From: Serge Golovin Message-Id: <199701131202.PAA03194@marstu.mari.su> Subject: Re: Low-level access To: mmastrac AT acs DOT ucalgary DOT ca (Matthew Mastracci) Date: Mon, 13 Jan 1997 15:02:40 +0300 (MSK) Cc: djgpp AT delorie DOT com (DJGPP Mailing List) In-Reply-To: from "Matthew Mastracci" at "Jan 12, 97 00:57:48 am" MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Matthew Mastracci wrote: > From my understanding, > any program not running at ring-0 invokes an exception error with port > I/O? Wrong. It completely depends on your PM manager and how it sets up port I/O map. If PM needs to control certain ports it will set proper bits in this map and you'll get exceptions. If not - you'll run clear. Yes, there is additional overhead in processing your in and out instructions while you're in protected mode. But this is "hardware" overhead. Processor has to check I/O map everytime it does in/out. This promlem slightly solved by chaching TS segments, ehich is done in majority of processors. > I believe I know the fastest way to to access my graphics memory, > but as I'll be needing the port accesses to go hand-in-hand with the > memory accesses, I'd like to know the fastest way to do it. Thanks in > advance, What _exactly_ aree you trying to do? -- SerGo, aka RES