From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stas Sergeev Subject: Re: please explain to me why video/bios shadowing must be disabled to use graphics... -- Victory!!! Date: Thu, 17 Oct 2002 19:58:47 +0400 Sender: linux-msdos-owner@vger.kernel.org Message-ID: <3DAEDE37.7050208@yahoo.com> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: List-Id: Content-Type: text/plain; charset="us-ascii"; format="flowed" To: linux-msdos@vger.kernel.org Hello. Bart Oldeman wrote: >> slower than xdos... why ioperm() doesn't allow >>>0x3ff ports?.. > Once upon a time Linus decided that a 128 byte per-process i/o bitmap > is ok, but 8192 bytes is excessively large. Yes, and there was a reason then, which was that ISA had 10-bit IO space most likely, but why it wasn't altered since, is still unclear. > see also iopl(2) I don't think it can be used. Even if I trap int10, do iopl(3), then trap iret and do iopl(0), it is still dangerous, because pesky vbios calls some other ints in a mean time. iopl() is used in ports.c anyway to access that ports... I think there is no way around: VESA in WinXP have the same speed (which means that they also doesn't have an ability to manipulate the large IO bitmap? - strange).