Re: [gem5-users] simObject clocks and global simulation clock

[Andreas Hansson via gem5-users]

Hi Anny,

The short answer: there is no global “clock” in gem5

The long answer: There is a global absolute time in gem5, and it is measured in 
the abstract unit “Ticks”, defaulting to 1 ps. Do not think of Ticks as clock 
cycles. Instead, it is effectively the resolution of a digitised continuous 
time scale that everyone agrees on. 10 Ticks is the same to every object, just 
like 50 ns is the same.

The clocks in the different objects are used to enable us to express time 
(throughput and latency) in cycles. For example, a module might have a delay of 
3 Cycles, and that then gets translated to a absolute time (Ticks) by 
multiplying with the current clock of the clock domain. Thus, what a cycle 
means is different for different objects, and also possibly changing over time. 
At run time we turn relative time in cycles into absolute time when 
scheduling/executing events in the system.

I hope that answers your question.

Andreas

From: Vanchinathan Venkataramani via gem5-users 
<gem5-users@gem5.org<mailto:gem5-users@gem5.org>>
Reply-To: Vanchinathan Venkataramani 
<dcsv...@gmail.com<mailto:dcsv...@gmail.com>>, gem5 users mailing list 
<gem5-users@gem5.org<mailto:gem5-users@gem5.org>>
Date: Tuesday, December 16, 2014 at 4:04 PM
To: Anny <anya.k...@gmail.com<mailto:anya.k...@gmail.com>>, gem5 users mailing 
list <gem5-users@gem5.org<mailto:gem5-users@gem5.org>>
Subject: Re: [gem5-users] simObject clocks and global simulation clock

Ticks is the basic unit of time in gem5.  gem5 uses this for synchronization. 
Every system cycle is made up of n number of ticks ticks.


For a system unit with frequency = 2 GHZ, one cycle = 500 ticks

On Tue, Dec 16, 2014 at 7:04 PM, Anny via gem5-users 
<gem5-users@gem5.org<mailto:gem5-users@gem5.org>> wrote:
Hi all,

I have a question about clocks on gem5. In gem5, it seems that there is a
global simulation clock and every simObject has a clock domain. The eventq
is sorted in time. When two objects with two different clocks schedule two
events on eventq, how the order is determined since the two objects have
different clocks? Are all objects synchronious? it seems that everything in
the system is based of one clock (global simulation clock)? It is binding.


Best,
Anny.

_______________________________________________
gem5-users mailing list
gem5-users@gem5.org<mailto:gem5-users@gem5.org>
http://m5sim.org/cgi-bin/mailman/listinfo/gem5-users

-- IMPORTANT NOTICE: The contents of this email and any attachments are 
confidential and may also be privileged. If you are not the intended recipient, 
please notify the sender immediately and do not disclose the contents to any 
other person, use it for any purpose, or store or copy the information in any 
medium. Thank you.

ARM Limited, Registered office 110 Fulbourn Road, Cambridge CB1 9NJ, Registered 
in England & Wales, Company No: 2557590
ARM Holdings plc, Registered office 110 Fulbourn Road, Cambridge CB1 9NJ, 
Registered in England & Wales, Company No: 2548782
_______________________________________________
gem5-users mailing list
gem5-users@gem5.org
http://m5sim.org/cgi-bin/mailman/listinfo/gem5-users