diff --git a/BasiliskII/ChangeLog b/BasiliskII/ChangeLog
index 8bb8f9fc..8f619123 100644
--- a/BasiliskII/ChangeLog
+++ b/BasiliskII/ChangeLog
@@ -1,6 +1,9 @@
 V0.9 - <insert date here>
 	- Unix: some performance improvements to VOSF screen update code
 	  [Brian J. Johnson]
+	- Unix: -Ofast option is supplied to MIPSPro compiler [Brian J. Johnson]
+	- Unix: workaround for IRIX pthreads bug in Delay_usec()
+	  [Brian J. Johnson]
 
 V0.9 (snapshot) - 17.Feb.2001
 	- adapted for mon V3.0 which is now the required minimum
diff --git a/BasiliskII/src/Unix/configure.in b/BasiliskII/src/Unix/configure.in
index 67ca7e74..55264bb6 100644
--- a/BasiliskII/src/Unix/configure.in
+++ b/BasiliskII/src/Unix/configure.in
@@ -279,6 +279,16 @@ irix*)
   dnl IRIX headers work fine, but somehow don't define or use "STDC_HEADERS"
   DEFINES="$DEFINES -DCRTSCTS=CNEW_RTSCTS -DB230400=B115200 -DSTDC_HEADERS"
   LIBS="$LIBS -laudio"
+
+  dnl Check if our compiler supports -Ofast (MIPSPro)
+  HAVE_OFAST=no
+  ocflags="$CFLAGS"
+  CFLAGS=`echo $CFLAGS | sed -e 's/ -g / -Ofast /;s/^-g /-Ofast /;s/-g$/ -Ofast/;s/^-g$/-Ofast/'`
+  AC_MSG_CHECKING(if "-Ofast" works)
+  dnl Do a test compile of an empty function
+  AC_TRY_COMPILE(,, [AC_MSG_RESULT(yes); HAVE_OFAST=yes], AC_MSG_RESULT(no))
+  CFLAGS="$ocflags"
+
   ;;
 esac
 
@@ -666,6 +676,14 @@ if [[ "x$HAVE_GCC27" = "xyes" ]]; then
   CXXFLAGS=`echo $CXXFLAGS | sed -e 's/ -g / /;s/^-g / /;s/ -g$/ /;s/^-g$//'`
 fi
 
+dnl Or if we have -Ofast
+if [[ "x$HAVE_OFAST" = "xyes" ]]; then
+  CFLAGS=`echo $CFLAGS | sed -e 's/ -g / -Ofast /;s/^-g /-Ofast /;s/-g$/ -Ofast/;s/^-g$/-Ofast/'`
+  CXXFLAGS=`echo $CXXFLAGS | sed -e 's/ -g / -Ofast /;s/^-g /-Ofast/;s/ -g$/ -Ofast/;s/^-g$/-Ofast/'`
+  CXXFLAGS="-LANG:std $CXXFLAGS"
+  LDFLAGS="$LDFLAGS -Ofast"
+fi
+
 dnl Generate Makefile.
 AC_SUBST(DEFINES)
 AC_SUBST(SYSSRCS)
diff --git a/BasiliskII/src/Unix/main_unix.cpp b/BasiliskII/src/Unix/main_unix.cpp
index 7e765996..701bf7e9 100644
--- a/BasiliskII/src/Unix/main_unix.cpp
+++ b/BasiliskII/src/Unix/main_unix.cpp
@@ -869,16 +869,26 @@ uint64 GetTicks_usec(void)
 // Linux select() changes its timeout parameter upon return to contain
 // the remaining time. Most other unixen leave it unchanged or undefined.
 #define SELECT_SETS_REMAINING
-#elif defined(__FreeBSD__) || defined(__sun__) || defined(sgi)
+#elif defined(__FreeBSD__) || defined(__sun__)
 #define USE_NANOSLEEP
+#elif defined(HAVE_PTHREADS) && defined(sgi)
+// SGI pthreads has a bug when using pthreads+signals+nanosleep,
+// so instead of using nanosleep, wait on a CV which is never signalled.
+#define USE_COND_TIMEDWAIT
 #endif
 
 void Delay_usec(uint32 usec)
 {
 	int was_error;
 
-#ifdef USE_NANOSLEEP
+#if defined(USE_NANOSLEEP)
 	struct timespec elapsed, tv;
+#elif defined(USE_COND_TIMEDWAIT)
+	// Use a local mutex and cv, so threads remain independent
+	pthread_cond_t delay_cond = PTHREAD_COND_INITIALIZER;
+	pthread_mutex_t delay_mutex = PTHREAD_MUTEX_INITIALIZER;
+	struct timespec elapsed;
+	uint64 future;
 #else
 	struct timeval tv;
 #ifndef SELECT_SETS_REMAINING
@@ -887,22 +897,30 @@ void Delay_usec(uint32 usec)
 #endif
 
 	// Set the timeout interval - Linux only needs to do this once
-#ifdef SELECT_SETS_REMAINING
+#if defined(SELECT_SETS_REMAINING)
     tv.tv_sec = 0;
     tv.tv_usec = usec;
 #elif defined(USE_NANOSLEEP)
     elapsed.tv_sec = 0;
     elapsed.tv_nsec = usec * 1000;
+#elif defined(USE_COND_TIMEDWAIT)
+	future = GetTicks_usec() + usec;
+	elapsed.tv_sec = future / 1000000;
+	elapsed.tv_nsec = (future % 1000000) * 1000;
 #else
     then = GetTicks_usec();
 #endif
 
 	do {
 		errno = 0;
-#ifdef USE_NANOSLEEP
+#if defined(USE_NANOSLEEP)
 		tv.tv_sec = elapsed.tv_sec;
 		tv.tv_nsec = elapsed.tv_nsec;
 		was_error = nanosleep(&tv, &elapsed);
+#elif defined(USE_COND_TIMEDWAIT)
+		was_error = pthread_mutex_lock(&delay_mutex);
+		was_error = pthread_cond_timedwait(&delay_cond, &delay_mutex, &elapsed);
+		was_error = pthread_mutex_unlock(&delay_mutex);
 #else
 #ifndef SELECT_SETS_REMAINING
 		// Calculate the time interval left (in case of interrupt)