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Review: Giga Designs 7455A G4 1GHz Cube CPU Upgrade
(2MB L3 SDR Cache)
By Mike
Tested: 12/5/2003
Installation Notes, Photos and Observations
Intro | Benchmarks  | Apps Tests | Game Tests | Installation | Specs/Design

Installation of any Cube CPU upgrade requires disassembling most of the core (removing graphics card, logic board, etc.) and I can't cover that here unfortunately. (Powerlogix has a Cube install guide PDF doc that may be of some help.) You can have OWC install your Cube upgrade however for a nominal fee. (Since fall 2001 when I installed the Duet Dual G4/500 in my Cube, I've taken Cubes apart more than 30 times at least, between swapping CPU modules in two Cubes, replacing problem modules, etc. but many Cube owners may prefer to have this done for them.)

Giga Designs CPU Upgrade Installed in Cube
Giga Designs

The GigaDesigns' Cube Upgrade page had a complete list of the CPU speed and voltage jumper settings. (Originally with earlier GD upgrades, I determined my own from the vreg chip, making a table of settings.) I used 1.35V setting at 1GHz and 1.45V at 1.2GHz but other samples may run well at different settings. (Keep in mind lower voltages run cooler. Voltage has a larger influence on heat/power use than frequency. Power usage is proportional to clock speed but also proportional to the -square- of the core voltage.) See the Specs page for photos of top/backside of the card, as well as other notes and info.

Temperature Monitoring

Maximum temperature seen during tests (after several hours of running Altivec Fractal Demo in automatic mode + playing music in iTunes with OpenGL visuals running) without the fan installed was 66.8°C which resulted in frequent system shutdowns (thermal overload). (66°C is well under the CPU chip's rating of 85°C, but still a very high core temp for the Cube.)
With the Gigadesigns 80mm Cube fan installed, max core temperatures were under 40C - a dramatic improvement. (Accuracy of the Fluke 80TK thermocouple module in this temp range is spec'd at 0.5% +/- 2°C.) Temperature in the Graphics card area of the core was also similar without a fan installed. In my opinion the fan is a must with any upgraded Cube for long-term internal component reliability including the expensive VRM board and the hard drive. (Even with the stock CPU, if you use your Cube for long hours I'd consider installing the $15 fan.)

I didn't have the thermocouple for use when I was running the original G4/450 CPU, although from past experience the core temperature also got very hot and the felt temperature of air wafting up from the core felt about the same as with this lower-voltage/higher frequency CPU upgrade installed with no fan. (However feel is not a good indicator for accurate comparison.) I also noticed in the past that the heatsink temperature on the OEM GF2MX was too hot to comfortably touch after hours of use. (I had heard years ago when the Cube was in production that the Cube's GF2MX model may have been slightly lower clocked than the tower model but I don't know if that's actually true. I'm using a card originally from a G4 tower.)

Note for ADC Display Users: Especially if you're running the CRT 17in (discontinued) ADC display - I'd not recommend using a CPU upgrade since the CRT (Tube) ADC display draws more than 50% of the 28V power from the AC adapter of the Cube. (The original max wattage specs on the 17in CRT ADC display that I remember was over 110W. The Cube's AC adapter which outputs 28VDC only is rated for 205W. Even with a large LCD ADC Display (70W max spec for the 23in/60W for the 20in) (Note: As I mentioned several years ago in the FAQ here - there are currently no DVI to ADC Adapters for the 17in CRT ADC display, since it uses Analog video signals and the DVI-ADC adapters only pass the digital DVI signals. There was originally an adapter for it by a 3rd party, but that adapter is no longer made.)
I had mentioned my concerns over the 17in CRT ADC display's wattage with an upgraded Cube to Tim at GigaDesigns last fall. Shortly after that conversation they wrote that my fears came true - they had a Cube w/17in CRT ADC display (with CPU/HD upgrades) fail, taking the VRM board and possibly graphics card with it. Just something to remember for ADC display users.

I've only used DVI or VGA displays on my upgraded Cubes, to reduce the load on the Cube's 28V supply. The Cinema ADC displays use less wattage (per Apple 70W Max for the 23in, 60W max for the 20in, and 40W max for the 17in current models) but if your Cube is heavily upgraded (i.e. a CPU upgrade, drive upgrade, GF3 graphics card, etc.) I'd suggest using a ADC->DVI adapter cable (about $39 list) and a DVI-to-ADC adapter (which has an external Power Supply) if you're using an ADC LCD display (esp. a large one), as it may extend the life of the Cube's VRM/Power Supply. The VRM board alone last I saw had a price of about $250 for instance.

System Compatibility:
The Cube Upgrade is compatible with any Cube model running firmware v4.1.9 (released in 2001).

OS Requirements:

  • OS 9.2.1 or OS 9.2.2
  • OS X (any version including Panther 10.3)

The next page has information on the upgrade's CPU and Cache. Or you may use the links below to jump to a specific page.

Giga Designs 1GHz Cube CPU Upgrade Review Pages

Intro | Benchmarks  | Apps Tests | Game Tests | Installation | Specs/Design

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