1/1/2024 0 Comments Idle pc gns3![]() So there are no idle states – dynamips just screams through those instructions one at a time around and around – except that there will be many, many places where the instruction that is executed is one that changes the program counter, causing dynamips to extract the instructions in a non-linear sequence.Īnd some of those instructions will be be in little groups where the emulated router is sitting in an idle state – as in waiting for a packet to arrive or a key to be pressed at the console. The basic logic is something like this: Set the program counter (PC) to 1 It takes a binary image of MIPS machine code and interprets each instruction one at a time and then executes that instruction on the host computer. However dynamips is a different kind of program. Or for a timer to expire to remind it to send a message. To understand the dynamips/GNS3 Idle-PC concept, you have to start by looking at the way software operates.Ī normal piece of software generally has one or more places in the code where the program just sits in an “idle” loop – say waiting for a key press. When emulator has visits this PC value Idle-Max times, it suspends itself for Idle-Sleep ms to allow other processes to get on their tasks. The Idle-PC is a guess at where the Program Counter might be pointing to an idle-loop in the emulated router. ![]() Without an Idle-PC set, dynamips attempts to emulate instructions one at a time as fast as it can, consuming up to 100% of the available CPU. ![]() I have to admit that I’d I had only a vague idea of what was happening when I wrote this post on the GNS3 forum, but recently I decided I had to nail it. Firstly let me say thanks to Jeremy Grossmann (principal programmer for GNS3) for helping me finally get my head around this concept. ![]()
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