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From: Simon Johnston <skj@ACM.ORG>
Subject: Re: Port I/O
Date: 1996/11/13
Message-ID: <01BBD13B.2E702E00@idc213.rb.icl.co.uk>#1/1
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sender: Ada programming language <INFO-ADA@LISTSERV.NODAK.EDU>
comments: Gated by NETNEWS@AUVM.AMERICAN.EDU
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newsgroups: comp.lang.ada
Date: 1996-11-13T00:00:00+00:00
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I think the comments on NT are a little unfair, we are using it in a =
high-speed near real-time mission critical environment (150+ lane =
hypermarkets) where throughput is very much dependant on O/S =
performance. In this environment we have had to develop our own NT =
drivers for some hardware and make use of a number of other facilities, =
we also have a good relationship with the NT guys in Redmond.
As far as the game SDK is concerned I again question the comment on =
price, I got two copies free with our MSDN subscription (if your =
developing MS based software without MSDN you deserve everything you =
don't get!) and I'm sure if you talk nicely to MS they can get you a =
copy. With the game SDK Windows 95 and Windows NT have full DirectX, =
DirectSound, DirectDraw, DirectPlay etc. which do provide port level =
access to the hardware, fast enough for game programming.=20
As far as industrial control is concerned then I think you should be =
talking directly with Redmond as there is quite a push to get NT into =
this area.

Michael F Brenner wrote:
> Ed Falis of Thomson Software Products 617 221-7341 said:
>  > you might ask yourself
>  > why you're trying to do what you're doing (presumably direct =
hardware
>  > manipulation) from user code under NT or W95 rather than going =
through
>  > a device driver.
>=20
> The obvious answer is that NT does not provide device drivers, or
> fast enough device drivers to do the kind of animation, serial =
control,
> parallel control, disk access, and sound that the games, simulatons, =
and
> robots we are building require. Extremely high level operating systems
> have advantages for some types of software (like databases where speed
> is not important). However, when controlling industrial or game =
processes,
> you need much faster access to the bits of information (like pixels,
> voxels, serial bits, and control bytes) than is possible with a =
four-level
> security layer on top of an operating system kernel. The game =
developer
> need to be able to by-pass the operating system whenever anything
> interesting in the game needs to be programmed. As an example, in
> writing software that displays a map, even a background map, you need
> direct hardware access to the memory mapped pixel in order to display =
it
> fast enough that the user does not have to wait for it, and even then,
> you have to carefully control the order of the bits and bytes you =
display,
> in order to gradually res and de-res the map up, to make up for the
> extremely low bandwidth of current CRT-type displays. Until operating
> systems realize this (as Windows NT 4 is beginning to, by granting
> programmers a little bit of access to the pixels and some ports if =
they
> buy an expensive game developers kit), programmers must resort to
> some not very nice practices in order to meet the performance =
requirements
> of the software.
>=20
>=20
with StandardDisclaimer; use StandardDisclaimer;
package Sig is
--,----------------------------------------------------------------------=
---.
--|Simon K. Johnston - Technical Architect  (C++/Ada95) |ICL Retail =
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Place   |
--|Internet : skj@acm.org                               |51 Bath Road    =
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end Sig;