PC grahpics card questions

[Volpe, Christopher R (CRD)]

Hi folks-
  I'm in the market for a new graphics card, mainly for doing vtk-related work,  for my home PC, an
AMD K6-233-based system (no AGP slot) running NT4. My current card is a Diamond Stealth 64 Video VRAM
with 2MB of memory and no 3D acceleration whatsoever. I'm not necessarily looking for the best 3D
graphics available, but rather the best combination of 2D performance and 3D performance. I'm looking
for a PCI card under $150 that can do at least 1280x1024x32bpp at 70Hz (I can still see flicker at
60Hz and it makes my eyes tired). I'd like it to be able to do 3D dubble-buffered with Z-buffering at
that resolution as well. Obviously, NT support is mandatory. Number of triangles per second is of
secondary importance, after the previous requirements. And game-centric features like fog, great
texture implementation, etc are of much less importance. Any recommendations would be appreciated.

Two Questions:
1) Since 2D performance is important to me, I'm wondering if I should pay a few extra bucks for cards
that have the more expensive SGRAM as opposed to the ordinary SDRAM. Unfortunately, I haven't been
able to find any cards with (dual-ported) VRAM that meet my requirements. Any thoughts? 

2) While browsing a couple of vendor sites, I came across ATI's "Xpert98" card, with 8MB of memory.
Although it seems to be really fond of Windows 98, it does claim to support Windows NT 4.0. It also
claims to be  able to do 1280x1024 with 16.7M colors while using double buffering and z-buffering (16
bit). I'm wondering how this is possible with 8MB. Given 4 bytes per pixel in each the front and back
buffers, and another 2 bytes of Z buffer per pixel, yields 10 bytes per pixel, which at 1280x1024
requires 12.5 MB of memory. Even if they cram the RGB into 3 bytes (which, in my experience, results
in a severe 2D performance degradation due, I presume,  to the pixels not being word-aligned), you
need 8 bytes per pixel or 10MB or graphics memory. I don't see how they do it with 8MB. Do they cheat
and use system memory for the Z buffer? Any insights?

thanks in advance,


Chris
________________________________________
Christopher R. Volpe
Computer Scientist
Computer Graphics & Systems Program
GE Corporate Research & Development
Bldg KW, Room C215
P.O. Box 8, Schenectady, NY 12301

e-mail: volpecr at crd.ge.com    
web: http://www.crd.ge.com/~volpecr
(518) 387-7766, Dial Comm: 8*833-7766, Fax: (518) 387-6981




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