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Review: Giga Designs G4/800 and 1GHz CPU Upgrades
By Mike
Published: 1/24/2003
Details of the Giga Designs Module
Intro | Benchmarks  | Apps Tests | Game Tests | Installation | Specs/Design

Giga Designs G4/800 no L3 Cache:(from sample provided)

  • CPU: Motorola 800MHz rated 7451 revison 2.1
    (P/N XPC7451 RX800PE - P = 65C, E = rev 2.1)
  • 256KB on-chip L2 cache (@cpu clock speed)
  • No L3 cache

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

  • CPU: Motorola 1GHz rated 7455 revison 2.1
  • 256KB on-chip L2 cache (@cpu clock speed)
  • 2MB DDR L3 Cache
    (Samsung K7D803671B-HC33 x2, BGA package)

It appears the copper heatsink (identical on both models) is a Celeron version. (Giga Designs notes that if you replace the heatsink - reuse the clip they provide as some may have too much tension and could damage the PowerPC CPU chip during installation.) Unknown RPM/CFM for the fan since the Gigadesigns label covers where that info would normally be shown, but it was quieter than my DP533's CPU heatsink fan that was removed during the upgrade.

These upgrades are compatible with the G4/AGP towers (Sawtooth thru Quicksilver models.)

CPU ID/revision checked using PPCChecker v2.6.1 by Michiro Isobe. (7451s will be reported as 7450 by PPCChecker since they have the same PVR ID. I verified the chip marking however on the 800MHz model, like most 800 AGP upgrades, it's a 7451 not the later/more expensive 7455.)

PPC Checker Info (1GHz model)
PPC Checker CPU ID 1GHz

PPC Checker Info (800MHz model)
PPC Checker CPU ID 800MHz
(7451 CPU actually, same ID as 7450)

Giga Top side

Giga Bottom side

The back side photo above shows one of the two DDR L3 cache chips present only on the 1GHz model (just to the left of the Vreg jumpers). It's a BGA package type; impossible to hand solder on for 800MHz model owners that wondered.

Bus Multiplier Jumper Settings Info (J1-J5):
The Giga Designs AGP upgrades are the only ones to date that have jumper settings to allow changing both the bus multiplier (determines CPU speed/allows for 100 or 133MHz bus use) as well as the CPU core voltage. (The Sonnet AGP upgrades autodetect the system bus speed, but are not manually adjustable, the Powerlogix upgrades are sold by 100MHz (Series 100) or 133MHz (Series 133) bus models and are not adjustable. Resistors set their ratio/voltage, which can be modified of course, but the jumpers on the Giga Designs models are much easier to deal with for those that want to experiment with higher speeds (at the risk of the warranty if voltages are boosted).
Although Giga Designs does not list the full range of possible ratio settings, they basically give you enough info to determine them from the 100/133MHz settings they provide, when you compare those jumper settings to the Moto CPU docs PLL info, you can easily create a matrix of other settings. For clarity I translated the specs doc table of 1/0 (TTL hi/lo) to one with open pins/Jumpers on. (Not all possible settings shown and of course there are some shown that are not going to work with the 800 and 1GHz CPUs.)

giga designs CPU speed setting

Note: The revison 3.3 7455 has a 8.5x and other multiplier settings not originally listed for the earlier rev 2.1 CPUs like the ones used on this upgrade. (This was noted in the Oct. 31st, 2002 news page here from a post by Michiro Isobe on the 3.x rev 7455's which also have a lower core voltage.) The 8.5 ratio would have been a welcome option for my 133MHz bus tower, since it would have allowed a CPU speed between 1.06GHz and 1.2GHz. (the former being a very small boost from rated speed, the latter being too high to reliably run, at least with the stock heatsink/fan combo.)

CPU Voltage Settings:
NOTE: My 1GHz sample was had multiple jumpers present (on J7,J9,J10) - the G4/800 sample had only a single Jumper (on J8) which threw me at first, since per the vreg specs doc, that would have been a 1.5V setting (below the recommended voltage for the 800MHz 7451). I emailed Tim at Giga Designs, who said to check the white label on the 800 module. For those with Serial Number prefixes of "0211A", there is only one jumper attached, but resistor pads R21 and R22 are present to pull down J9 and J10 (see bottom table for settings and red line in photo above shows R21/R22 location near Vreg chip).
Therfore for the "0211A" 800MHz model I had, the default core voltage was 1.65V (which for the 7451 docs I had was the recommended core voltage for the 7451 6xxMHz models, but the 7451 motorola doc I found listed 1.80 +/- 50mV for the 733-867MHz 7451. That's the closest doc I could find for the 7451 RX800PE model, but maybe there's others.) I assume the "0211A" models were done this to simplify manufacturing, since only one jumper (rather than 3) would be needed to be added for either the 800 or 1GHz model. (But the multi-jumper model is more flexible for future CPUs or overclocking without having to remove/cut resistors.)

Voltage Regulator Settings (J7-J10):
I searched the web and found the specs doc for the 2 phase voltage regulator chip on these modules Here's the PDF file link from distributor Arrow Electronics:
LTC1709 2-Phase, Adjustable, High Efficiency switching regulator (PDF doc, here's a google based HTML version.)
Page 14 of that specs doc lists all the options/voltage settings. To clarify things, I again created a table showing open pins and jumpers populated for each of the positions. (Specs Doc VID4 not used, it's only for >2.05V, which is not used for this design. VID3-VID0 in the specs doc corresponds to J7-J10 on the Giga board. As most of you know, 0 in the specs docs means low (jumper present), 1 means high (open/no jumper.) For clarity though I translated the specs doc table of 1/0 (TTL hi/lo) to one with open pins/Jumpers on.

giga designs voltage settings

The Giga Design upgrades docs listed a 30 day Money Back Guarantee and a 3 year limited warranty as of the review date (when run at the rated speeds). (Subject to the returns policy of the dealer.) See the included docs or their online warranty page for complete details.

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.

Index of Giga Designs G4 800/1GHz Upgrade Review Pages

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

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