Path: utzoo!attcan!uunet!microsoft!kevinro
From: kevinro@microsoft.UUCP (Kevin ROSS)
Newsgroups: comp.os.os2
Subject: Re: CodeView and OS/2 v1.1
Message-ID: <50025@microsoft.UUCP>
Date: 14 Feb 90 18:48:53 GMT
References: <6339@cps3xx.UUCP> <2333@dataio.Data-IO.COM>
Reply-To: kevinro@microsoft.UUCP (Kevin ROSS)
Distribution: na
Organization: Microsoft Corp., Redmond WA
Lines: 16

In article <2333@dataio.Data-IO.COM> bright@sauk.Data-IO.COM (Walter Bright) writes:
>I had the same problem. The incantation to fix it is to add the line:
>	IOPL=YES
>to your CONFIG.SYS. It seems that the kernel does not support debuggers,
>and still hardware has to be accessed directly.

The kernel supports debuggers using the DOSPTRACE facility. 
However, codeview needs to be able to access video memory directly, 
due to some potential deadlock problems when debugging a program that 
uses the VIOCALLS.DLL. 

That is why IOPL must be set to YES. 


Kevin Ross
microsoft!kevinro