Patch from Erik Ivanenko <erik.ivanenko@utoronto.ca>:

Please find attached the two files that have been changed  relative to
    980921 .  The changes here are in the handling of the counter-timer used
    as the basis for the rtems executive clock.  For the most part, these
    are housekeeping changes.

    The PSCLK frequency change in start.s... was a part of several
    bug-fixes.  The fix improves executive clock and timer accuracy.

    changes :

    start.s --  All timers are disabled by the initialization routine
            -- PSCLK ( used by clock and timers ) frequency changed to 1MHz

    The clock_initialize routine now assumes that the PSCLK frequency is
    exactly 1 MHz.

    ckinit.c

    Clock_isr            -- removed division by 1000.  Now use 'static'
    variable -- clock_intial_isr_value -- to reset Clock_isrs variable.
    clock_initialize -- moved counter timer initialization here.  Values
    used to configure the timer are totally dependent on
    BSP_configuration.microseconds_per_tick ( and the PSCLK assumption).
    Initializes clock_initial_isr_value used by th Clock_isr to reset
    Clock_isrs.

     clock_on -- no longer configures the timer, just enables it.

    Since altering the number of sections in the BSP, I decided to give it a
    good "once over" .   The clock handling is now cleaner.

c/src/lib/libbsp/i386/i386ex/clock/ckinit.c

@@ -33,6 +33,7 @@
 #include <stdlib.h>
 
 rtems_unsigned32 Clock_isrs;              /* ISRs until next tick */
+static rtems_unsigned32 Clock_initial_isr_value;
 
 volatile rtems_unsigned32 Clock_driver_ticks;
 
@@ -55,7 +56,7 @@ void Clock_isr()
   Clock_driver_ticks += 1;
   if ( Clock_isrs == 1 ) {
     rtems_clock_tick();
-    Clock_isrs = BSP_Configuration.microseconds_per_tick / 1000;
+    Clock_isrs = Clock_initial_isr_value; /* BSP_Configuration.microseconds_per_tick / 1000;*/
   }
   else
     Clock_isrs -= 1;
@@ -63,19 +64,12 @@ void Clock_isr()
 
 void ClockOff(const rtems_irq_connect_data* unused)
 {
-  /* should do something here */;
-  outport_byte	( TMRCFG , 0x80 );
+  outport_byte	( TMRCFG , 0x80 ); /* disable the counter timer */
 }
 
 void ClockOn(const rtems_irq_connect_data* unused)
 {
-  outport_byte	( TMRCFG , 0x80 );
-
-  outport_byte    ( TMRCON , 0x34 ); 
-  outport_byte	( TMR0   , 0xA8 ); 
-  outport_byte    ( TMR0   , 0x04 ); 
-
-  outport_byte    ( TMRCFG , 0x00 ); 
+  outport_byte    ( TMRCFG , 0x00 ); /* enable the counter timer */
 }
 
 int ClockIsOn(const rtems_irq_connect_data* unused)
@@ -95,12 +89,36 @@ rtems_device_driver Clock_initialize(
   void *pargp
 )
 {
+  unsigned timer_counter_init_value;
+  unsigned char clock_lsb, clock_msb;
+  
   Clock_driver_ticks = 0;
-  Clock_isrs = BSP_Configuration.microseconds_per_tick / 1000;
+
+  Clock_isrs = Clock_initial_isr_value = BSP_Configuration.microseconds_per_tick / 1000; /* ticks per clock_isr */
+  
+  /*
+   * configure the counter timer ( should be based on microsecs/tick )
+   * NB. The divisor(Clock_isrs) resolves the  is the same number that appears in confdefs.h
+   * when setting the microseconds_per_tick value.
+   */
+  ClockOff      ( &clockIrqData );
+  
+  timer_counter_init_value  =  BSP_Configuration.microseconds_per_tick / Clock_isrs;
+  clock_lsb = (unsigned char)timer_counter_init_value;
+  clock_msb = timer_counter_init_value >> 8;
+
+  printk("timer_counter_init_value = 0x%x, lsb = 0x%x, msb = 0x%x, Clock_isrs = %d\n",timer_counter_init_value,
+	 clock_lsb, clock_msb, Clock_isrs);
+  
+  outport_byte  ( TMRCON , 0x34 ); 
+  outport_byte	( TMR0   , clock_lsb );       /* load LSB first */
+  outport_byte  ( TMR0   , clock_msb );  /* then MSB       */
+ 
   if (!pc386_install_rtems_irq_handler (&clockIrqData)) {
     printk("Unable to initialize system clock\n");
     rtems_fatal_error_occurred(1);
   }
+
   /*
    * make major/minor avail to others such as shared memory driver
    */

c/src/lib/libbsp/i386/i386ex/start/start.s

@@ -44,6 +44,8 @@ changes:
  * #define NEXT_GAS
  */			
 
+#define NEXT_GAS
+	
         EXTERN (boot_card)         /* exits to bspstart   */ 
 	EXTERN (stack_start)       /* defined in startup/linkcmds */
 	EXTERN (Clock_exit)
@@ -149,14 +151,13 @@ SYM(InitRCU):
 /*
  * Initialize clock and power mgmt unit for:	
  *	Clock Frequency = 50 Mhz
- *	Prescaled clock output = 1.19318 Mhz
- *      ( matches standard PC )
+ *	Prescaled clock output = 1 Mhz
  *      Normal halt instructions
  */
 	
 SYM(InitClk):	 
 	SetExRegByte( PWRCON, 0x0 )
-	SetExRegWord( CLKPRS, 0x13)
+	SetExRegWord( CLKPRS, 0x17)   # 0x13 for 1.19318 MHz.  0x17 for 1MHz.
 
 /**************************************************************
  * Initialize the Pin Configurations
@@ -274,21 +275,19 @@ SYM(InitTimer):
 	                             # and 2 are set to Vcc
 
 	SetExRegByte(TMRCON , 0x34 ) # prepare to write counter 0 LSB,MSB
-	SetExRegByte(TMR0   , 0xA8 ) # LSB = 0B count, followed by MSB 
-	SetExRegByte(TMR0   , 0x04 ) # for INT every 50 msec. MSB = 0xE900
-	                             # for INT every 5  msec. 0x174c
-				     # for INT every 1 msec. 0x04A8
-				     #  was 0xe900
-	
+	SetExRegByte(TMR0   , 0x00 ) # sfa
+	SetExRegByte(TMR0   , 0x00 ) # sfa 
+
+			
 	SetExRegByte(TMRCON , 0x70 ) # mode 0 disables on Gate= Vcc
 	SetExRegByte(TMR1   , 0x00 ) # sfa 
 	SetExRegByte(TMR1   , 0x00 ) # sfa
 	
 	SetExRegByte(TMRCON , 0xB0 ) # mode 0 disables on gate =Vcc
 	SetExRegByte(TMR2   , 0x00 ) #  
-	SetExRegByte(TMR2   , 0x00 ) #
-	SetExRegByte(TMRCFG , 0x80 ) # Enable timers = 0x00 
-  
+	SetExRegByte(TMR2   , 0x00 ) #  
+
+	SetExRegByte(TMRCFG , 0x80 ) # Enable = 0x00
 
 /*
  *	Initialize the DMACFG register for: