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+
+@include ../common/timemac.texi
+@tex
+\global\advance \smallskipamount by -4pt
+@end tex
+
+@ifinfo
+@node MC68020 Timing Data, MC68020 Timing Data Introduction, Memory Requirements RTEMS RAM Workspace Worksheet, Top
+@end ifinfo
+@chapter MC68020 Timing Data
+@ifinfo
+@menu
+* MC68020 Timing Data Introduction::
+* MC68020 Timing Data Hardware Platform::
+* MC68020 Timing Data Interrupt Latency::
+* MC68020 Timing Data Context Switch::
+* MC68020 Timing Data Directive Times::
+* MC68020 Timing Data Task Manager::
+* MC68020 Timing Data Interrupt Manager::
+* MC68020 Timing Data Clock Manager::
+* MC68020 Timing Data Timer Manager::
+* MC68020 Timing Data Semaphore Manager::
+* MC68020 Timing Data Message Manager::
+* MC68020 Timing Data Event Manager::
+* MC68020 Timing Data Signal Manager::
+* MC68020 Timing Data Partition Manager::
+* MC68020 Timing Data Region Manager::
+* MC68020 Timing Data Dual-Ported Memory Manager::
+* MC68020 Timing Data I/O Manager::
+* MC68020 Timing Data Rate Monotonic Manager::
+@end menu
+@end ifinfo
+
+@ifinfo
+@node MC68020 Timing Data Introduction, MC68020 Timing Data Hardware Platform, MC68020 Timing Data, MC68020 Timing Data
+@end ifinfo
+@section Introduction
+
+The timing data for the MC68020 version of RTEMS is
+provided along with the target dependent aspects concerning the
+gathering of the timing data.  The hardware platform used to
+gather the times is described to give the reader a better
+understanding of each directive time provided.  Also, provided
+is a description of the interrupt latency and the context switch
+times as they pertain to the MC68020 version of RTEMS.
+
+@ifinfo
+@node MC68020 Timing Data Hardware Platform, MC68020 Timing Data Interrupt Latency, MC68020 Timing Data Introduction, MC68020 Timing Data
+@end ifinfo
+@section Hardware Platform
+
+All times reported except for the maximum period
+interrupts are disabled by RTEMS were measured using a Motorola
+MVME135 CPU board.  The MVME135 is a 20Mhz board with one wait
+state dynamic memory and a MC68881 numeric coprocessor.  The
+Zilog 8036 countdown timer on this board was used to measure
+elapsed time with a one-half microsecond resolution.  All
+sources of hardware interrupts were disabled, although the
+interrupt level of the MC68020 allows all interrupts.
+
+The maximum period interrupts are disabled was
+measured by summing the number of CPU cycles required by each
+assembly language instruction executed while interrupts were
+disabled.  The worst case times of the MC68020 microprocessor
+were used for each instruction.  Zero wait state memory was
+assumed.  The total CPU cycles executed with interrupts
+disabled, including the instructions to disable and enable
+interrupts, was divided by 20 to simulate a 20Mhz MC68020.  It
+should be noted that the worst case instruction times for the
+MC68020 assume that the internal cache is disabled and that no
+instructions overlap.
+
+@ifinfo
+@node MC68020 Timing Data Interrupt Latency, MC68020 Timing Data Context Switch, MC68020 Timing Data Hardware Platform, MC68020 Timing Data
+@end ifinfo
+@section Interrupt Latency
+
+The maximum period with interrupts disabled within
+RTEMS is less than RTEMS_MAXIMUM_DISABLE_PERIOD 
+microseconds including the instructions
+which disable and re-enable interrupts.  The time required for
+the MC68020 to vector an interrupt and for the RTEMS entry
+overhead before invoking the user's interrupt handler are a
+total of RTEMS_INTR_ENTRY_RETURNS_TO_PREEMPTING_TASK 
+microseconds.  These combine to yield a worst case
+interrupt latency of less than 
+RTEMS_MAXIMUM_DISABLE_PERIOD + RTEMS_INTR_ENTRY_RETURNS_TO_PREEMPTING_TASK 
+microseconds at 20Mhz.  [NOTE:  The maximum period with interrupts
+disabled was last determined for Release 
+RTEMS_RELEASE_FOR_MAXIMUM_DISABLE_PERIOD.]
+
+It should be noted again that the maximum period with
+interrupts disabled within RTEMS is hand-timed and based upon
+worst case (i.e. CPU cache disabled and no instruction overlap)
+times for a 20Mhz MC68020.  The interrupt vector and entry
+overhead time was generated on an MVME135 benchmark platform
+using the Multiprocessing Communications registers to generate
+as the interrupt source.
+
+@ifinfo
+@node MC68020 Timing Data Context Switch, MC68020 Timing Data Directive Times, MC68020 Timing Data Interrupt Latency, MC68020 Timing Data
+@end ifinfo
+@section Context Switch
+
+The RTEMS processor context switch time is RTEMS_NO_FP_CONTEXTS
+microseconds on the MVME135 benchmark platform when no floating
+point context is saved or restored.  Additional execution time
+is required when a TASK_SWITCH user extension is configured.
+The use of the TASK_SWITCH extension is application dependent.
+Thus, its execution time is not considered part of the raw
+context switch time.
+
+Since RTEMS was designed specifically for embedded
+missile applications which are floating point intensive, the
+executive is optimized to avoid unnecessarily saving and
+restoring the state of the numeric coprocessor.  The state of
+the numeric coprocessor is only saved when an FLOATING_POINT
+task is dispatched and that task was not the last task to
+utilize the coprocessor.  In a system with only one
+FLOATING_POINT task, the state of the numeric coprocessor will
+never be saved or restored.  When the first FLOATING_POINT task
+is dispatched, RTEMS does not need to save the current state of
+the numeric coprocessor.
+
+The exact amount of time required to save and restore
+floating point context is dependent on whether an MC68881 or
+MC68882 is being used as well as the state of the numeric
+coprocessor.  These numeric coprocessors define three operating
+states: initialized, idle, and busy.  RTEMS places the
+coprocessor in the initialized state when a task is started or
+restarted.  Once the task has utilized the coprocessor, it is in
+the idle state when floating point instructions are not
+executing and the busy state when floating point instructions
+are executing.  The state of the coprocessor is task specific.
+
+The following table summarizes the context switch
+times for the MVME135 benchmark platform:
+
+@include timetbl.texi
+
+@tex
+\global\advance \smallskipamount by 4pt
+@end tex