CISC, RISC, OISC

To the present day, the performance of microprocessors has progressed dramatically. Recently, almost all computer systems use reduced instruction set computer (RISC) architectures. However, about 30 years ago, complex instruction set computer (CISC) architectures were widely used for almost all computer systems. The advantages and successes of RISC architectures are attributable to their simplified structures. Conventional complex instruction set computer (CISC) architectures invariably included various and numerous instruction sets. Each instruction was able to execute a complicated multi-step operation. For that reason, the CISC architectures were useful in assembler-based programming environments and in systems with small amounts of memory. However, such complicated architectures prevent increases in clock frequency or a processor’s processing power. Therefore, RISC architectures—which use simple architectures based on single-step instruction sets—have been developed. The RISC architectures present advantages in terms of higher clock frequency, smaller implementation area, and lower power consumption than conventional complex instruction set computer (CISC) architectures. Observation of many examples reveals that, in circuit implementations, a simple structure is best to increase the overall performance. That principle is also applicable to programmable devices. If clock-by-clock reconfigurable devices are used, even a single instruction set computer (SISC) can be implemented onto them. A single instruction set computer is one in which a processor has only a single instruction. During production, various single instruction set computers are prepared: a single instruction set computer with an AND logic function, a single instruction set computer with an adder function, and so on. These processor units are implemented at necessary times and at necessary places of a programmable device. In CISC and RISC architectures, the hardware is fixed. Its operations are switched using software commands, as portrayed in Fig. 1(a). In contrast, in a single instruction set computer, the operation changes are executed by hardware reconfigurations, as shown in Figs. 1(b) and 1(c). Therefore, in a single instruction set computer, a processor with a certain function itself can be reconfigured to another processor with another function. The implementation of such single instruction set computers provides the following advantages under programmable device implementations. A single instruction set computer with the simplest architecture can operate at the highest clock frequency among all processor architectures. In RISC architectures, many selectors to change functions are implemented; such selectors have a certain delay. However, single instruction set computers

We describe a novel architectural framework that allows software applications written for a given Complex Instruction Set Computer (CISC) to migrate to a different, higher performance architecture, without a significant investment on the part of the application user or developer. The framework provides a hardware mechanism for seamless switching between two instruction sets, resulting in a machine that enhances application performance while keeping the same program behavior (from a user perspective). High execution speed on migrated applications is achieved through automated translation of the object code of one machine to that of the other, using advanced global optimization and scheduling techniques. Issues affecting application behavior, such as precise exceptions, as well as self-modifying code, are addressed. Relaxation of full compatibility on these issues lead to further possible performance gains, encouraging applications to adopt the newer architecture.The proposed framework offers a path for moving from complex instruction set computers (CISCs) to newer architectures, such as reduced instruction set computers (RISCs), superscalars, or very long instruction word (VLIW) machines, while protecting the extensive economic investment represented by existing software. To illustrate our approach, we show how system code written (and compiled) for the IBM System/390 can yield fine-grain parallelism, as it is targeted for execution by a VLIW machine, with encouraging performance results.

1 - Complex instruction set computers

The evolution of computer architecture has given rise to two main approaches: RISC (Reduced Instruction Set Computer) and CISC (Complex Instruction Set Computer). These architectures differ significantly in terms of instruction design, efficiency, and performance. This study aims to analyze the performance and efficiency of RISC and CISC in the context of computer architecture organization. The methodology includes a literature review, comparative analysis, and performance evaluation based on parameters such as processing speed, power consumption, and design complexity. The results indicate that RISC tends to be more efficient in terms of power consumption and execution speed for simple instructions, while CISC excels in handling complex instructions with fewer lines of code. The findings of this study can serve as a reference for the development of modern computer architectures that balance performance and efficiency.

The single or one instruction set computer (OISC, pronounced, “whisk”) is the penultimate reduced instruction set computer (RISC)1. In OISC, the instruction set consists of one instruction, and then by the orthogonality of the instruction along with composition, a complete set of operations is synthesized. This approach is completely opposed to a complex instruction set computer (CISC), which incorporates many complex instructions as microprograms within the processor.

This work presents the proof of concept implementation for the first hardware-based design of Moving Target Defense over IPv6 (MT6D) in full Register Transfer Level (RTL) logic, with future sights on an embedded Application-Specified Integrated Circuit (ASIC) implementation. Contributions are an IEEE 802.3 Ethernet stream-based in-line network packet processor with a specialized Complex Instruction Set Computer (CISC) instruction set architecture, RTL-based Network Time Protocol v4 synchronization, and a modular crypto engine. Traditional static network addressing allows attackers the incredible advantage of taking time to plan and execute attacks against a network. To counter, MT6D provides a network host obfuscation technique that offers network-based keyed access to specific hosts without altering existing network infrastructure and is an excellent technique for protecting the Internet of Things, IPv6 over Low Power Wireless Personal Area Networks, and high value globally routable IPv6 interfaces. This is done by crypto-graphically altering IPv6 network addresses every few seconds in a synchronous manner at all endpoints. A border gateway device can be used to intercept select packets to unobtrusively perform this action. Software driven implementations have posed many challenges, namely, constant code maintenance to remain compliant with all library and kernel dependencies, the need for a host computing platform, and less than optimal throughput. This work seeks to overcome these challenges in a lightweight system to be developed for practical wide deployment.

Those who design high-performance architectures today must design machines in such a way that compiler technology can exploit the power of their architectures—often through parallelism at many different levels. Moreover, new compiler concepts and techniques are needed to cope with rapidly advancing hardware technology. In fact, recent architectural breakthroughs have been directly related to innovative compiler optimizations—whether it be for reduced instruction set computers (RISC), complex instruction set computers (CISC), multiprocessing, or vector processing.KeywordsSignal CapacityInstruction ScheduleSoftware PipelineCompiler OptimizationMachine CycleThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

In this paper, we present the characterization and design of energy-efficient, on chip cache memories. The characterization of power dissipation in on-chip cache memories reveals that the memory peripheral interface circuits and bit array dissipate comparable power. To optimize performance and power in a processor's cache, a multidivided module (MDM) cache architecture is proposed to conserve energy in the bit array as well as the memory peripheral circuits. Compared to a conventional, nondivided, 16-kB cache, the latency and power of the MDM cache are reduced by a factor of 1.9 and 4.6, respectively. Based on the MDM cache architecture, the energy efficiency of the complete memory hierarchy is analyzed with respect to cache parameters in a multilevel processor cache design. This analysis was conducted by executing the SPECint92 benchmark programs with the miss ratios for reduced instruction set computer (RISC) and complex instruction set computer (CISC) machines.

11 - The next generations

In this paper we concentrate on the effect of instruction set architecture on the performance potential of a computer system. These issues are key in considerations of what instruction set is most appropriate for the support of high level languages on general purpose machines. Two possible approaches are so called complex instruction sets, such as those of the VAX and IAPX 432, and the “reduced” instruction set of the RISC I [2] microcomputer, which is expected to have performance similar to that of a VAX 11-780. We propose a method of instruction set interpretation that takes advantage of the architectural features of complex instruction sets. These methods have been simulated executing real programs and in the case of the VAX instruction set have resulted in a typical improvement of a factor of two, assuming the same cycle time as the VAX 11-780. The techniques presented exploit the context available in a complex instruction and retain this information for use in subsequent execution of that instruction. Since this context is available only within a single instruction, low level instruction sets cannot benefit from this technique. In this sense the reduced instruction set machines as implemented in RISC are at their architectural limits, while complex instruction sets such as the VAX are far from theirs. For these reasons, complex instruction sets can have a significantly greater performance potential than a RISC instruction set for a given technology.

Instruction-set architecture (ISA) simulators are an integral part of today's processor and software design process. While increasing complexity of the architectures demands high-performance simulation, the increasing variety of available architectures makes retargetability a critical feature of an instruction-set simulator. Retargetability requires generic models while high-performance demands target specific customizations. To address these contradictory requirements, we have developed a generic instruction model and a generic decode algorithm that facilitates easy and efficient retargetability of the ISA-simulator for a wide range of processor architectures, such as RISC, CISC, VLIW, and variable length instruction-set processors. The instruction model is used to generate compact and easy to debug instruction descriptions that are very similar to that of architecture manual. These descriptions are used to generate high-performance simulators. Our retargetable framework combines the flexibility of interpretive simulation with the speed of compiled simulation. The generation of the simulator is completely separate from the simulation engine. Hence, we can incorporate any fast simulation technique in our retargetable framework without introducing any performance penalty. To demonstrate this, we have incorporated fast IS-CS simulation engine in our retargetable framework which has generated 70% performance improvement over the best known simulators in this category. We illustrate the retargetability of our approach using two popular, yet different, realistic architectures: the SPARC and the ARM.

12 - The next generations

One potential disadvantage of a machine with a reduced instruction set is that object programs may be substantially larger than those for a machine with a richer, more complex instruction set. The main reason is that a small instruction set will require more instructions to implement the same function. In addition, the tendency of RISC machines to use fixed length instructions with a few instruction formats also increases object program size. It has been conjectured that the resulting larger programs could adversely affect memory performance and bus traffic. In this paper we report the results of a set of experiments to isolate and determine the effect of instruction set complexity on cache memory performance and bus traffic. Three high-level language compilers were constructed for machines with instruction sets of varying degrees of complexity. Using a set of benchmark programs, we evaluated the effect of instruction set complexity had on program size. Five of the programs were used to perform a set of trace-driven simulations to study each machine's cache and bus performance. While we found that the miss ratio is affected by object program size, it appears that this can be corrected by simplying increasing the size of the cache. Our measurements of bus traffic, however, show that even with large caches, machines with simple instruction sets can expect substantially more main memory reads than machines with dense object programs.

One potential disadvantage of a machine with a reduced instruction set is that object programs may be substantially larger than those for a machine with a richer, more complex instruction set. The main reason is that a small instruction set will require more instructions to implement the same function. In addition, the tendency of RISC machines to use fixed length instructions with a few instruction formats also increases object program size. It has been conjectured that the resulting larger programs could adversely affect memory performance and bus traffic. In this paper we report the results of a set of experiments to isolate and determine the effect of instruction set complexity on cache memory performance and bus traffic. Three high-level language compilers were constructed for machines with instruction sets of varying degrees of complexity. Using a set of benchmark programs, we evaluated the effect of instruction set complexity had on program size. Five of the programs were used to perform a set of trace-driven simulations to study each machine's cache and bus performance. While we found that the miss ratio is affected by object program size, it appears that this can be corrected by simplying increasing the size of the cache. Our measurements of bus traffic, however, show that even with large caches, machines with simple instruction sets can expect substantially more main memory reads than machines with dense object programs.

Code size is becoming an important design factor in the embedded domain. To deal with this problem, many embedded RISC processors support a dual-width instruction set. Mixed code generation is also introduced in expectation of achieving both higher code density from the narrow instruction set (usually 16 bits) and good performance from the normal one (usually 32 bits), with little extra cost. To a certain application domain, processors can combine an efficient general purpose instruction set and a narrow instruction set tailored to the particular applications. Since the design of instruction set is highly related to the compiler and the application programs, a feedback driven technique will be a good choice. In this paper, we introduce a framework of automatic narrow instruction set design. The instructions are described in our Instruction Set Description Template (ISDT). Given a set of application programs, the design tool will iteratively use the suggested narrow instruction set represented in ISDT to do mixed-code generation and to update the narrow instruction set according to the evaluation feedback, thus to get an ultimate fine narrow instruction set without human designer's involvement. We describe our method in detail by example of designing narrow instruction set for UniCore with the mediabench as the application set, and show its usefulness through the experiments.