Conference on Adaptive Hardware and Systems (AHS'14) - The DSP for FlexTiles

www.flextiles.eu
FlexTiles
Workshop at AHS’2014 conference: FlexTiles FP7 project
Low-Power DSP Accelerator
Embedded in a Heterogeneous
Many-Core Architecture
Marc MORGAN
CSEM – Swiss Center for Electronics and
Microtechnology

1 /
TheinformationcontainedinthisdocumentandanyattachmentsarethepropertyofFlexTilesconsortium.Youareherebynotifiedthatanyreview,dissemination,distribution,
copyingorotherwiseuseofthisdocumentmustbedoneinaccordancewiththeCAoftheproject(TRT/DJ/624412785.2011).Templateversion1.0
CSEM overview on a single slide
• private company, founded in the 1980’s, not for profit
• approx. 400 employees on 5 sites in Switzerland (HQ in Neuchatel)
and a site Brazil
• 5 research programs:
1. ultra-low power integrated systems (SoC, Vision, Wireless)
2. systems engineering (med tech, instrumentation, automation)
3. MEMS
4. surface engineering (nano, bio, printable electronics)
5. photovoltaic
• approx. 70 MCHF annual budget
• over 20 start-ups and spin-offs since 1995

2 /
Many-core architecture: GPPs + accelerators
• An array of general purpose processors (GPP)
• Connected via a Network-on-Chip (NoC)
• Complemented with accelerators to optimize speed and power:
 DSP processors or specialized logic implemented in embedded-
FPGA
• Plus memory nodes and I/O

3 /
Many-core architecture: GPPs + accelerators (cont’d)
Several IPs are available for the building blocks
 both in the consortium and on the market
 architectural choices attempt to retain genericity of the platform
CSEM provides an ultra-low power DSP processor for the DSP
accelerator
It plugs into a generic accelerator interface (AI)

4 /
Accelerator interface (AI)
Interfaces the NoC’s NI to the accelerator by providing services:
 programming, control/status, data in, data out, debug
 DMA access, word FIFOs, notification

5 /
DSP accelerator architecture
Choices for the DSP accelerator avoid DSP specific features
 the DSP will not run an OS or kernel
 the DSP will not use (or at least not require) interruptions
 Note: CSEM’s icyflex4 ULP DSP could support both of the above
Implement a FIFO manager to handle input and output tokens from/to
the accelerator interface (AI)
Implement debug and tracing facilities
 Debug: JTAG 1149.1 TAP
 Tracing: programmable tracing unit

6 /
DSP accelerator architecture (cont’d)

7 /
Management of the DSP accelerator
Each accelerator is managed by software running on GPPs
 virtualization manager: attribution of the accelerator
 resource manager: control of the accelerator
These managers are in charge of:
 transfer of the application (ELF) to the accelerator
 signaling the accelerator when to start and when to stop
 recovering statistics on usage of the accelerator to optimize the
execution of the application on the many-core platform
The tracing unit can be managed from the processor or from the JTAG
interface

8 /
Ultra low-power (ULP) processors at CSEM
CSEM was founded in the 1980s to promote innovation
1980s, initially for the Swiss watch industry
 ULP 4-bit processors: PUNCH, µPUS, Combo, ...
1990s, development of a general purpose ULP 8-bit processor:
 CoolRISC: licensed to Swatch group, TI, Semtech, ...
2000s, powerful new ULP processors with DSP features
 2006: icyflex1, a flexible processor for DSP/control apps
 2009: icyflex2, a smaller processor for control applications
 2009: icyflex4, a scalable processor for DSP/control apps
icyflex is a registered trademark of CSEM

9 /
icyflex family of ultra-low power processors
icyflex2Control
Computing
Power
DSP
icyflex1
icyflex4
1 MUL 2 MAC 4 MAC … 36 MAC
Application
6 µW/MHz
25 µW/MHz 10-150 µW/MHz
12 MAC
power indicated for TSMC 65 nm CMOS

10 /
icyflex software development kit
GNU C compiler (gcc) v 4.6.3
 icyflex instruction parallelism supported by latest releases of gcc
 libc and libm from RedHat’s NewLib
 software implementation of IEEE floating-point standard
GNU assembler / linker (binutils), v 2.20
 BFD / ELF32 object file format
 Binary, SREC, IHEX memory image file formats
GNU debugger (gdb), v 6.7.1
 Mode 1: instruction set simulator of the icyflex core
 Mode 2: On-Chip Debug (OCD) through a JTAG interface
icyflex instruction set simulator (ISS), written in C++
 Phase-accurate, pipelined
 Wrappers to SystemC, VHDL (Modelsim), Matlab/Simulink
Eclipse integrated development environment, v Helios
 CDT C/C++ IDE plug-in
 icyflex plug-in
.c
.o
.exe
.log
gcc
ld
gdbgdb

11 /
icyflex2 vs icyflex4
Feature icyflex2 icyflex4 VPS=2
Optimized for Control DSP
P, X, Y memory buses,
ISA, HW loops,
saturation, …
Instruction word [bits] 32 (1 or 2 sub) 64 (1, 2 or 3 sub)
Memory access [bits] 8, 16 or 32 2x (8, 16, 32, 64, 128)
Data processing [bits] 16 or 32, trunc 2x (16 or 32 or 64), full
Single Instr. Multiple Data (SIMD) No Yes, up to 8 MAC
Instruction set is reconfigurable
on the fly
No Yes
Software Development Kit (SDK) GNU-based tool suite (gcc, gdb) + cycle-
accurate instruction set simulator (ISS)
Hardware Devt Kit (HDK) FPGA-based, customizable
VPS = Vector Processing Slices in the Vector Processing Unit of the DSP

12 /
blank instructions
configured at run-time
icyflex: reconfigurable instructions and addressing modes
Instruction set
ADD
MUL
SHR
MAC
JUMP
configurable
configurable
SHIFT
MUX
ALU
ACC
ACC
SHIFT
MUX
ALU
ACC
ACC
instructiondecoding
cycle N: config MOP
cycle N+1: use MOP

13 /
DSP in FlexTiles emulators
Emulator 1 (software):
 Using Open Virtual Platform (OVP)
 Not cycle accurate
 The icyflex4 DSP is emulated by a GPP running at a higher frequency
Emulator 2 (hardware):
 Using an FPGA board with two Xilinx Virtex6 FPGAs
 Uses a DFF version of the DSP accelerator

14 /
Exploitation of FlexTiles results at CSEM
CSEM specializes in low power solutions
A well-balanced multi-processor design can optimize energy
consumption by reducing voltage and frequency
For multi-core: we offer CSEM solutions
For many-core: CSEM collaborates with 1 or more of our partners
 including e.g. a follow up project to produce FlexTiles chips

15 /
FlexTiles FP7 project
For more information regarding the FlexTiles project, visit:
http://www.flextiles.eu
Please take 5 minutes to fill out the survey
on the project web site under the Contact menu
The FlexTiles project is funded in part by FP7, the seventh
framework programme of the European Commission.

www.flextiles.eu
FlexTiles
Thank you for your attention!
For more information: http://www.csem.ch
Questions? mailto:marc.morgan@csem.ch

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