No instruction set computing

No instruction set computing (NISC) is a computing architecture and compiler technology for designing highly efficient custom processors and hardware accelerators by allowing a compiler to have low-level control of hardware resources.

Overview

NISC is a statically-scheduled horizontal nanocoded architecture (SSHNA). The term "statically scheduled" means that the operation scheduling and hazard handling are done by a compiler. The term "horizontal nanocoded" means that NISC does not have any predefined instruction set or microcode. The compiler generates nanocodes which directly control functional units, registers and multiplexers of a given datapath. Giving low-level control to the compiler enables better utilization of datapath resources, which ultimately result in better performance. The benefits of NISC technology are:

Simpler controller: no hardware scheduler, no instruction decoder
Better performance: more flexible architecture, better resource utilization
Easier to design: no need for designing instruction-sets

The instruction set and controller of processors are the most tedious and time-consuming parts to design. By eliminating these two, design of custom processing elements become significantly easier.

Furthermore, the datapath of NISC processors can even be generated automatically for a given application. Therefore, designer's productivity is improved significantly.

Since NISC datapaths are very efficient and can be generated automatically, NISC technology is comparable to high level synthesis (HLS) or C to HDL synthesis approaches. In fact, one of the benefits of this architecture style is its capability to bridge these two technologies (custom processor design and HLS).

History

In the past, microprocessor design technology evolved from complex instruction set computer (CISC) to reduced instruction set computer (RISC). In the early days of the computer industry, compiler technology did not exist and programming was done in assembly language. To make programming easier, computer architects created complex instructions which were direct representations of high level functions of high level programming languages. Another force that encouraged instruction complexity was the lack of large memory blocks.

As compiler and memory technologies advanced, RISC architectures were introduced. RISC architectures need more instruction memory and require a compiler to translate high-level languages to RISC assembly code. Further advancement of compiler and memory technologies leads to emerging very long instruction word (VLIW) processors, where the compiler controls the schedule of instructions and handles data hazards.

NISC is a successor of VLIW processors. In NISC, the compiler has both horizontal and vertical control of the operations in the datapath. Therefore, the hardware is much simpler. However the control memory size is larger than the previous generations. To address this issue, low-overhead compression techniques can be used.

External links

NISC Toolset (a C-to-Verilog and custom processor design tool) in CECS UC, Irvine

CPU technologies

Architecture	Von Neumann Harvard (Modified Harvard) Dataflow TTA

Instruction set	ASIP CISC RISC EDGE EPIC MISC OISC VLIW NISC ZISC TRIPS Comparison

Word size	1-bit 4-bit 8-bit 9-bit 10-bit 12-bit 15-bit 16-bit 18-bit 22-bit 24-bit 25-bit 26-bit 27-bit 31-bit 32-bit 33-bit 34-bit 36-bit 39-bit 40-bit 48-bit 50-bit 60-bit 64-bit 128-bit 256-bit 512-bit variable

Execution	Instruction pipelining Bubble Operand forwarding Out-of-order execution Register renaming Speculative execution Branch predictor Memory dependence prediction Hazards

Parallel level	Bit Bit-serial Word Instruction Scalar Superscalar Task Thread Process Data Vector Memory

Multithreading	Temporal Simultaneous Preemptive Cooperative

Flynn's taxonomy	SISD SIMD MISD MIMD SPMD Addressing mode

Types	Digital signal processor (DSP) GPGPU Microcontroller Physics processing unit System on a chip (SoC) Cellular

Components	Address generation unit (AGU) Arithmetic logic unit (ALU) Barrel shifter Floating-point unit (FPU) Back-side bus Multiplexer Demultiplexer Registers Memory management unit (MMU) Translation lookaside buffer (TLB) Cache Register file Microcode Control unit Clock rate

Power management	APM ACPI Dynamic frequency scaling Dynamic voltage scaling Clock gating

CPU hardware security	Non-executable memory (NX bit) Bounds checking (Intel MPX) Hardware restriction (firmware) Trusted Execution Technology Secure cryptoprocessor Hardware security module Hengzhi chip

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No instruction set computing

Overview

History

See also

Further reading

External links