This is my first time posting to this forum. I generally don't post to forums, but this topic is of interest to me for a few reasons. Below is some data I collected today. I hope you find it useful. I realize some of this data is in other threads, but there's no clear indication of whether or not that data is associated with a user that has a freezing, or non-freezing iMac with an ATI 4850 video chip. I also hope this allows you to make an informed purchasing decision. Configuration: iMac 3.06 GHz, 4 GB RAM, 1 TB HD, ATI Radeon 4850, Wired Numeric Keyboard, Mighty Mouse Date Ordered: 03/14/2009 Date Shipped: 04/17/2009 Date Received: 04/20/2009 Shipped from: Union City, CA Shipped to: Bay Area, CA Using Wi-Fi: Yes Bluetooth On: Yes Using Safari Public Beta 4.0: Yes Boot Camp: Yes (Win XP) Migration Assistant: No External Peripherals: No Uptime (as of this posting): ~10 hours [grep] | | | | | "ATY,EFICompileDate" = <"Mar 5 2009"> | | | | | "ATY,Copyright" = <"Copyright AMD Inc. All Rights Reserved.$ | | | | | "ATY,MemVendorID" = <0600> | | | | | "ATY,MemRevisionID" = <0200> | | | | | "ATY,RevID" = <a1440910> | | | | | "ATY,Card#" = <"109-B90901-00"> | | | | | "ATY,Rom#" = <"113-B9090C-181"> [Xbench] System Info Xbench Version 1.3 System Version 10.5.6 (9G3610) Physical RAM 4096 MB Model iMac9,1 Drive Type WDC WD1001FALS-40K1B0 Quartz Graphics Test 244.00 Line 236.63 15.75 Klines/sec [50% alpha] Rectangle 297.70 88.88 Krects/sec [50% alpha] Circle 232.05 18.92 Kcircles/sec [50% alpha] Bezier 232.08 5.85 Kbeziers/sec [50% alpha] Text 233.17 14.59 Kchars/sec OpenGL Graphics Test 238.33 Spinning Squares 238.33 302.33 frames/sec User Interface Test 447.44 Elements 447.44 2.05 Krefresh/sec [OpenGL Extensions Viewer] Test Status FPS 1.1 Passed 363 1.2 Passed 364 1.3 Passed 359 1.4 Passed 342 1.5 Passed 292 2.0 Passed 286 2.1 Passed 136 [OpenGL Driver Monitor] ATI Radeon HD 4850 OpenGL Engine Vendor Name ATI Technologies Inc. Version 2.0 ATI-1.5.42 GL Shading Language Version 1.20 Renderer Name ATI Radeon HD 4850 OpenGL Engine Display Mask 1 (0x00000001) Renderer ID 137735 (0x00021a07) Off Screen No Full Screen Yes Hardware Accelerated Yes Robust No Backing Store Yes MP Safe Yes Window Yes Multi Screen No Compliant Yes Buffer Modes 15 (0x0000000f) Color Buffer Modes 176194560 (0x0a808400) Accum Buffer Modes 8421376 (0x00808000) Depth Buffer Modes 7169 (0x00001c01) Stencil Buffer Modes 129 (0x00000081) Max Aux Buffers 2 (0x00000002) Max Sample Buffers 1 (0x00000001) Max Samples 8 (0x00000008) Sample Modes 3 (0x00000003) Alpha Sampling Yes GPU Vertex Processing Capable Yes GPU Fragment Processing Capable Yes Total Video Memory 536870912 (0x20000000) Total Texture Memory 525951488 (0x1f596200) I compiled and executed (Release Mode, i386 Target) the OpenGL examples included with Xcode. None of the examples froze my machine, regardless of settings (fullscreen, texture mapping, lighting and shading type, speed, etc). I tried to reproduce the freezing by watching various YouTube and Hulu videos in normal def and high def ('default' size and fullscreen). I tried this using Safari 3.x and 4.0. Couldn't reproduce the freeze as reported by others. Windows XP under Boot Camp also works fine, although I haven't done much testing with that yet. I used CPUTest to try and overheat my machine. The fans did kick in, but the machine never became unreasonably hot (I monitored the CPU, GPU and Heatsinks). Certainly not 'cool' by any means, but nothing unusual for an iMac. As a bonus, most of these tests were performed both before and after a clean install of OS X (complete software update both times). I still need to install Logic and Ableton Live to see if they cause any problems. I should have a few Valve games installed before the end of this week to test out. Judging by the current voting going on regarding those who have freezing machines and those who do not having freezing machines, it looks like you have a 50/50 chance either way. Which is pretty close to a coin toss. Which is pretty close to completely random luck. Which leads me to this conclusion: Apple probably had a batch of defective ATI chips. This probably caused the delay and they most likely fixed the problem later, but ended up with a warehouse of defective and non-defective machines co-mingled. However, it would be extremely cost and time-inefficient to sort, unbox, and test all the previously built machines. It's easier (and cheaper) for Apple to send out all the units, and have the consumers return the defective ones. That sorts the good from the bad, and eventually you're only left with a majority of non-defective machines (although there's certainly a chance you could get a defective machine twice). This is probably why Apple is so willing to exchange these machines while not publicly admitting there's a problem. For now, my iMac remains rock-solid. The benchmarks are impressive and it's a beast of a machine for an all-in-one. If I experience any freezes I'll report back. Thanks.