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authorJoel Sherrill <joel.sherrill@OARcorp.com>1998-10-19 12:49:37 +0000
committerJoel Sherrill <joel.sherrill@OARcorp.com>1998-10-19 12:49:37 +0000
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+@c
+@c COPYRIGHT (c) 1988-1998.
+@c On-Line Applications Research Corporation (OAR).
+@c All rights reserved.
+@c
+@c $Id$
+@c
+
+@chapter CPU Model Dependent Features
+
+@section Introduction
+
+Microprocessors are generally classified into
+families with a variety of CPU models or implementations within
+that family. Within a processor family, there is a high level
+of binary compatibility. This family may be based on either an
+architectural specification or on maintaining compatibility with
+a popular processor. Recent microprocessor families such as the
+SPARC or PA-RISC are based on an architectural specification
+which is independent or any particular CPU model or
+implementation. Older families such as the M68xxx and the iX86
+evolved as the manufacturer strived to produce higher
+performance processor models which maintained binary
+compatibility with older models.
+
+RTEMS takes advantage of the similarity of the
+various models within a CPU family. Although the models do vary
+in significant ways, the high level of compatibility makes it
+possible to share the bulk of the CPU dependent executive code
+across the entire family. Each processor family supported by
+RTEMS has a list of features which vary between CPU models
+within a family. For example, the most common model dependent
+feature regardless of CPU family is the presence or absence of a
+floating point unit or coprocessor. When defining the list of
+features present on a particular CPU model, one simply notes
+that floating point hardware is or is not present and defines a
+single constant appropriately. Conditional compilation is
+utilized to include the appropriate source code for this CPU
+model's feature set. It is important to note that this means
+that RTEMS is thus compiled using the appropriate feature set
+and compilation flags optimal for this CPU model used. The
+alternative would be to generate a binary which would execute on
+all family members using only the features which were always
+present.
+
+This chapter presents the set of features which vary
+across SPARC implementations and are of importance to RTEMS.
+The set of CPU model feature macros are defined in the file
+c/src/exec/score/cpu/XXX/XXX.h based upon the particular CPU
+model defined on the compilation command line.
+
+@section CPU Model Name
+
+The macro CPU_MODEL_NAME is a string which designates
+the name of this CPU model. For example, for the MODEL
+processor, this macro is set to the string "XXX".
+
+@section Floating Point Unit
+
+The macro XXX_HAS_FPU is set to 1 to indicate that
+this CPU model has a hardware floating point unit and 0
+otherwise. It does not matter whether the hardware floating
+point support is incorporated on-chip or is an external
+coprocessor.
+
+@section Another Optional Feature
+
+The macro XXX