Mac Musings

Is ATIcellerator Worth Trying?

Daniel Knight - 2004.09.03

"More Power!" Maybe it's a guy thing, whether we're dealing with power tools, cars, or computers. We like to tweak the hardware. We like to see how far we can push things.

I've been into personal computers since 1979 or so, and the first one I owned was a Commodore VIC-20. It had a cool expansion card that included a reset button and the ability to bank switch ROM cartridges, which meant you could copy them to tape - and video game piracy was born.

My first DOS PC, a Zenith, got tweaked as well. I replaced the 8088 with an NEC V20 chip, which was about 15% faster, and then used a freeware utility that let me reduce the number of times memory was refreshed per second for another 15% performance boost. The CGA video eventually gave way to EGA, and an EEMS card (remember those?) gave me extra memory beyond 640 KB.

My Mac Plus ended up with a faster than average hard drive and a Brainstorm upgrade, which made it run at 16 MHz. The Centris 610 never got a speed boost, although the hard drive, RAM, and VRAM were all upgraded at least once.

My first "tweaker system" was my first clone, a SuperMac J700. When I replaced the 180 MHz 604e CPU with a 250 MHz G3 card, I used a utility that let me tweak the backside cache from 1:1 to 3:2 for better performance. I also replaced the stock video card with a better one.

My TiBook had an immediate RAM upgrade from 128 MB to 512 MB, followed by a 5400 rpm hard drive a bit over a year later. My eMacs (700 MHz and 1.25 GHz) have booth had big RAM upgrades and used a 7200 rpm hard drive for better performance.

But where are the software tweaks? Apparently some iBooks can be overclocked in software, but I've heard of no such thing for my TiBook or eMacs. But now there's a piece of software that lets you overclock the GPU (graphics processing unit, video chipset) for better performance.

ATIcellerator II

The questions are does ATIcellerator II work, and if so, is it worth using. That's something I began to explore on my TiBook on Wednesday.

Step 1: Install the software, reboot the TiBook, and run Let 1000 Windows Bloom and Xbench 1.1.3 on the stock configuration. After recording the results, it was time to open System Preferences, choose ATIcellerator, and adjust the numbers.

ATIcellerator lets you adjust the memory speed and GPU speed separately. I started by bumping both speeds 5 MHz at a time from the 105 MHz default speed of the PB G4/400's video chipset. I saw immediate improvements in the Xbench scores, but much smaller ones with Let1kWindowsBloom.

I eventually reached the point where Memory was running too fast for the display and artifacts were appearing on the screen. With my setup, I found that 121.5 MHz was the fastest I could run video memory without seeing sparkles.

With both the GPU and VRAM at 121.5 MHz, I was measuring a 24.6% improvement on Xbench's Quartz benchmark, 22.9% in OpenGL, and 2.9% in User Interface. Let 1000 Windows Bloom was about 2.5% faster.

After an hour of tweaking and testing, I found that the GPU in my TiBook can run at 243 MHz - twice the fastest reliable memory speed, and the fastest I bothered to test. What I found was the the best results weren't always found at the same clock speed. After a lot of testing, I settled on 142.5 MHz for the GPU and 121.5 MHz for the memory as the best overall performance choice.

The eMac

My first eMac had Nvidia graphics, but the 1.25 GHz model has an ATI chipset, so I installed ATIcellerator on Thursday. Reboot. Open System Preferences, select ATIcellerator, and . . . oops.

Just launching ATIcellerator did weird things to the eMac's display. I couldn't read anything to change the settings, but I could click on the blue button to reset factory defaults. Then everything was okay again.

Reboot. Try it again. Same results.

ATIcellerator 1.0.2 just isn't compatible with the video in the 1.25 GHz eMac. Unfortunately, the installer doesn't include an uninstall option. Fortunately the presence of ATIcellerator doesn't mess up video - it's only when it's run that it messes up the screen. And fortunately it doesn't permanently change any PRAM settings, so in a worst case scenario, restarting the Mac will clear any changes made.


The ultimate question isn't whether ATIcellerator works, but whether it's worth using. Is a 5% performance boost in normal tasks worth adding a piece of software.

On the one hand, it can improve video performance, although whether that's going to be perceptible most of the time is questionable. Still, a bit better performance at no cost is worth trying. I'll continue to use it on my TiBook.

On the other hand, running the GPU faster may cause it to overheat and may also reduce battery life on 'Books. Setting too high a GPU clock frequency could possibly damage it. My advice: Take it easy to avoid the likelihood of damaging your hardware.

Your results may vary. User reports on Accelerate Your Mac vary from a minimal boost to around 15% - and at least one user duplicated my problems with the 1.25 GHz eMac.

If you have ATI Rage128 or Radeon video in your Mac and can spare 30 minutes to download and play with it, I suggest you give ATIcellerator a try. Other users report improved DVD playback, and 3D gaming performance should be improved as well. Just remember, you proceed at your own risk.