diff --git a/artiq-fast/artiq-board-legacy.nix b/artiq-fast/artiq-board-legacy.nix
new file mode 100644
index 0000000..ac591af
--- /dev/null
+++ b/artiq-fast/artiq-board-legacy.nix
@@ -0,0 +1,99 @@
+# Install Vivado in /opt and add to /etc/nixos/configuration.nix:
+#  nix.sandboxPaths = ["/opt"];
+
+{ pkgs
+, vivado ? import ./vivado.nix { inherit pkgs; }
+}:
+
+let
+  artiqSrc = import ./pkgs/artiq-src.nix { fetchgit = pkgs.fetchgit; };
+  artiqpkgs = import ./default.nix { inherit pkgs; };
+  fetchcargo = import ./fetchcargo.nix {
+    inherit (pkgs) stdenv cacert git;
+    inherit (artiqpkgs) cargo cargo-vendor;
+  };
+  cargoDeps = fetchcargo rec {
+    name = "artiq-firmware-cargo-deps";
+    src = "${artiqSrc}/artiq/firmware";
+    sha256 = (import "${artiqSrc}/artiq/firmware/cargosha256.nix");
+  };
+
+  cargoVendored = pkgs.stdenv.mkDerivation {
+    name = "artiq-firmware-cargo-vendored";
+    src = cargoDeps;
+    phases = [ "unpackPhase" "installPhase" ];
+    installPhase =
+      ''
+      mkdir -p $out/registry
+      cat << EOF > $out/config
+        [source.crates-io]
+        registry = "https://github.com/rust-lang/crates.io-index"
+        replace-with = "vendored-sources"
+
+        [source."https://github.com/m-labs/libfringe"]
+        git = "https://github.com/m-labs/libfringe"
+        rev = "b8a6d8f"
+        replace-with = "vendored-sources"
+
+        [source.vendored-sources]
+        directory = "$out/registry"
+      EOF
+      cp -R * $out/registry
+      '';
+  };
+
+in
+{ target
+, variant
+, src ? null
+, buildCommand ? "python -m artiq.gateware.targets.${target} -V ${variant}"
+, extraInstallCommands ? ""}:
+
+# Board packages are Python modules so that they get added to the ARTIQ Python
+# environment, and artiq_flash finds them.
+pkgs.python3Packages.toPythonModule (pkgs.stdenv.mkDerivation rec {
+  name = "artiq-board-${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}
+    '';
+  # 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/${pkgs.python3Packages.python.sitePackages}/artiq/board-support/${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}
+    '';
+})
diff --git a/artiq-fast/artiq-board.nix b/artiq-fast/artiq-board.nix
index ac591af..7850c4d 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 +42,147 @@ 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.stdenv.mkDerivation {
+      name = "${name}-firmware";
+      inherit version src;
+      phases = [ "buildPhase" "installCheckPhase" "installPhase" "checkPhase" ];
+      nativeBuildInputs = [
+        pkgs.gnumake pkgs.which
+        artiqpkgs.cargo
+        artiqpkgs.rustc
+        artiqpkgs.binutils-or1k
+        artiqpkgs.llvm-or1k
+      ];
+      buildInputs = [
+        (pkgs.python3.withPackages(ps: with ps; [ jinja2 numpy artiqpkgs.migen artiqpkgs.microscope artiqpkgs.misoc artiqpkgs.jesd204b artiqpkgs.artiq ]))
+      ];
+      buildPhase =
+        ''
+        export CARGO_HOME=${cargoVendored}
+        export TARGET_AR=or1k-linux-ar
+        ${buildCommand} --no-compile-gateware --gateware-identifier-str=unprogrammed
+        '';
+      installPhase =
+        ''
+        TARGET_DIR=$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
+        ${extraInstallCommands}
+        '';
+    };
+
+  identifierStr = "${version};${variant}";
+  identifiers = import (
+    pkgs.runCommandLocal "${name}-identifiers.nix" {
+      buildInputs = [ pkgs.python3 ];
+    } ''python ${./generate-identifier.py} "${identifierStr}" > $out''
+  );
+
+  vivadoInputArchive = pkgs.stdenv.mkDerivation {
+    name = "${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
+  vivadoCheckpoint = pkgs.stdenvNoCC.mkDerivation {
+    name = builtins.unsafeDiscardStringContext "${name}-vivado-checkpoint";
+
+    unpackPhase = "base64 -d < ${pureVivadoInputArchive} | nix-store --restore gateware";
+    buildInputs = [ vivado pkgs.nix ];
+    buildPhase = ''
+      cd gateware
+      vivado -mode batch -source top_route.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 = ''
+      mkdir -p $out
+
+      chmod a+r top_route.dcp
+      cp top_route.dcp $out
+      cp top_bitstream.tcl $out
     '';
-  installPhase =
-    ''
-    TARGET_DIR=$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
-    ${extraInstallCommands}
+  };
+
+  vivadoOutput = pkgs.stdenvNoCC.mkDerivation {
+    name = builtins.unsafeDiscardStringContext "${name}-vivado-output";
+    src = vivadoCheckpoint;
+    buildInputs = [ vivado ];
+    buildPhase =
+      ''
+      cat >top.tcl <<EOF
+      open_checkpoint top_route.dcp
+      '' +
+      (pkgs.lib.concatMapStrings ({ cell, init }:
+        ''
+        set_property INIT ${init} [get_cell ${cell}]
+        ''
+      ) identifiers) +
+      ''
+      source "top_bitstream.tcl"
+      EOF
+      vivado -mode batch -source top.tcl
+      '';
+    installPhase = ''
+      TARGET_DIR=$out/${builtins.unsafeDiscardStringContext installPath}
+      mkdir -p $TARGET_DIR
+      chmod a+r top.bit
+      cp top.bit $TARGET_DIR/
     '';
-})
+
+    # 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 [ $FOUND != 1 ]; then
+          exit 1
+        fi
+      }
+      check_log "\d+ constraint not met\."
+      check_log "Timing constraints are not met\."
+    '';
+  };
+in
+pkgs.python3Packages.toPythonModule (
+  pkgs.buildEnv rec {
+    inherit name;
+    paths = [ boardModule vivadoOutput ];
+    pathsToLink = [ "/${installPath}" ];
+  })
diff --git a/artiq-fast/default.nix b/artiq-fast/default.nix
index 91ec860..e11a097 100644
--- a/artiq-fast/default.nix
+++ b/artiq-fast/default.nix
@@ -10,7 +10,11 @@ let
   ];
   boardPackages = pkgs.lib.lists.foldr (board: start:
     let
-      boardBinaries = import ./artiq-board.nix { inherit pkgs; } {
+      packageImport =
+        if artiq6
+        then ./artiq-board.nix
+        else ./artiq-board-legacy.nix;
+      boardBinaries = import packageImport { inherit pkgs; } {
         target = board.target;
         variant = board.variant;
       };
diff --git a/artiq-fast/generate-identifier.py b/artiq-fast/generate-identifier.py
new file mode 100755
index 0000000..942505b
--- /dev/null
+++ b/artiq-fast/generate-identifier.py
@@ -0,0 +1,24 @@
+#!/usr/bin/env python
+#
+# Encodes data like ARTIQ build_soc.py ReprogrammableIdentifier
+
+import sys
+
+if len(sys.argv) != 2:
+    raise ValueError('argument missing')
+
+identifier_str = sys.argv[1]
+contents = list(identifier_str.encode())
+l = len(contents)
+if l > 255:
+    raise ValueError("Identifier string must be 255 characters or less")
+contents.insert(0, l)
+
+f = sys.stdout
+f.write("[\n");
+for i in range(7):
+    init = sum(1 << j if c & (1 << i) else 0 for j, c in enumerate(contents))
+    f.write(
+        '  {{ cell = "identifier_str{}"; init = "256\'h{:X}"; }}\n'.format(i, init)
+    )
+f.write("]\n");
diff --git a/artiq-full.nix b/artiq-full.nix
index d5ae0a5..ca52548 100644
--- a/artiq-full.nix
+++ b/artiq-full.nix
@@ -108,7 +108,11 @@ let
       ]);
 
       vivado = import ./fast/vivado.nix { inherit pkgs; };
-      artiq-board = import ./fast/artiq-board.nix { inherit pkgs vivado; };
+      artiq-board-import =
+        if pkgs.lib.strings.versionAtLeast artiq-fast.artiq.version "6.0"
+        then ./fast/artiq-board.nix
+        else ./fast/artiq-board-legacy.nix;
+      artiq-board = import artiq-board-import { inherit pkgs vivado; };
       conda-artiq-board = import ./conda-artiq-board.nix { inherit pkgs; };
       src = pkgs.fetchgit {
         url = "https://git.m-labs.hk/M-Labs/sinara-systems.git";