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Review: Giga Designs 7455A G4 1GHz Cube CPU Upgrade
(2MB L3 SDR Cache)
By Mike
Posted: 1/30/2004
(Original tests run 12/5/2003)
= Links to Review Topics Pages =
Intro | Benchmarks  | Apps Tests | Game Tests | Installation | Specs/Design

Pros: Adjustable speeds (and CPU voltages) via jumpers (see specs page for notes and jumper settings). Ran 1.2GHz reliably in extensive stress tests with fan installed. (Higher speeds not tested.) No sleep/wake from sleep problems.

Cons: As with any Cube CPU upgrade, requires system disassembly to install.

Note: Due to the Cube's AC Adapter rating (28V/205W max), I'd not recommend using an Apple ADC CRT Display with any upgraded Cube due to the fact it draws over 100W (50%+) of the 28V Power Supply. I use DVI or VGA displays with my Cubes for this reason - even large Apple ADC LCD displays take a large portion of the Cube's 28V supply. Although it ran all apps tests without a fan, in extended stress tests Core temperatures exceeded 65°C and the Cube would shut down. With the fan installed, Core temperatures were MUCH lower, below 40°C in stress tests typically. The 7455A CPU chip in this upgrade is rated for 85C, but the issue is the Core temperature. Consider the fan (which isn't noisy at all) a must in my opinion. Even stock Cubes run very hot core temperatures w/o a fan. A low rpm fan will dramatically lower internal temperatures and extend the life of components including the hard drive and expensive VRM board.

Compatibility: Any Cube model, firmware 4.1.9 (released in 2001), OS 9.2.1 or later including OS X. 3yr warranty and 30 day MBG.

Test System: Refurbished G4/450 Cube with Geforce2MX (fanless), OEM 20GB drive, Airport card, 1GB RAM (2x512MB dimms). OS X 10.3.1. (Tests run before 10.3.2 update was released, but of course this upgrade is compatible w/10.3.2 also.)

Availability/Pricing: OWC was the USA dealer for Gigadesigns upgrades, but this Cube model is no longer in stock. OWC does currently list other Cube CPU upgrades however, but supplies are limited. (Several years after this review Gigadesigns went out of business.)


Due to initial problems with my (stock config.) refurbished Cube and then problems seen during extended stress tests without the $15 GigaDesigns Cube cooling fan (which was just received this week), this review is late. This model is Giga Designs first Cube CPU upgrade and unlike previous models, it's based on a lower voltage 7455A G4 CPU chip. Although the CPU is marked/rated for 1GHz, they basically guarantee it for 1.2GHz operation (and it shipped set to 1.2GHz). (For more info on speed settings, see the Specs/design page.)

See the linked pages of this review for Benchmark, Apps and Game performance comparisons as well as an installation page and specs page (w/jumper settings info).

As I noted above in the summary - I highly recommend a fan for any upgraded Cube. For this review I used a Fluke 80TK thermocouple module connected to my Fluke 87 meter to measure the core temperatures of the Cube running this upgrade at 1GHz and 1.2GHz - with and without the fan. The difference is dramatic. Although all the apps tests completed OK without the fan installed - during a stress test for several hours altivec fractal demo set to automatic mode + iTunes playing music with visuals on), the Cube's core temperature exceeded 65°C and frequently resulted in a shut down. After repeated tests like that I eventually had to replace the VRM board to get the Cube running again. At that point I refused to run any more extended tests without a fan. With the fan installed, core (and CPU) temperatures dropped dramatically - 20°C or more typically. The fan isn't noisy and als a blue LED for a cool (IMHO) glow effect under the Cube in dim lighting.

This review compares the performance of:

  • The original/stock G4/450MHz Cube (w/OEM Geforce2MX card)
  • The Cube with the 1GHz upgrade installed
  • The Cube with the 1GHz upgrade set to 1.2GHz

(Unlike most of my other full reviews, results from other upgrades/systems are not included.) With the fan installed, I'd almost bet 1.3GHz would be possible, but have not tested rates that high. For full details on the test Cube's hardware and software, see the system details listing below.

To see what others thought of their CPU upgrades - you can search the Rate Your CPU upgrade database here for reader reports on most every CPU upgrade by brand and/or mac model. For previous full reviews of G4 and G3 CPU upgrades, see the G4 reviews and G3 reviews pages.) OWC's product pages also link to their comparison tests of AGP CPU upgrades.

Review Table of Contents:

  1. Applications Performance: Tests with QT to MPEG4 conversion, iMovie3 quicktime movie export, iTunes4 MP3 encoding, Photoshop 7.0 (50MB image/21 filter tests), and Preview PDF document scrolling speed.

  2. Games Performance: Tests with Unreal Tournament 2003, Unreal Tournament X, Jedi Knight II, and Quake3.

  3. Benchmark Performance: Altivec Fractal (FPU test), CineBench 2003 and Xbench test results.

  4. Installation: Comments on installing the upgrade, photos of it etc.

  5. Specs/Design: Details of the upgrade's CPU and Cache, jumper settings, etc..

System Compatibility:
This CPU upgrade is compatible with all G4 Cube models (natch) with Cube Firmware v4.1.9. (Cube Firmware update released in 2001.)

    OS Requirements:
  • OS 9.2.1 or OS 9.2.2
  • OS X (any version including Panther/10.3.x)

Other Owner Experiences: For owner ratings of most every CPU upgrade for any upgradeable Mac, search the Rate Your CPU Upgrade database.

Test System Details:

  • Apple G4 Cube 450MHz (7400 G4 w/1MB L2)
  • 100MHz (SDR) bus w/1GB RAM (2x512MB dimms)
  • OEM Nvidia Geforce2MX 32MB VRAM (fanless)
  • OEM Seagate 20GB (20% free space) Hard Drive w/OS 9.2.2 and 10.3.1 installed
  • Onboard ATA/66 hard drive controller
  • OEM DVD-ROM drive
  • Airport active for all tests

Display used was a IBM 15" LCD (VGA connection). The hard drive was not optimized. For MP3/CD rip tests, a Lite-on 40125S (40x12x48x) CDRW in a Pyro Firewire case was used.

You can follow my preferred path through the review by continuing to the next page, or 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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