VMD-L Mailing List

From: John Stone (johns_at_ks.uiuc.edu)
Date: Sat Jun 08 2002 - 23:45:47 CDT

Dear Christian,
  I can't address the question of whether or not it only makes a
difference when using an external monitor, as I have no first-hand
knowledge there, but I can address a couple other points you asked
about:
  1) The 1MB level 3 cache would definitely help VMD (all versions
     current and future...)
  2) The 32MB of video memory would not help past versions of VMD,
     as they use software-based rendering with Mesa. We are working
     on getting VMD running using the native MacOS X OpenGL libraries
     and using the native MacOS X interface instead of XFree86. When
     this new native version is complete, VMD will take advantage of
     the OpenGL hardware acceleration (if any) available on the machine.
     This being the case (native OpenGL that is), the major advantages
     gained by having more video memory are typically:
       - higher resolution video modes (on laptops with monitor outs,
         this would allow you to run dual screen mode in nice high-res modes)
       - deeper color depths (32-bit color and at high res)
       - extra OpenGL buffers (stencil, overlay planes, accumulation buffer),
         and much more available texture memory, which is used when rendering
         EDM files, potential maps, etc in VMD.

I assume that the Radeon 7500 is probably also faster than the regular
one, so since VMD's performance is typically bound by vertex processing
speed (T&L speed specifically) rather than fill-rate, you will want to
consider whether the 7500 offers higher triangle rates than the non-7500
version does.

You might want to consider what other applications you'll be running
and base your decision off of the mix of apps and how important it will
be to you to have peak performance or not. After all, if you're just working
with very small molecules, you won't really NEED the fastest machine,
its only an issue if you intend this laptop to be a "desktop replacement"
where you'll do most of your work on it. If that's what you have in mind,
then it might be good to splurge on the better hardware, but that's a
choice you'll have to make, I know these things aren't cheap...

I'm making progress on getting us closer to having a native build of VMD
for MacOS X, but we've still got a few more things to work out before
we've got one really running. I'll announce to VMD-L as soon as we have
a test version available.

Thanks for using VMD,
  John Stone
  vmd_at_ks.uiuc.edu

On Thu, Jun 06, 2002 at 12:06:20AM +0200, Christian Simon wrote:
> Dear List,
>
> I would like to buy an Apple G4 Titanium laptop. Considering my budget,
> I have the choice to buy:
> -either the one with 667MHz proc, 1 Mb level 3 cache, 32 Mb video card
> (ATI Mobility Radeon 7500), 256 Mb RAM,
> -either the one with 667MHz proc, no lvl 3, 16 Mb video card
> (ATI Mobility Radeon) 512 Mb ram.
>
> The guys at the shop told me I would not see the difference on the
> laptop screen, but only on external high resolution devices, and
> consequently advise me to buy the cheapest one ! I would like to believe them...
>
> The way VMD is implemented, would it make any difference ?
> Has anyone experience with these laptops ?
> --
> Christian SIMON
> The Center for Molecular Modeling (CMM, Rm. 141I)
> University of Pennsylvania, Tel: (215)-573-4773
> Department of Chemistry, Box 127 Fax: (215)-573-6233
> 231 S. 34th St.
> Philadelphia, PA 19104-6323 USA 

-- 
NIH Resource for Macromolecular Modeling and Bioinformatics
Beckman Institute for Advanced Science and Technology
University of Illinois, 405 N. Mathews Ave, Urbana, IL 61801
Email: johns_at_ks.uiuc.edu                 Phone: 217-244-3349              
  WWW: http://www.ks.uiuc.edu/~johns/      Fax: 217-244-6078