diff --git a/Ample/AppDelegate.m b/Ample/AppDelegate.m
index 5c91a5a..2d57b7e 100644
--- a/Ample/AppDelegate.m
+++ b/Ample/AppDelegate.m
@@ -115,11 +115,11 @@
     
     dispatch_time_t when = dispatch_time(DISPATCH_TIME_NOW, (int64_t)(2 * NSEC_PER_SEC));
     [task setTerminationHandler: ^(NSTask *task){
-       
+
+        int st = [task terminationStatus];
+        // delay so the install window is visible, I think
         dispatch_after(when, dispatch_get_main_queue(), ^{
   
-            int st = [task terminationStatus];
-
             if (st) {
                 NSAlert *alert = [NSAlert new];
                 [alert setMessageText: @"An error occurred extracting MAME components"];
@@ -238,4 +238,70 @@
 }
 
 
+-(IBAction)installMameComponents:(id)sender {
+
+      
+      /* install the mame data components. */
+      NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
+      NSBundle *bundle = [NSBundle mainBundle];
+      NSURL *sd = SupportDirectory();
+
+      NSURL *ample_url = [sd URLByAppendingPathComponent: @"Ample.plist"];
+      NSMutableDictionary *d = [NSMutableDictionary dictionaryWithContentsOfURL: ample_url];
+      
+      //NSDate *oldDate = [d objectForKey: kMameComponentsDate];
+      NSDate *newDate = [defaults objectForKey: kMameComponentsDate];
+      if (![newDate isKindOfClass: [NSDate class]])
+          newDate = nil;
+      
+      NSString *path = [bundle pathForResource: @"mame-data" ofType: @"tgz"];
+      if (!path) return; // Ample Lite?
+
+      
+      NSWindow *win = _installWindow;
+      [win makeKeyAndOrderFront: nil];
+      NSTask *task = [NSTask new];
+      NSArray *argv = @[
+          @"xfz",
+          path
+      ];
+      if (@available(macOS 10.13, *)) {
+          [task setExecutableURL: [NSURL fileURLWithPath: @"/usr/bin/tar"]];
+          [task setCurrentDirectoryURL: sd];
+      } else {
+          [task setLaunchPath:  @"/usr/bin/tar"];
+          [task setCurrentDirectoryPath: SupportDirectoryPath()];
+      }
+      [task setArguments: argv];
+
+      
+      //dispatch_time_t when = dispatch_time(DISPATCH_TIME_NOW, (int64_t)(2 * NSEC_PER_SEC));
+      [task setTerminationHandler: ^(NSTask *task){
+
+          int st = [task terminationStatus];
+          dispatch_async(dispatch_get_main_queue(), ^{
+    
+              if (st) {
+                  NSAlert *alert = [NSAlert new];
+                  [alert setMessageText: @"An error occurred extracting MAME components"];
+                  [alert runModal];
+                  [win close];
+                  return;
+              }
+              
+              if (d) {
+                  [d setObject: newDate forKey: kMameComponentsDate];
+                  [d writeToURL: ample_url atomically: YES];
+              } else {
+                  [@{ kMameComponentsDate: newDate } writeToURL: ample_url atomically: YES];
+              }
+              [win close];
+              // need to reload the software list data.
+          });
+          
+      }];
+      [task launch];
+    
+}
+
 @end
diff --git a/Ample/Base.lproj/MainMenu.xib b/Ample/Base.lproj/MainMenu.xib
index 1ef203a..e6f90f9 100644
--- a/Ample/Base.lproj/MainMenu.xib
+++ b/Ample/Base.lproj/MainMenu.xib
@@ -45,6 +45,9 @@
                                 </connections>
                             </menuItem>
                             <menuItem isSeparatorItem="YES" id="VOq-y0-SEH"/>
+                            <menuItem title="Reinstall MAME components" hidden="YES" id="c3P-WT-eUP">
+                                <modifierMask key="keyEquivalentModifierMask"/>
+                            </menuItem>
                             <menuItem title="Preferences…" keyEquivalent="," id="BOF-NM-1cW">
                                 <connections>
                                     <action selector="displayPreferences:" target="Voe-Tx-rLC" id="Hsm-pX-sUc"/>
diff --git a/Ample/SoftwareList.h b/Ample/SoftwareList.h
index 427185a..131e326 100644
--- a/Ample/SoftwareList.h
+++ b/Ample/SoftwareList.h
@@ -39,6 +39,8 @@
 @interface SoftwareSet : NSObject <NSFastEnumeration, AutoCompleteDelegate>
 
 +(instancetype)softwareSetForMachine: (NSString *)machine;
++(void)invalidate;
+
 -(BOOL)nameIsUnique: (NSString *)name;
 
 -(NSString *)nameForSoftware: (Software *)software;
diff --git a/Ample/SoftwareList.m b/Ample/SoftwareList.m
index 63cddaf..0ad4272 100644
--- a/Ample/SoftwareList.m
+++ b/Ample/SoftwareList.m
@@ -512,9 +512,15 @@ NSArray<SoftwareList *> *SoftwareListForMachine(NSString *machine) {
     
 }
 
+
+static NSCache *cache;
++(void)invalidate {
+// called after mame components are updated.  clears the cache.
+    cache = nil;
+}
+
 +(instancetype)softwareSetForMachine:(NSString *)machine {
     
-    static NSCache *cache;
     
     if (!cache)
         cache = [NSCache new];