PS/2 mouse now correctly returns 0xFE on bad command;

The FDC now correctly turns off the drive icon's activity light on finishing the READ SECTOR ID command;
Pentium, i686, and some 486 machines now have realistic (per their documentations) minimum and maximum RAM sizes and RAM granularities.

src/mouse_ps2.c

@@ -55,7 +55,10 @@ void mouse_ps2_write(uint8_t val, void *p)
                         mouse->sample_rate = val;
                         keyboard_at_adddata_mouse(0xfa);
                         break;
-                        
+
+			default:
+			keyboard_at_adddata_mouse(0xfc);
+
 //                        default:
 //                        fatal("mouse_ps2 : Bad data write %02X for command %02X\n", val, mouse->command);
                 }
@@ -128,6 +131,9 @@ void mouse_ps2_write(uint8_t val, void *p)
                         keyboard_at_adddata_mouse(0x00);
                         break;
 
+			default:
+			keyboard_at_adddata_mouse(0xfe);
+
 //                        default:
 //                        fatal("mouse_ps2 : Bad command %02X\n", val, mouse->command);
                 }