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SIMICS Overview

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SIMICS – A Full System Simulator• Models disks, runs unaltered OSs etc.• Accuracy is high (e.g., pollution

effects factored in) • Simulates all benchmarks• Requires in-depth OS knowledge

– paging, scheduling, even sendmail!• Bottom line: System runs unmodified

instructions and code

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SIMICS – Features Snapshot• Multi-processor full system simulator• Processors are simulated at the

instruction-set level– Support for various ISAs, e.g., SPARC, x86,

PPC, ARM• Extensible

– Mix and match architectures with operating systems

– Facilitates gathering of timing information– Extensible instructions

• "bare bones" simulation possible

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Applications• Processor Design• MP architecture• OS Development and Emulation• Debugging• Memory hierarchy design

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SIMICS Architecture

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Breaking Down SIMICS• SIMICS Central

• High-level architecture specification

• Features– New device modules plug in to Simics framework– Simics API provides functions, interfaces, etc for

user extensions– Global time can be paused to inspect state– Access memory traffic or set breakpoints anywhere, – Checkpoint simulations– Timestamp user inputs

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SIMICS Central• Heterogeneous nodes can be connected

into a network using Simics Central– Synchronizes virtual time – Distributes simulated traffic between nodes

• Imposes a minimum latency on all messages

• Network simulation speed is limited by the slowest process

• Currently supports Ethernet networks

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Memory and I/O• Users can extend a simulated memory

space by adding a timing model (such as Ruby)

• Simple cache models can be added to the base simulator

• Device models supported extensively– Keyboard/mouse controller, DMA, Interrupt

controller, floppy controller, Graphics cards, etc.– Users can write new device models

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Event Handling• Simics can mix event-driven and

time-driven components– step queue and time queue

• step queue pc steps• time queue resolution clock

cycle

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SIMICS Slowdown• Best case 10X - 100X

– Limited statistics• Cache 1000X - 10000X

– in-order processor• Processor 10000X - 1million

– cycle-accurate• Implication choose simulations

wisely

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References• Micro 35 Tutorial:

http://www.cs.pitt.edu/~cho/cs2410/currentsemester/handouts/simics_tutorial.pdf

• http://www.artes.uu.se/events/summer01/magnusson2001-08-24.pdf