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Accelerate Your Mac! - the source for performance news and reviews
The Source for Mac Performance News and Reviews
Review: Giga Designs 7455A G4 1GHz Cube CPU Upgrade
(2MB L3 SDR Cache)
Tested: 12/5/2003
Details of the Giga Designs Module
Intro | Benchmarks  | Apps Tests | Game Tests | Installation | Specs/Design

Giga Designs Cube G4/1GHz w/2MB SDR L3 Cache: (from sample provided)

  • CPU: Motorola MPC7455EC
    (1.0GHz rated 7455A low voltage model rated for +85C operation)
  • 64KB on-chip L1 cache
  • 256KB on-chip L2 cache
  • 2MB SDR L3 Cache
    (Samsung K7A803609B-QC25 x2, 250MHz rated)

The Giga Designs CPU upgrades are the only ones to date that have jumper settings to allow changing the CPU core voltage as well as the CPU speed (the bus multiplier that determines CPU speed). Giga Design's website has the CPU speed and voltage jumper settings info included on their Cube Upgrade page. (Gigadesigns site links removed after the company went out of business.)
Note: the settings order shown at GigaDesigns' page assumes you are looking at the board vertically oriented with the component side facing you and the large CPU speed jumpers on the left side of the board, as is shown in the photo on the installation page here. I first held the card with the component side up viewing it horizontally (edgewise) - which puts the jumpers in reverse location to what is listed on the Gigadesigns page.
As I mentioned previously on the installation page, I used 1.35V setting at 1GHz and 1.45V at 1.2GHz but other samples may run well at different settings.

As you can see from the photo of the bottom side of the board, the Cube upgrade is based on the same board as their new Dual G4 CPU upgrades (w/o the 2nd CPU and 2nd CPU L3 cache chips populated).

Giga Bottom side

Giga Top side

Temperature Monitoring

As mentioned in previous reviews here 7455 CPU based upgrades, the 7455A and 7455B CPUs have additional multiplier settings not available with earlier G4 CPUs. The 7455A/B has more bus/cpu ratio (multiplier) settings at the mid and high end (at the expense of lower ratio settings that were re-used for the upper ones due to a limited number of pins for that function). Some of the new ratios are re-used settings that were for previously used for much lower ratios on older CPU versions. Because of this, if set to one of these re-used settings, your Mac may not report the correct CPU speed. (Benchmarks like Xbench will also report the incorrect speed, although performance isn't affected by this since it's actually running at the correct speed.) The ratio settings (bus multipliers) that will not be correctly reported (as noted in the image above) are 8.5x, 9.5x, 10.5x, 11.5x, 12.5x and 13.5x. For this upgrade using the 10x (1GHz) and 12x (1.2GHz) settings this isn't an issue of course.

The Giga Design upgrades docs listed a 30 day Money Back Guarantee and a 3 year limited warranty as of the review date. And again, overclocking does not void the warranty I'm told, unless you boost the voltage. (30 day MBG subject to the returns policy of the dealer.) Complete details are in the included docs with the upgrade or their online warranty page.

For owner reports on CPU upgrades (any brand/mac model), search my Rate Your CPU Upgrade database.
I stress that owners of any upgrade should use it for several weeks at least before posting an entry in my database. If there are problems - double check the installation/settings and contact the vendor immediately if you need help. They often can provide a solution or identify the source of the problem.

Giga Designs 1GHz Cube CPU Upgrade Review Pages

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

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