From: Luke Kenneth Casson Leighton <lkcl@lkcl.net>
Date: Tue, 26 Oct 2021 12:47:10 +0000 (+0100)
Subject: add fft butterfly diagram
X-Git-Tag: opf_rfc_ls005_v1~3523
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=0b272b4d43e1c24cd50c783064a85154a0c2defd;p=libreriscv.git

add fft butterfly diagram
---

diff --git a/conferences/openpower2021/fft_butterfly.png b/conferences/openpower2021/fft_butterfly.png
new file mode 100644
index 000000000..1bb3c2acd
Binary files /dev/null and b/conferences/openpower2021/fft_butterfly.png differ
diff --git a/conferences/openpower2021/openpower_2021.tex b/conferences/openpower2021/openpower_2021.tex
index 71d844309..ff1e7500a 100644
--- a/conferences/openpower2021/openpower_2021.tex
+++ b/conferences/openpower2021/openpower_2021.tex
@@ -242,14 +242,15 @@ sv.fmadds: uses fp0 as accumulator
   \end{itemize}
 }
 
-\frame{\frametitle{nmigen PowerISA Decoder}
+
+\frame{\frametitle{Discrete Cosine Transform (DCT): Basics}
 
  \begin{itemize}
    \item Standard DCT Schedule (messy, impossible for SIMD)
    \item Output is in bit-reversed order\\
          0b000 = 0b000 (in: 0   out: 0)\\
-         0b001 = 0b100 (in: 1   out: 4)\\
-         0b110 = 0b011 (in: 7   out: 3)
+         0b001 = 0b100 (in: 1   out: 4) ...\\
+         0b110 = 0b011 (in: 6   out: 3)\\
          0b111 = 0b111 (in: 7   out: 7)
   \end{itemize}
 
@@ -259,6 +260,19 @@ sv.fmadds: uses fp0 as accumulator
 
 }
 
+\frame{\frametitle{Fast Fourier Transform (FFT/DFT): Butterfly Basics}
+
+ \begin{itemize}
+   \item Standard Butterfly Schedule (again: messy, but less so)
+   \item Output, again, is in bit-reversed order
+  \end{itemize}
+
+\begin{center}
+\includegraphics[width=0.70\textwidth]{fft_butterfly.png}
+\end{center}
+
+}
+
 
 \frame{\frametitle{TODO rewrite Summary}