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SHAKTI Processor Project

The SHAKTI processor project aims to build variants of processors based on the RISC-V ISA from UC Berkeley (
The project will develop a series of cores, SoC fabrics and a reference SoC for each core family.
While the cores and most of the SoC components (including bus and interconnect fabrics) will be in open source,
some standard components like PCIe controller, DDR controller and PHY IP will be 3rd party IP blocks.

All source is licensed using 3 part BSD license and will be royalty and patent free (as far as IIT-Madras is concerned,
we will not assert any patents). While the primary focus is research, the SoCs are being designed to be competitive
with commercial processors with respect to features, silicon area, power profile
and frequency. This of course assumes that an optimal layout process is used to tape out our design. All FPGA data
will also be made available

While we do plan to tape out a few variants, given the foundry NDA requirements, we will not be able to
publish any layout/backend data. But the ASIC syntesis and P&R data to teh extent possible will be published
to allow others to replicate our ASIC flow.

Contributing to the Project

The quickest way to contribute to the SHAKTI project is to create a pull-request for existing issues or any feature additions.

The SHAKTI team is currently hiring for full-time positions. The work would primarily be involved in the domain of design and verification. Interested candidates please send your resume to


        $ git clone
        $ git submodule update --recursive --remote

Core Variants


  1. 32 bit 3 stage in-order core aimed at 10 - 50 Mhz uC variants
  2. Optional memory protection
  3. Very low power static design
  4. Variants with compressed/reduced ISA support
  5. Bus - AHB Lite

C class

  1. 32 and 64 bit 6 stage in-order core aimed at 10 Mhz - 1 Ghz controller requiremenets
  2. Optional memory protection and MMU
  3. Low power static design varinats
  4. Fault Tolerant variants for ISO26262 applications
  5. IoT variants will have compressed/reduced ISA support
  6. Optional FPU, VPU
  7. Bus - AXI variants

I class

  1. 64-bit, 1-8 core, 8+ stage out of order, aimed at 200 Mhz - 2 Ghz industrial control / general purpose applications
  2. Shared L2 cache, dual threading support, SIMD/VPU
  3. BUS - Shakti NoC + AXI4

M Class

  1. Enhanced variants of the I-class processors aimed at general purpose compute, low end server and mobile applications
  2. Enhancements over I class � larger issue size, quad-threaded, up to 16 cores, burst freq up to 3 Ghz,
  3. Bus/Fabric - Shakti NoC, AXI4

S class

  1. 64-bit superscalar, multi-threaded variant for desktop/server applications.
  2. 2-64 cores, crossbar/ring interconnect, segmented L3 cache
  3. RapidIO based external cache coherent interconnect for multi-socket applications (up to 256 sockets)
  4. Hybrid Memory Cube support, 4 channels
  5. Threaded Vector Processor Unit
  6. Coprocessors for Database acceleration, Security acceleration, Machine Learning
  7. Experimental variants will be used as test-bed for our Adaptive System Fabric project
  8. Variants with differentiated cores for running kernels and user space VMs.

H class

  1. 64-bit in-order/mildly OO, multi-threaded, HPC variant with 32-128 cores
  2. 512/1024 bit VPU
  3. Goal is 3-5 + Tflops (DP, sustained)

T class

  1. Experimental security oriented 128/64-bit cores
  2. tagged ISA, single address space option, decoupling of protection from memory management.

N class

  1. Experimental cores for network processing targeting at executing the P4 NP language. based on custom ISA extensions

Experimental accelerators

  1. Neuromorphic accelerators for AI and ML type applications
  2. Stochastic cores for low power, non-deterministic computing tasks. An HVEC and AOMedia video decoder will be the first target.
  3. Vector processor variants for - HPC, SDR cores for 5G modems/basestations, low power OFDM based SDR

SoC Fabrics

  1. Lightweight microcontroller bus
  2. Fabric for 2 - 128 cores. Topogies - ring+mesh hybrid
  3. Mesh fabric for HPC

Socket Interconnect

We are also developing a processor to processor, cache-coherent interconnect, to allow building of
multi-socket server systems.The interconnect is based on the RapidIO standard. We are investigating
a two tier scheme where a MOESI/MESIF style scheme is
used for 2-8 socket systems and a directory based scheme for larger configurations (max 256 sockets)

Design Approach

The approach is to built optimal (high performance) building blocks that can be shared among the variants and
then add variant specific IP blocks. The above variants are just canonical references and the Shakti family will
see variants that will be hybrids.

Where possible, we will also provide the Synopsys/Cadence and Xilinx/Altera synthesis results for each module.

Final versions will contain the full BSV code, the generated Verilog code, testbenches, verification IP and FPGA support files.

The SHAKTI effort is part of a larger effort to build complete systems. As part of this effort,
IIT-Madras is developing interconnects (optical and copper) based on Gen 3 (10/25G per lane) RapidIO and
a scale-out SSD storage system called lightsor (see
based on this interconnect. The final goal is to build a fabric called Adaptive System fabric
which will use a combination of Hybrid Memory Cubes and RapidIO to unify support for compute, networking and storage.

Current Status

Alpha versions of the I, C and E classes have been released publicly

The source repository is composed of 2 directories, the core sources and sources for the non-core IP blocks.
Design documents and standards referenced in the design are provided in the doc directory.


  1. G S Madhusudan (,
  2. V. Kamakoti (,
  3. Neel Gala (

For Generic Queries/Collaboration/Feedback :