AFAIK you can also re-distribute DirectX (but I don't think you can
re-distribute SP2) and thus have the app prompt and install it, but
the downside is that you'd catch all the support calls when this
breaks on old drivers, etc.
I will do that. But often thats enough to put off some people who might
otherwise be your customer. Particularly the people who don't even know what
DirectX is. I want my product to work on 90% of all XP machines out there
without having to install extra stuff - but I also want to use the latest
technology that will be available on those 90% of computers.
You may hit other walls, and the devil is in the details. For
example, you'd want to avoid being locked into nVidia and ATi, and be
able to run on integrated graphics too.
If non-gaming users balk at a new DirexctX, they are likely to flat
out refuse to buy a costly SVGA card for your app.
Here's a case of "the devil is in the details"; a game used
PixelShader 1.1, yet claimed to work with a low spec such as "Pentium
II 400MHz, 128M RAM, GeForce 2" etc.
However, the "budget" GeForce 4 cards (which may account for 75% of
"GeForce 4" sales) don't support PixelShader 1.1, so they got their
ass kicked by folks with (say) Pentium 4 2GHz, 512M RAM, budget
GeForce 4, along with those using integrated graphics of course.
"How the folk am I supposed to know what 'PixelShader 1.1' is??"
So if you're using a high-version DirectX, be careful the feature set
you require is not far more restrictive than the SP level.
The other questions are:
1) When do you plan to come to market?
The later, the less of an issue XP SP2 will be. I really hope you're
doing your homework on Vista compatibility, BTW.
2) Does your app require Internet access?
If it does, especially if it needs bband, then you'd be fair in
demanding SP2, as by the time you ship, it will be the only XP SP
level that is supported, and thus patched, and thus safe for Internet
use. You'd just require SP2, and that's it.
If it doesn't, then there may be a large hidden mass of pre-SP2 system
you could sell to, that don't have a burning need SP2 for safety, and
that won't be counted in any of the Internet-polled statistics.
Simply getting the huge wad of SP2 to a PC is a challenge that most
users may fail or decline, if they are not on bband Internet access.
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The most accurate diagnostic instrument
in medicine is the Retrospectoscope