Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!seismo!rutgers!ames!ucbcad!ucbvax!jade!eris!mwm From: mwm@eris.BERKELEY.EDU (Mike (Don't have strength to leave) Meyer) Newsgroups: comp.sys.amiga Subject: Re: Amiga Multi-tasking Overhead Message-ID: <1806@jade.BERKELEY.EDU> Date: Tue, 2-Dec-86 20:59:50 EST Article-I.D.: jade.1806 Posted: Tue Dec 2 20:59:50 1986 Date-Received: Wed, 3-Dec-86 09:23:02 EST References: <1986Dec2.102542.4658@utcs.uucp> Sender: usenet@jade.BERKELEY.EDU Reply-To: mwm@eris.BERKELEY.EDU (Mike (Don't have strength to leave) Meyer) Organization: Missionaria Phonibalonica Lines: 25 In article <1986Dec2.102542.4658@utcs.uucp> wagner@utcs.uucp (Michael Wagner) writes: > >I've heard it said on the net that, when idling, an Amiga is using about 17% >of the CPU (at least in my case, the numbers seem worse, but that's another >problem). I've also heard it said that this is the price for multi-tasking. > >The more I think about this, the less likely it seems. People have often >criticized large mainframe operating systems like MVS for using up 3 or 4 >% when idling. In MVS's case, there is a small amount of timer-interrupt >driven performance monitoring going on all the time. In the case of the >Amiga, some work is being done every vertical retrace time, to set up the >copper. But 17%? ... One thing to remember - 3 or 4 % of a 3081 or 3090 is a *LOT* more CPU than 17% of an Amiga (or maybe even 100% of an Amiga!). The larger the CPU, the less you expect to spend on system overhead. For instance, 17% for 4.2BSD on a VAX 750 is high, but not outrageous. The same figures on an VAX 8800 are bad enough to call for firing a system manager. For the Amiga, 17% is high enough that someone should explain it, then fix it. The Amiga CPU is about the same as a 750, but the OS is doing a lot less, and so should have correspondingly lower overhead.