conferences/fosdem2024/fosdem2024_ddffirst/fosdem2024_ddffirst.tex

   1 \documentclass[slidestop]{beamer}
   2 \usepackage{beamerthemesplit}
   3 \usepackage{graphics}
   4 \usepackage{pstricks}
   5 \usepackage{pgffor}
   6 \usepackage{listings}
   7
   8 \graphicspath{{./}}
   9
  10 \title{Data-Dependent-Fail-First}
  11 \author{Luke Kenneth Casson Leighton and Shriya Sharma}
  12
  13
  14 \begin{document}
  15
  16 \frame{
  17    \begin{center}
  18     \huge{The Libre-SOC Hybrid 3D CPU}\\
  19     \vspace{32pt}
  20     \Large{Data-Dependent-Fail-First}\\
  21
  22     \vspace{24pt}
  23     \Large{FOSDEM2024}\\
  24     \vspace{16pt}
  25     \large{Sponsored by NLnet's PET Programme}\\
  26     \vspace{6pt}
  27     \large{\today}
  28   \end{center}
  29 }
  30
  31
  32 \frame{\frametitle{Why another SoC?}
  33
  34  \begin{itemize}
  35    \item Intel Management Engine, Apple QA issues, Spectre\vspace{6pt}
  36    \item Endless proprietary drivers, "simplest" solution: \\
  37          License proprietary hard macros (with proprietary firmware)\\
  38                  Adversely affects product development cost\\
  39                 due to opaque driver bugs (Samsung S3C6410 / S5P100)
  40                  \vspace{6pt}
  41    \item Alternative: Intel and Valve-Steam collaboration\\
  42          "Most productive business meeting ever!"\\
  43          https://tinyurl.com/valve-steam-intel
  44                 \vspace{6pt}
  45    \item Because for 30 years I Always Wanted To Design A CPU
  46                 \vspace{6pt}
  47    \item Ultimately it is a strategic \textit{business} objective to
  48          develop entirely Libre hardware, firmware and drivers.
  49   \end{itemize}
  50 }
  51
  52
  53
  54 \frame{\frametitle{How can you help?}
  55
  56 \vspace{5pt}
  57
  58  \begin{itemize}
  59    \item Start here! https://libre-soc.org \\
  60              Mailing lists https://lists.libre-soc.org \\
  61              IRC Freenode libre-soc \\
  62              etc. etc. (it's a Libre project, go figure) \\
  63                    \vspace{3pt}
  64    \item Can I get paid? Yes!  NLnet funded\\
  65                  See https://libre-soc.org/nlnet/\#faq \\
  66                  \vspace{3pt}
  67    \item Also profit-sharing in any commercial ventures \\
  68              \vspace{3pt}
  69    \item How many opportunities to develop Libre SoCs exist,\\
  70              and actually get paid for it?
  71                      \vspace{3pt}
  72    \item I'm not a developer, how can I help?\\
  73                 - Plenty of research needed, artwork, website \\
  74                 - Help find customers and OEMs willing to commit (LOI)
  75   \end{itemize}
  76 }
  77
  78
  79
  80 \frame{\frametitle{What goes into a typical SoC?}
  81 \vspace{9pt}
  82  \begin{itemize}
  83    \item 15 to 20mm BGA package: 2.5 to 5 watt power consumption\\
  84                 heat sink normally not required (simplifies overall design)
  85                 \vspace{3pt}
  86    \item Fully-integrated peripherals (not Northbridge/Southbridge)\\
  87          USB, HDMI, RGB/TTL, SD/MMC, I2C, UART, SPI, GPIO etc. etc.
  88          \vspace{3pt}
  89    \item Built-in GPU (shared memory bus, 3rd party licensed) \vspace{3pt}
  90    \item Built-in VPU (likewise, proprietary)\vspace{3pt}
  91    \item Target price between \$2.50 and \$30 depending on market\\
  92          Radically different from IBM POWER9 Core (200 Watt)
  93          \vspace{3pt}
  94    \item We're doing the same, just with a hybrid architecture.\\
  95                  CPU == GPU == VPU
  96   \end{itemize}
  97 }
  98
  99
 100
 101 \frame{\frametitle{Simple SBC-style SoC}
 102
 103 \begin{center}
 104 \includegraphics[width=0.6\textwidth]{pospopcount.png}
 105 \end{center}
 106
 107 }
 108
 109
 110
 111
 112 \begin{frame}[fragile]
 113 \frametitle{Simple-V CMPI in a nutshell}
 114
 115 \begin{semiverbatim}
 116 function op\_cmpi(BA, RA, SI) # cmpi not vector-cmpi!
 117   (assuming you know power-isa)
 118   int i, id=0, ira=0;
 119   for (i = 0; i < VL; i++)
 120     CR[BA+id] <= compare(ireg[RA+ira], SI);
 121     if (reg\_is\_vectorised[BA] ) \{ id += 1; \}
 122     if (reg\_is\_vectorised[RA])  \{ ira += 1; \}
 123 \end{semiverbatim}
 124
 125   \begin{itemize}
 126    \item Above is oversimplified: predication etc. left out
 127    \item Scalar-scalar and scalar-vector and vector-vector now all in one
 128    \item OoO may choose to push CMPIs into instr. queue (v. busy!)
 129   \end{itemize}
 130 \end{frame}
 131
 132
 133
 134 \begin{frame}[fragile]
 135 \frametitle{Data-Dependent-Fail-First in a nutshell}
 136
 137 \begin{semiverbatim}
 138         while srcstep < VL - 1
 139                 RT[SS], Rc = DO (MAXS, RA[SS], RB)
 140                 if test (Rc) == FAIL: VL = srcstep + 1, break
 141
 142 \end{semiverbatim}
 143
 144 \begin{itemize}
 145         \item Above is oversimplified: predication etc. left out
 146         \item Scalar-scalar and scalar-vector and vector-vector now all in one
 147         \item OoO may choose to push CMPIs into instr. queue (v. busy!)
 148 \end{itemize}
 149 \end{frame}
 150
 151 \frame{\frametitle{Load/Store Fault-First}
 152
 153         \begin{itemize}
 154                 \item Problem: vector load and store can cause a page fault
 155                 \item Solution: a protocol that allows optional load/store
 156                 \item instruction \textit{requests} a number of elements
 157                 \item instruction \textit{informs} the number actually loaded
 158                 \item first load/store is not optional
 159         \end{itemize}
 160 }
 161
 162
 163
 164 \frame{\frametitle{Additional Simple-V features}
 165
 166  \begin{itemize}
 167    \item "fail-on-first" (POWER9 VSX strncpy segfaults on boundary!)
 168    \item "Twin Predication" (covers VSPLAT, VGATHER, VSCATTER, VINDEX etc.)
 169    \item SVP64: extensive "tag" (Vector context) augmentation
 170    \item "Context propagation": a VLIW-like context.  Allows contexts
 171          to be repeatedly applied.
 172           Effectively a "hardware compression algorithm" for ISAs.
 173    \item Ultimate goal: cut down I-Cache usage, cuts down on power
 174    \item Typical GPU has its own I-Cache and small shaders.\\
 175         \textit{We are a Hybrid CPU/GPU: I-Cache is not separate!}
 176    \item Needs to go through OpenPOWER Foundation `approval'
 177   \end{itemize}
 178 }
 179
 180 \frame{\frametitle{maxloc}
 181   \begin{itemize}
 182                 \item "TODO
 183   \end{itemize}
 184 }
 185
 186 \frame{\frametitle{Pospopcount}
 187
 188   \begin{itemize}
 189         \item   Positional popcount adds up the totals of each bit set to 1 in each bit-position, of an array of input values.
 190         \item   Notoriously difficult to do in SIMD assembler: typically 550 lines
 191    \end{itemize}
 192
 193         \lstinputlisting[language={}]{pospopcount.c}
 194
 195 }
 196 \frame{\frametitle{Pospopcount.s}
 197
 198
 199 \lstinputlisting[language={}]{pospopcount.s}
 200
 201 }
 202
 203
 204 \frame{\frametitle{strncpy}
 205
 206   \begin{itemize}
 207         \item "TODO
 208  \end{itemize}
 209 }
 210
 211 \frame{\frametitle{strncpy assembler}
 212
 213 \lstinputlisting[language={}]{strncpy.s}
 214
 215 }
 216
 217 \frame{\frametitle{linked-list walking}
 218   \begin{itemize}
 219         \item "TODO
 220  \end{itemize}
 221 }
 222 \frame{\frametitle{Summary}
 223
 224  \begin{itemize}
 225    \item Goal is to create a mass-volume low-power embedded SoC suitable
 226          for use in netbooks, chromebooks, tablets, smartphones, IoT SBCs.
 227    \item No way we could implement a project of this magnitude without
 228          nmigen (being able to use python OO to  HDL)
 229    \item Collaboration with OpenPOWER Foundation and Members absolutely
 230          essential. No short-cuts.  Standards to be developed and ratified
 231          so that everyone benefits.
 232    \item Riding the wave of huge stability of OpenPOWER ecosystem
 233    \item Greatly simplified open 3D and Video drivers reduces product
 234          development costs for customers
 235    \item It also happens to be fascinating, deeply rewarding technically
 236          challenging, and funded by NLnet
 237
 238   \end{itemize}
 239 }
 240
 241
 242 \frame{
 243   \begin{center}
 244     {\Huge The end\vspace{12pt}\\
 245                    Thank you\vspace{12pt}\\
 246                    Questions?\vspace{12pt}
 247         }
 248   \end{center}
 249
 250   \begin{itemize}
 251         \item Discussion: http://lists.libre-soc.org
 252         \item Freenode IRC \#libre-soc
 253         \item http://libre-soc.org/
 254         \item http://nlnet.nl/PET
 255         \item https://libre-soc.org/nlnet/\#faq
 256   \end{itemize}
 257 }
 258
 259
 260 \end{document}