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Guest Allan Jones

Frame rate observation Fly v X-Plane

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Yes, I'm still flying the same old Beige G3. As you know, I've spent most of my air time in X-Plane since upgrading to OSX. I gave up on solving the Fly! II control device problems under X and, frankly, can't remember the last time I booted into OS9.A few weeks ago, the GPU cooling fan on my Radeon started making ominous noises so I had it out for a few days. To keeping using X-Plane and some other apps that need more hardware acceleration than the on-board ATI Rage 64 chipset can provide, I reinstalled my old ATI Rage Orion 16MB vidcard while working out the problems with the Radeon fan.I used the Orion for beta-testing FlyII and until about 14 months ago, when I scored the Radeon 32MB. Back then, switching from the Orion to the Radeon had virtually no effect on FlyII frame rates, although I could set some of the view options a notch higher. (And, you old-timers may recall, upgrading my processor from 300 to 500 mHz had almost no effect on FlyII yet improved every other OpenGL program I had.) Downgrading to the older vidcard had an immediate and unpleasant effect on X-Plane.In X-Plane, you can set a minimum desired frame rate--default is 12.5 frames/sec. As the rates approach this setting, the sim starts cutting back on max vis distance to compensate; it does this on the fly--a cute trick. With this method, rates seldom reach the minimum except with very large aircraft with wild paint jobs. With the Radeon, in-cockpit rates with panel are around 17-18 fps (settings:1024x768; 32-bit color; "high" detail setting, which is, on a scale of 1 through seven, a four or five).When I installed the old Orion card, I reduced the detail setting one notch before running X-Plane. Even so, rates dropped precipitously to the 12.5 fps minimum, and likely less based on the choppiness. I reduced the detail setting even further and could not get good rates. As usually, setting color depth to 16-bit had no effect--this is said to be a characteristic of the ATI cards with many programs.Worried that something had gone dreadfully wrong with the installation, I hurried the bandaged Radeon back into the computer. Back to normal good performance.A bunch of us beta-testers had the discussion "way-back-when" about rates and OpenGL implementation. Rich Harvey contributed that FlyII relied heavily on front side bus speeds, and the Mac at that time had no faster than a 166 mHz FSB. Thus no one got great rates. This all leads me to think that a) Rich was right as always, and :( that X-Plane is much more dependent on VRAM than the processor for rates.I know this is a cross-sim subject, but I was sitting after work nursing a Henry Weinhart's (here's to you, Rich) and the results of tests over several years sort of coalesced to a conclusion. Maybe one of you young guys will do a sim some day and these observations may be of help.Regards,

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