diff --git a/SConscript b/SConscript
index 49f06af7d..3e607caa4 100644
--- a/SConscript
+++ b/SConscript
@@ -320,6 +320,11 @@ syscall_emulation_sources = Split('''
 	sim/syscall_emul.cc
         ''')
 
+# The following stuff (targetarch code and global define of THE_ISA)
+# are legacy things that assume we're only compiling one ISA at a
+# time.  These will have to go away if we want to build a binary that
+# supports multiple ISAs.
+
 targetarch_files = Split('''
         alpha_linux_process.hh
         alpha_memory.hh
@@ -338,18 +343,14 @@ for f in targetarch_files:
     env.Command('targetarch/' + f, 'arch/%s/%s' % (env['TARGET_ISA'], f),
                 '''echo '#include "arch/%s/%s"' > $TARGET''' % (env['TARGET_ISA'], f))
 
-# Let the target architecture define what sources it needs
-arch_source = SConscript('arch/%s/SConscript' % env['TARGET_ISA'],
-	build_dir = 'build/%s/' % env['BUILD_DIR'],
-	exports = 'env', duplicate = False)
-
 # Add a flag defining what THE_ISA should be for all compilation
 env.Append(CPPDEFINES=[('THE_ISA','%s_ISA' % env['TARGET_ISA'].upper())])
 
-SConscript('arch/SConscript', exports = 'env', duplicate = False)
+arch_sources = SConscript('arch/SConscript',
+                          exports = 'env', duplicate = False)
 
 # Set up complete list of sources based on configuration.
-sources = base_sources + arch_source
+sources = base_sources + arch_sources
 
 if env['FULL_SYSTEM']:
     sources += full_system_sources
@@ -364,27 +365,6 @@ if env['USE_MYSQL']:
 for opt in env.ExportOptions:
     env.ConfigFile(opt)
 
-###################################################
-#
-# Add an SCons scanner for ISA files
-#
-###################################################
-import SCons.Scanner
-
-def ISAScan():
-   return SCons.Scanner.Classic("ISAScan",
-                                "$ISASUFFIXES",
-                                "SRCDIR",
-                                '^[ \t]*##[ \t]*include[ \t]*"([^>"]+)"')
-
-def ISAPath(env, dir, target=None, source=None, a=None):
-   return (Dir(env['SRCDIR']), Dir('.'))   
-
-iscan = Scanner(function = ISAScan().scan, skeys = [".isa", ".ISA"],
-                path_function = ISAPath)
-env.Append(SCANNERS = iscan)
-
- 
 ###################################################
 #
 # Special build rules.
@@ -397,27 +377,6 @@ env.Command(Split('base/traceflags.hh base/traceflags.cc'),
             'base/traceflags.py',
             'python $SOURCE $TARGET.base')
 
-# several files are generated from arch/$TARGET_ISA/isa_desc.
-env.Command(Split('''
-	arch/%s/decoder.cc
-	arch/%s/decoder.hh
-        arch/%s/alpha_o3_exec.cc
-	arch/%s/fast_cpu_exec.cc
-        arch/%s/simple_cpu_exec.cc
-        arch/%s/full_cpu_exec.cc''' %
-	(env['TARGET_ISA'],
-	env['TARGET_ISA'],
-	env['TARGET_ISA'],
-	env['TARGET_ISA'],
-	env['TARGET_ISA'],
-	env['TARGET_ISA'])),
-	Split('''
-	arch/%s/isa/main.isa
-	arch/isa_parser.py''' %
-	env['TARGET_ISA']),
-	'$SRCDIR/arch/isa_parser.py $SOURCE $TARGET.dir arch/%s' % env['TARGET_ISA'])
-
-
 # libelf build is described in its own SConscript file.
 # SConscript-local is the per-config build, which just copies some
 # header files into a place where they can be found.
diff --git a/arch/SConscript b/arch/SConscript
index 2d8e34b7b..51f6cc023 100644
--- a/arch/SConscript
+++ b/arch/SConscript
@@ -31,11 +31,17 @@ import os.path
 # Import build environment variable from SConstruct.
 Import('env')
 
+# Right now there are no source files immediately in this directory
+sources = []
+
+#################################################################
 #
 # ISA "switch header" generation.
 #
 # Auto-generate arch headers that include the right ISA-specific
 # header based on the setting of THE_ISA preprocessor variable.
+#
+#################################################################
 
 # List of headers to generate
 isa_switch_hdrs = Split('''
@@ -72,3 +78,69 @@ switch_hdr_action = Action(gen_switch_hdr, gen_switch_hdr_string,
 # Instantiate actions for each header
 for hdr in isa_switch_hdrs:
     env.Command(hdr, [], switch_hdr_action)
+
+#################################################################
+#
+# Include architecture-specific files.
+#
+#################################################################
+
+#
+# Build a SCons scanner for ISA files
+#
+import SCons.Scanner
+
+def ISAScan():
+   return SCons.Scanner.Classic("ISAScan",
+                                "$ISASUFFIXES",
+                                "SRCDIR",
+                                '^[ \t]*##[ \t]*include[ \t]*"([^>"]+)"')
+
+def ISAPath(env, dir, target=None, source=None, a=None):
+   return (Dir(env['SRCDIR']), Dir('.'))   
+
+iscan = Scanner(function = ISAScan().scan, skeys = [".isa", ".ISA"],
+                path_function = ISAPath)
+env.Append(SCANNERS = iscan)
+
+#
+# Now create a Builder object that uses isa_parser.py to generate C++
+# output from the ISA description (*.isa) files.
+#
+
+# several files are generated from the ISA description
+isa_desc_gen_files = Split('''
+	decoder.cc
+        alpha_o3_exec.cc
+	fast_cpu_exec.cc
+        simple_cpu_exec.cc
+        full_cpu_exec.cc
+	decoder.hh
+        ''')
+
+# Convert to File node to fix path
+isa_parser = File('isa_parser.py')
+
+# The emitter patches up the sources & targets to include the
+# autogenerated files as targets and isa parser itself as a source.
+def isa_desc_emitter(target, source, env):
+    return (isa_desc_gen_files, [isa_parser] + source)
+
+# Pieces are in place, so create the builder.
+isa_desc_builder = Builder(action='${SOURCES[0]} ${SOURCES[1]} $TARGET.dir',
+                           source_scanner = iscan,
+                           emitter = isa_desc_emitter)
+
+env.Append(BUILDERS = { 'ISADesc' : isa_desc_builder })
+
+#
+# Now include other ISA-specific sources from the ISA subdirectories.
+#
+
+isa = env['TARGET_ISA'] # someday this may be a list of ISAs
+
+# Let the target architecture define what additional sources it needs
+sources += SConscript(os.path.join(isa, 'SConscript'),
+                      exports = 'env', duplicate = False)
+
+Return('sources')
diff --git a/arch/alpha/SConscript b/arch/alpha/SConscript
index a5ae77dac..050dfb9cf 100644
--- a/arch/alpha/SConscript
+++ b/arch/alpha/SConscript
@@ -43,40 +43,45 @@ Import('env')
 ###################################################
 
 # Base sources used by all configurations.
-arch_base_sources = Split('''
-	arch/alpha/decoder.cc
-        arch/alpha/alpha_o3_exec.cc
-	arch/alpha/fast_cpu_exec.cc
-	arch/alpha/simple_cpu_exec.cc
-	arch/alpha/full_cpu_exec.cc
-	arch/alpha/faults.cc
-	arch/alpha/isa_traits.cc
+base_sources = Split('''
+	faults.cc
+	isa_traits.cc
 	''')
 
 # Full-system sources
-arch_full_system_sources = Split('''
-	arch/alpha/alpha_memory.cc
-	arch/alpha/arguments.cc
-	arch/alpha/ev5.cc
-	arch/alpha/osfpal.cc
-	arch/alpha/stacktrace.cc
-	arch/alpha/vtophys.cc
+full_system_sources = Split('''
+	alpha_memory.cc
+	arguments.cc
+	ev5.cc
+	osfpal.cc
+	stacktrace.cc
+	vtophys.cc
 	''')
 
 
 # Syscall emulation (non-full-system) sources
-arch_syscall_emulation_sources = Split('''
-	arch/alpha/alpha_common_syscall_emul.cc
-	arch/alpha/alpha_linux_process.cc
-	arch/alpha/alpha_tru64_process.cc
+syscall_emulation_sources = Split('''
+	alpha_common_syscall_emul.cc
+	alpha_linux_process.cc
+	alpha_tru64_process.cc
 	''')
 
 # Set up complete list of sources based on configuration.
-sources = arch_base_sources
+sources = base_sources
 
 if env['FULL_SYSTEM']:
-    sources += arch_full_system_sources
+    sources += full_system_sources
 else:
-    sources += arch_syscall_emulation_sources
+    sources += syscall_emulation_sources
+
+# Convert file names to SCons File objects.  This takes care of the
+# path relative to the top of the directory tree.
+sources = [File(s) for s in sources]
+
+# Add in files generated by the ISA description.
+isa_desc_files = env.ISADesc('isa/main.isa')
+# Only non-header files need to be compiled.
+isa_desc_sources = [f for f in isa_desc_files if not f.path.endswith('.hh')]
+sources += isa_desc_sources
 
 Return('sources')
diff --git a/arch/isa_parser.py b/arch/isa_parser.py
index b92d267c9..a2bf31a0c 100755
--- a/arch/isa_parser.py
+++ b/arch/isa_parser.py
@@ -1751,7 +1751,7 @@ def preprocess_isa_desc(isa_desc):
 #
 # Read in and parse the ISA description.
 #
-def parse_isa_desc(isa_desc_file, output_dir, include_path):
+def parse_isa_desc(isa_desc_file, output_dir):
     # set a global var for the input filename... used in error messages
     global input_filename
     input_filename = isa_desc_file
@@ -1781,7 +1781,7 @@ def parse_isa_desc(isa_desc_file, output_dir, include_path):
     update_if_needed(output_dir + '/decoder.hh', file_template % vars())
 
     # generate decoder.cc
-    includes = '#include "%s/decoder.hh"' % include_path
+    includes = '#include "decoder.hh"'
     global_output = global_code.decoder_output
     namespace_output = namespace_code.decoder_output
     # namespace_output += namespace_code.decode_block
@@ -1790,7 +1790,7 @@ def parse_isa_desc(isa_desc_file, output_dir, include_path):
 
     # generate per-cpu exec files
     for cpu in CpuModel.list:
-        includes = '#include "%s/decoder.hh"\n' % include_path
+        includes = '#include "decoder.hh"\n'
         includes += cpu.includes
         global_output = global_code.exec_output[cpu.name]
         namespace_output = namespace_code.exec_output[cpu.name]
@@ -1800,4 +1800,4 @@ def parse_isa_desc(isa_desc_file, output_dir, include_path):
 
 # Called as script: get args from command line.
 if __name__ == '__main__':
-    parse_isa_desc(sys.argv[1], sys.argv[2], sys.argv[3])
+    parse_isa_desc(sys.argv[1], sys.argv[2])
diff --git a/arch/mips/SConscript b/arch/mips/SConscript
index a6af91669..b8efa7ef9 100644
--- a/arch/mips/SConscript
+++ b/arch/mips/SConscript
@@ -40,42 +40,44 @@ Import('env')
 ###################################################
 
 # Base sources used by all configurations.
-arch_base_sources = Split('''
-	arch/mips/decoder.cc
-        arch/mips/mips_o3_exec.cc
-	arch/mips/fast_cpu_exec.cc
-	arch/mips/simple_cpu_exec.cc
-	arch/mips/full_cpu_exec.cc
-	arch/mips/faults.cc
-	arch/mips/isa_traits.cc
+base_sources = Split('''
+	faults.cc
+	isa_traits.cc
 	''')
 
 # Full-system sources
-arch_full_system_sources = Split('''
-	arch/mips/memory.cc
-	arch/mips/arguments.cc
-	arch/mips/mips34k.cc
-	arch/mips/osfpal.cc
-	arch/mips/stacktrace.cc
-	arch/mips/vtophys.cc
+full_system_sources = Split('''
+	memory.cc
+	arguments.cc
+	mips34k.cc
+	osfpal.cc
+	stacktrace.cc
+	vtophys.cc
 	''')
 
 # Syscall emulation (non-full-system) sources
-arch_syscall_emulation_sources = Split('''
-	arch/mips/common_syscall_emul.cc
-	arch/mips/linux_process.cc
-	arch/mips/tru64_process.cc
+syscall_emulation_sources = Split('''
+	common_syscall_emul.cc
+	linux_process.cc
+	tru64_process.cc
 	''')
 
 # Set up complete list of sources based on configuration.
-sources = arch_base_sources
+sources = base_sources
 
 if env['FULL_SYSTEM']:
-    sources += arch_full_system_sources
+    sources += full_system_sources
 else:
-    sources += arch_syscall_emulation_sources
+    sources += syscall_emulation_sources
 
-for opt in env.ExportOptions:
-    env.ConfigFile(opt)
+# Convert file names to SCons File objects.  This takes care of the
+# path relative to the top of the directory tree.
+sources = [File(s) for s in sources]
+
+# Add in files generated by the ISA description.
+isa_desc_files = env.ISADesc('isa/main.isa')
+# Only non-header files need to be compiled.
+isa_desc_sources = [f for f in isa_desc_files if not f.path.endswith('.hh')]
+sources += isa_desc_sources
 
 Return('sources')
diff --git a/arch/sparc/SConscript b/arch/sparc/SConscript
index d8a3749a1..fea31fd5d 100644
--- a/arch/sparc/SConscript
+++ b/arch/sparc/SConscript
@@ -40,43 +40,43 @@ Import('env')
 ###################################################
 
 # Base sources used by all configurations.
-arch_base_sources = Split('''
-	arch/sparc/decoder.cc
-        arch/sparc/alpha_o3_exec.cc
-	arch/sparc/fast_cpu_exec.cc
-	arch/sparc/simple_cpu_exec.cc
-	arch/sparc/full_cpu_exec.cc
-	arch/sparc/faults.cc
-	arch/sparc/isa_traits.cc
+base_sources = Split('''
+	faults.cc
+	isa_traits.cc
 	''')
 
 # Full-system sources
-arch_full_system_sources = Split('''
-	arch/sparc/alpha_memory.cc
-	arch/sparc/arguments.cc
-	arch/sparc/ev5.cc
-	arch/sparc/osfpal.cc
-	arch/sparc/stacktrace.cc
-	arch/sparc/vtophys.cc
+full_system_sources = Split('''
+	alpha_memory.cc
+	arguments.cc
+	ev5.cc
+	osfpal.cc
+	stacktrace.cc
+	vtophys.cc
 	''')
 
 # Syscall emulation (non-full-system) sources
-arch_syscall_emulation_sources = Split('''
-	arch/sparc/alpha_common_syscall_emul.cc
-	arch/sparc/alpha_linux_process.cc
-	arch/sparc/alpha_tru64_process.cc
+syscall_emulation_sources = Split('''
+	alpha_common_syscall_emul.cc
+	alpha_linux_process.cc
+	alpha_tru64_process.cc
 	''')
 
-sources = arch_base_sources
+sources = base_sources
 
 if env['FULL_SYSTEM']:
-    sources += arch_full_system_sources
-    if env['ALPHA_TLASER']:
-        sources += arch_turbolaser_sources
+    sources += full_system_sources
 else:
-    sources += arch_syscall_emulation_sources
+    sources += syscall_emulation_sources
 
-for opt in env.ExportOptions:
-    env.ConfigFile(opt)
+# Convert file names to SCons File objects.  This takes care of the
+# path relative to the top of the directory tree.
+sources = [File(s) for s in sources]
+
+# Add in files generated by the ISA description.
+isa_desc_files = env.ISADesc('isa/main.isa')
+# Only non-header files need to be compiled.
+isa_desc_sources = [f for f in isa_desc_files if not f.path.endswith('.hh')]
+sources += isa_desc_sources
 
 Return('sources')