diff --git a/artiq-fast/artiq-board.nix b/artiq-fast/artiq-board.nix
index ac591af..69ae67c 100644
--- a/artiq-fast/artiq-board.nix
+++ b/artiq-fast/artiq-board.nix
@@ -6,6 +6,7 @@
 }:
 
 let
+  version = import ./pkgs/artiq-version.nix (with pkgs; { inherit stdenv fetchgit git; });
   artiqSrc = import ./pkgs/artiq-src.nix { fetchgit = pkgs.fetchgit; };
   artiqpkgs = import ./default.nix { inherit pkgs; };
   fetchcargo = import ./fetchcargo.nix {
@@ -41,59 +42,112 @@ let
       cp -R * $out/registry
       '';
   };
-
 in
 { target
 , variant
 , src ? null
 , buildCommand ? "python -m artiq.gateware.targets.${target} -V ${variant}"
 , extraInstallCommands ? ""}:
-
-# Board packages are Python modules so that they get added to the ARTIQ Python
-# environment, and artiq_flash finds them.
-pkgs.python3Packages.toPythonModule (pkgs.stdenv.mkDerivation rec {
+let
   name = "artiq-board-${target}-${variant}-${version}";
-  version = import ./pkgs/artiq-version.nix (with pkgs; { inherit stdenv fetchgit git; });
-  inherit src;
-  phases = [ "buildPhase" "installCheckPhase" "installPhase" "checkPhase" ];
-  nativeBuildInputs = [
-    vivado
-    pkgs.gnumake
-    artiqpkgs.cargo
-    artiqpkgs.rustc
-    artiqpkgs.binutils-or1k
-    artiqpkgs.llvm-or1k
-  ];
-  buildInputs = [ (pkgs.python3.withPackages(ps: with ps; [ jinja2 numpy artiqpkgs.migen artiqpkgs.microscope artiqpkgs.misoc artiqpkgs.jesd204b artiqpkgs.artiq ])) ];
-  buildPhase = 
-    ''
-    export CARGO_HOME=${cargoVendored}
-    export TARGET_AR=or1k-linux-ar
-    ${buildCommand}
+  installPath = "${pkgs.python3Packages.python.sitePackages}/artiq/board-support/${target}-${variant}";
+
+  boardModule = 
+    # Board packages are Python modules so that they get added to the ARTIQ Python
+    # environment, and artiq_flash finds them.
+    pkgs.python3Packages.toPythonModule (pkgs.stdenv.mkDerivation {
+      name = "${name}-firmware";
+      inherit version src;
+      phases = [ "buildPhase" "installCheckPhase" "installPhase" "checkPhase" ];
+      nativeBuildInputs = [
+        vivado
+        pkgs.gnumake pkgs.which
+        artiqpkgs.cargo
+        artiqpkgs.rustc
+        artiqpkgs.binutils-or1k
+        artiqpkgs.llvm-or1k
+      ];
+      buildInputs = [
+        (pkgs.python3.withPackages(ps: with ps; [ jinja2 numpy artiqpkgs.migen artiqpkgs.microscope artiqpkgs.misoc artiqpkgs.jesd204b artiqpkgs.artiq ]))
+      ];
+      buildPhase =
+        ''
+        export CARGO_HOME=${cargoVendored}
+        export TARGET_AR=or1k-linux-ar
+        ${buildCommand} --no-compile-gateware
+        '';
+      installPhase =
+        ''
+        TARGET_DIR=$out/${installPath}
+        mkdir -p $TARGET_DIR $out/src
+
+        cp -ar artiq_${target}/${variant}/gateware $out/src/
+
+        if [ -e artiq_${target}/${variant}/software/bootloader/bootloader.bin ]
+        then cp artiq_${target}/${variant}/software/bootloader/bootloader.bin $TARGET_DIR
+        fi
+        if [ -e artiq_${target}/${variant}/software/runtime ]
+        then cp artiq_${target}/${variant}/software/runtime/runtime.{elf,fbi} $TARGET_DIR
+        else cp artiq_${target}/${variant}/software/satman/satman.{elf,fbi} $TARGET_DIR
+        fi
+        ${extraInstallCommands}
+        '';
+    });
+
+  vivadoInputArchive = pkgs.stdenv.mkDerivation {
+    name = "${name}-vivado-input.nar.base64";
+    buildInputs = [ pkgs.nix ];
+    phases = [ "installPhase" ];
+    installPhase = "nix-store --dump ${boardModule}/src/gateware | base64 -w0 > $out";
+  };
+
+  # Funnelling the source code through a Nix string allows dropping
+  # all dependencies via `unsafeDiscardStringContext`. The gateware
+  # will then be rebuilt only when these contents have changed.
+  pureVivadoInputArchive = builtins.toFile "${name}-vivado-input.nar.base64" (
+    builtins.unsafeDiscardStringContext (
+      builtins.readFile vivadoInputArchive
+    ));
+
+  # Depends on just Vivado and the generated Bitstream source
+  vivadoOutput = pkgs.stdenvNoCC.mkDerivation {
+    name = builtins.unsafeDiscardStringContext "${name}-vivado-output";
+
+    unpackPhase = "base64 -d < ${pureVivadoInputArchive} | nix-store --restore gateware";
+    buildInputs = [ vivado pkgs.nix ];
+    buildPhase = ''
+      cd gateware
+      vivado -mode batch -source top.tcl
     '';
-  # temporarily disabled because there is currently always at least one Kasli bitstream
-  # that fails timing and blocks the conda channel.
-  doCheck = false;
-  checkPhase = ''
-    # Search for PCREs in the Vivado output to check for errors
-    check_log() {
-      grep -Pe "$1" artiq_${target}/${variant}/gateware/vivado.log && exit 1 || true
-    }
-    check_log "\d+ constraint not met\."
-    check_log "Timing constraints are not met\."
+
+    installPhase = ''
+      TARGET_DIR=$out/${builtins.unsafeDiscardStringContext installPath}
+      mkdir -p $TARGET_DIR
+
+      chmod a+r top.bit
+      cp top.bit $TARGET_DIR
     '';
-  installPhase =
-    ''
-    TARGET_DIR=$out/${pkgs.python3Packages.python.sitePackages}/artiq/board-support/${target}-${variant}
-    mkdir -p $TARGET_DIR
-    cp artiq_${target}/${variant}/gateware/top.bit $TARGET_DIR
-    if [ -e artiq_${target}/${variant}/software/bootloader/bootloader.bin ]
-    then cp artiq_${target}/${variant}/software/bootloader/bootloader.bin $TARGET_DIR
-    fi
-    if [ -e artiq_${target}/${variant}/software/runtime ]
-    then cp artiq_${target}/${variant}/software/runtime/runtime.{elf,fbi} $TARGET_DIR
-    else cp artiq_${target}/${variant}/software/satman/satman.{elf,fbi} $TARGET_DIR
-    fi
-    ${extraInstallCommands}
+
+    # temporarily disabled because there is currently always at least one Kasli bitstream
+    # that fails timing and blocks the conda channel.
+    doCheck = false;
+    checkPhase = ''
+      # Search for PCREs in the Vivado output to check for errors
+      check_log() {
+        set +e
+        grep -Pe "$1" vivado.log
+        FOUND=$?
+        set -e
+        if [ $FOUND != 1 ]; then
+          exit 1
+        fi
+      }
+      check_log "\d+ constraint not met\."
+      check_log "Timing constraints are not met\."
     '';
-})
+  };
+in pkgs.buildEnv rec {
+  inherit name;
+  paths = [ boardModule vivadoOutput ];
+  pathsToLink = [ "/${installPath}" ];
+}