[CST-2] Comp. Sys. Modelling

[Chris Applegate]

> > CSM - 2000P9Q7
> >
> > Has anyone done this. If so...I have a couple of queries...
> >
> > Second part - can we give a numerical value to this? Since
> the bounds of
> > a balanced machine depend on utility, which depends the number of
> > customers, then I can only give a formula answer of 10N/(3+N) &
> > 40N/(3+N) as the bounds...
>
> The first bound provided by giving all devices Dav, so the
> max throughput is
> 1/Dav = around 18.6 transactions/s
>
> The second provided by giving as many devices Dmax as
> possible, so the max
> throughput is 1/Dmax = 10 transactions/s

But that doesn't take into account N or K, which I think it needs to as
you'll need to queue for other customers to finish with the device
you're waiting for first - it's taken into account in the notes when it
considers the optimistic/pessimistic cases like you said, so we get  X =
N/(N+3) x 1/Dav or 1/Dmax.

There must be more to it than that, I can't believe that inverting two
numbers is worth 7 marks...

Cheerio,

Chris
do something lastminute.work

Chris Applegate
Room X6, Corpus Christi College, Cambridge, CB2 1RH
chris@qwghlm.co.uk / www.qwghlm.co.uk / [Redacted by SRCF sysadmins on request]
ICQ 41706821          PGP key available on request