diff options
Diffstat (limited to 'doc/supplements/c4x/cpumodel.t')
| -rw-r--r-- | doc/supplements/c4x/cpumodel.t | 82 |
1 files changed, 0 insertions, 82 deletions
diff --git a/doc/supplements/c4x/cpumodel.t b/doc/supplements/c4x/cpumodel.t deleted file mode 100644 index 079c6e15c7..0000000000 --- a/doc/supplements/c4x/cpumodel.t +++ /dev/null @@ -1,82 +0,0 @@ -@c -@c COPYRIGHT (c) 1988-1999. -@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 PowerPC 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 the various implementations of the C3x/C4x architecture -that are of importance to rtems. -the set of cpu model feature macros are defined in the file -cpukit/score/cpu/c4x/rtems/score/c4x.h and are based upon -the particular cpu model defined in the bsp's custom configuration -file as well as the compilation command line. - -@section CPU Model Name - -The macro @code{CPU_MODEL_NAME} is a string which designates -the name of this cpu model. for example, for the c32 -processor, this macro is set to the string "c32". - -@section Floating Point Unit - -The Texas Instruments C3x/C4x family makes little distinction -between the various cpu registers. Although floating point -operations may only be performed on a subset of the cpu registers, -these same registers may be used for normal integer operations. -as a result of this, this port of rtems makes no distinction -between integer and floating point contexts. The routine -@code{_CPU_Context_switch} saves all of the registers that -comprise a task's context. the routines that initialize, -save, and restore floating point contexts are not present -in this port. - -Moreover, there is no floating point context pointer and -the code in @code{_Thread_Dispatch} that manages the -floating point context switching process is disabled -on this port. - -This not only simplifies the port, it also speeds up context -switches by reducing the code involved and reduces the code -space footprint of the executive on the Texas Instruments -C3x/C4x. - |