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| author | Oyvind Harboe <oyvind.harboe@zylin.com> | 2009-01-27 08:33:56 +0100 |
|---|---|---|
| committer | Oyvind Harboe <oyvind.harboe@zylin.com> | 2009-01-27 08:33:56 +0100 |
| commit | 5c6feff72d5324c88e0e8d8980a7d7cfab7e1509 (patch) | |
| tree | 8acd0e1c27891fe61db2221af182a0756f892ca7 | |
| parent | 047351652678c02fc3aa3a6202b0d0f1d996ed48 (diff) | |
| download | zpu-5c6feff72d5324c88e0e8d8980a7d7cfab7e1509.zip zpu-5c6feff72d5324c88e0e8d8980a7d7cfab7e1509.tar.gz | |
First cut of ZPU floating point support design
| -rw-r--r-- | zpu/docs/zpu_arch.html | 51 |
1 files changed, 51 insertions, 0 deletions
diff --git a/zpu/docs/zpu_arch.html b/zpu/docs/zpu_arch.html index 5a55378..6266a03 100644 --- a/zpu/docs/zpu_arch.html +++ b/zpu/docs/zpu_arch.html @@ -66,6 +66,7 @@ Several of the links will only work if you have checked out the zpu/zpu tree fro <li> <a href="#todolist">TODO list</a>
<li> <a href="#repository">Repository Re-org</a>
<li> <a href="#nextgen">Next generation ZPU</a>
+ <li> <a href="#float">Floating point support</a>
</ul>
</ul>
@@ -2319,5 +2320,55 @@ function calls to libgcc and thus make it easier to determine that microcode is not needed.
</ol>
+<a name="float"/>
+<h1>Floating point support</h1>
+The ZPU does not currently have floating point support. Feedback
+from users indicates that single precision floating point support for
+addition, multiplication and float-to-integer convesion would
+be useful for small ZPU programs that sit in a tight control
+loop. Essentially the ZPU is then measuring something, doing a
+few calculations and then modifying the control signal.
+<p>
+Such control loops can be written in fixed point math, but that
+adds to the engineering effort and reduces clarity of the software
+implementation and the performance will probably be worse than
+for a hardware floating point version.
+<h2>Pipelined floating point module</h2>
+Design needs to be nailed down.
+<b>Goals:</b>
+<ul>
+<li> 32 bit single precision floating point
+<li> FADD => add two floats
+<li> FMULT => multiply two floats
+<li> FINT => convert float to int
+</ul>
+The problem is divided into two:
+
+<ol>
+<li>One top level VHDL module for each of the operations above.
+<li>Integration into ZPU's are a separate problem that will not be
+addressed in this project.
+<li>add a memory mapped coprocessor interface to the above. This
+yields an example of a coprocessor which can be used for any
+custom calculations and allows interest to be gauged.
+</ol>
+
+Throughput:
+
+<ol>
+<li>pipelined design where throughput is one operation per cycle
+with a fixed number of cycles delay.
+<li>there is no flow control or enable signal.
+</ol>
+
+
+
+GCC support is not hard, but modifying GCC should considered after
+interest in this feature beyond a coprocessor has been gauged.
+
+<h2>VHDL module interface</h2>
+
+Patches anyone???
+
</body>
<html>
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