Path: utzoo!mnetor!tmsoft!torsqnt!news-server.csri.toronto.edu!cs.utexas.edu!swrinde!zaphod.mps.ohio-state.edu!rpi!uupsi!sunic!isgate!krafla!thsa
From: thsa@rhi.hi.is (Thorvaldur S Arnarson)
Newsgroups: comp.sys.acorn
Subject: Re: MODE 21 & MULTISYNC
Message-ID: <2565@krafla.rhi.hi.is>
Date: 22 Dec 90 06:57:01 GMT
References: <1990Dec21.031201.3334@odin.diku.dk>
Reply-To: thsa@rhi.hi.is (Thorvaldur S Arnarson)
Organization: University of Iceland (RHI)
Lines: 16

The problem with mode 21 is that it eats upp nearly all of the memory badwith
and leaves little left for the precessor.  When the diskdrive issues an NMI
(non maskable interupt) for a slow flopy read the screen just doesn't get
the bandwith it takes to display the screen and hence goes blank.

This is roughly what happens, I don't know if the OS has a built in feature
to turn all screen DMA's off during interrupts that might might cause it
not to be fully redrawn, or if the harware behaves in such a civiliced manner.


Greetings,
    Thorvaldur S. Arnarson.

-- 
  Regards,
  Thorvaldur S. Arnarson