This paper describes NSF-supported work in parallelized computer system simulators being done in the Electrical and Computer Engineering Department at the University of Texas at Austin. Our work is currently following two paths: (i) the FAST simulation methodology[9, 11, 10] that is capable of simulating complex systems accurately and quickly (currently about 1.2MIPS executing the x86 ISA, modeling an out-of-order superscalar processor and booting Windows XP and Linux) and (ii) the RAMP-White (White)[1, 22] platform that will soon be capable of simulating very large systems of around 1000 cores. We plan to combine the projects to provide fast and accurate simulation of multicore systems.

Over the past three and a half years, we have been working on defining and developing FPGAAccelerated Simulation Technologies (FAST)[2], [3], [4], [5], a novel methodology that uses FPGAs to build very fast simulators of complex computer systems. We have built a prototype that simulates the x86 ISA, boots Windows XP and Linux and runs unmodified applications at an average of 1.2MIPS, with the expectation of being able to run significantly faster. This talk describes some of the issues that we ran into while building our prototype and how we addressed them. It also describes areas where things worked out right, either due to foresight or blind luck.

This paper describes FAST, a novel simulation methodol- ogy that can produce simulators that (i) are orders of mag- nitude faster than comparable simulators, (ii) are cycle- accurate, (iii) model the entire system running unmodified applications and operating systems, (iv) provide visibility with minimal simulation performance impact and (v) are capable of running current instruction sets such as x86. It achieves its capabilities by partitioning simulators into a speculative functional model component that simulates the instruction set architecture and a timing model com- ponent that predicts performance. The speculative func- tional model enables the simulator to be parallelized, im- plementing the timing model in FPGA hardware for speed and the functional model using a modified full-system simu- lators. We currently achieve an average simulation speed of 1.2MIPS running x86 applications on x86 Linux and Win- dows XP and expect to achieve 10MIPS over time. Such simulators are useful to virtually all computer system sim- ulator users ranging from architects, through RTL design- ers and verifiers to software developers. Sharing a common simulation/design infrastructure could foster better commu- nication between these groups, potentially resulting in bet- ter system designs.

This paper describes the FAST methodology that enables a single FPGA to accelerate the performance of cycle-accurate computer system simulators modeling modem, realistic SoCs, embedded systems and standard desktop/laptop/server computer systems. The methodology partitions a simulator into (i) a functional model that simulates the functionality of the computer system and (ii) a predictive model that predicts performance and other metrics. The partitioning is crafted to map most of the parallel work onto a hardware-based predictive model, eliminating much of the complexity and difficulty of simulating parallel constructs on a sequential platform. FAST conventions and libraries have been designed to make creating, modifying, using and measuring such simulators straightforward. We describe a prototype FAST system: a full-system, RTL-level cycle-accurate-capable computer system simulator that executes the x86 ISA, boots unmodified Linux and executes unmodified x86 applications. The prototype runs two to three orders of magnitude faster than the fastest Intel and AMD RTL-level cycle-accurate x86 software-based simulators and about six to seven times faster than RTL simulation.

This paper describes the FAST methodology that enables a single FPGA to accelerate the performance of cycle-accurate computer system simulators modeling modern, realistic SoCs, embedded systems and standard desktop/laptop/server computer systems. The methodology partitions a simulator into (i) a functional model that simulates the functionality of the computer system and (ii) a predictive model that predicts performance and other metrics. The partitioning is crafted to map most of the parallel work onto the hardware-based predictive model, eliminating much of the complexity and difficulty of simulating parallel constructs on a sequential platform. FAST conventions and libraries have been designed to make creating, modifying, using and measuring such simulators straightforward. We describe a prototype FAST system: a full-system, RTL-level cycle- accurate-capable computer system simulator that executes the x86 ISA, boots unmodified Linux and executes unmodified x86 applications. The prototype runs two to three orders of magnitude faster than RTL-level cycle-accurate x86 software-based simulators and about six to seven times faster than RTL simulation.