs-on: windows-2019
+    runs-on: windows-2019-64cores
     steps:
       - name: Checkout code
         uses: actions/checkout@v2
@@ -259,7 +259,7 @@ jobs:
   spark:
     name: spark
     needs: [why3, alt_ergo]
-    runs-on: windows-2019
+    runs-on: windows-2019-64cores
     env:
       CONFIG_SHELL: /bin/bash
     defaults:
diff --git a/specs/gcc.anod b/specs/gcc.anod
index ec35abd..1abb944 100644
--- a/specs/gcc.anod
+++ b/specs/gcc.anod
@@ -1,4 +1,4 @@
-from e3.os.fs import unixpath
+from e3.os.fs import unixpath, cd
 from e3.fs import cp, mkdir, sync_tree
 from e3.anod.helper import Configure, Make
 from e3.anod.spec import Anod
@@ -81,9 +81,6 @@ class GCC(spec("gh-artifact")):
         else:
             deps.append(Anod.Dependency("base_gcc", host="build", target="host"))
 
-        if self.env.build.os.name != "darwin":
-            deps.append(Anod.Dependency("isl", host="build", target="host"))
-
         if self.env.target.os.name != "darwin":
             deps.append(Anod.Dependency("binutils", target="target"))
 
@@ -190,6 +187,10 @@ class GCC(spec("gh-artifact")):
             "lib", "gcc", self.env.target.triplet, self.version
         )
 
+        cd(self["SRC_DIR"])
+        self.shell(os.path.join(self['SRC_DIR'], 'contrib', 'download_prerequisites'))
+        cd(self["BUILD_DIR"])
+
         if self.env.target.os.name == "windows":
             # Deploy the mingw dependency in the ./mingw64 directory
             self.deps["mingw"].merge(os.path.join(self["SRC_DIR"], "mingw64"))
@@ -238,12 +239,6 @@ class GCC(spec("gh-artifact")):
         for a in self.configure_args():
             configure.add(a)
 
-        for m in ("mpfr", "gmp", "mpc", "isl"):
-            if m in self.deps:
-                configure.add(
-                    "--with-%s=%s" % (m, unixpath(self.deps[m]["INSTALL_DIR"]))
-                )
-
         if self.env.host.os.name == "windows":
             # https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=902c755930326cb4405672aa3ea13c35c653cbff
             os.environ["CPPFLAGS"] = "-DCOM_NO_WINDOWS_H"