Once upon a time, CPU upgrade vendor PowerLogix offered a 1 GHz G3 CPU upgrade for the Pismo PowerBook based on the IBM PowerPC 750GX CPU, doubling the clock speed of the fastest stock Pismo – and with a full megabyte of Level 2 (L2) cache also running at 1 GHz.
The low-power IBM PowerPC 750GX is of the same CPU family as the 750FX chip that PowerLogix had previously used for Pismo upgrades, a CPU that had also powered the last generations of G3 iBooks running at several different clock speeds. However, the GX had twice the L2 cache of the FX and was available in faster clock speeds. (FX based 900 MHz upgrades were available from PowerLogix when this article was first published in 2004.)
The Fastest G3 Notebook Ever
The first product using the 750GX chip was BlueChip G3 Pismo running at 1.0 GHz, which was compatible with all Pismo PowerBooks – and 2.0 to 2.5 times as fast as the clock speed of a stock 400 MHz or 500 MHz Pismo. The L2 cache was also 5-6 times faster (the original cache runs at 40% of CPU speed), adding to the performance boost.
PowerLogix claimed that the BlueChip G3 Pismo with the 1.0 GHz 750GX ran “very cool” due to the lower power characteristics of this chip. This promise was not always borne out in practice, unfortunately, and the BlueChip upgrades developed a reputation for running hot, especially compared with 550 MHz G4 Pismo processor upgrades from competing vendors such as DayStar, FastMac, and Wegener Media. I’ve used Pismos running all three of those G4 upgrades extensively and can confirm that they do run very cool – probably cooler than the original PowerPC G3 750 400 MHz and 500 MHz chips that shipped in those machines.
However, the BlueChip upgrade’s CPU speed was adjustable on the fly to a lower clock speed for additional battery life and to help keep temperatures down. Tests performed by PowerLogix showed an additional 30 minutes on a full charge could be expected with the processor at reduced power (all other factors equal).
The BlueChip G3 1 GHz Pismo caught the interest of many Pismo users, but supply was limited initially due to IBM’s slow ramping up of 750GX production.
1 GHz G3 vs. 550 MHz G4
While I found the PowerLogix 1 GHz G3 upgrade intriguing, I opted to go with 550 MHz MAChSpeed G4 processor upgrades for my own Pismos, of which I’ve now owned three – two of which are still in regular production use. The one I’m typing this article on right now has a Wegener Media G4/550 MHz upgrade in it and runs so cool that I can’t detect any internal heat on the palm rests after half an hour’s uptime. It would be an understatement to say that I’ve been delighted with the results from all my Pismo 550 MHz G4 upgrades from three different vendors.
However, PowerLogix claimed that its tests (no longer available) showed that the BlueChip G3 Pismo 900 outperformed the G4/500 MHz Pismo upgrade they used to offer – even in applications that use AltiVec. That set of benchmarks was understandably somewhat selective.
For some objective context, check out MacSpeedZone’s benchmarks of a gaggle of Apple portables in Hands on Performance Report – G3/800 iBook to PowerBook G4/1 GHz.
The most closely relevant comparison there would be of the 900 MHz G3 iBook, which uses the same IBM 750FX chip as the PowerLogix 900 MHz Pismo upgrade, and the PowerBook G4 at 500 MHz and 550 MHz, which have a similar motherboard architecture to the Pismo.
In the AltiVec Fractal (Carbon) test, the 500 MHz G4 scored 24% as fast as the benchmark machine, which was a PowerMac G4 with dual 1 GHz processors, and the 550 MHz TiBook scored 31%, while the 900 MHz iBook G3 achieved only 8% – one-third to one-quarter of 500-550 MHz G4 performance.
On an iTunes MP3 Encode from CD test, the 500 MHz and 550 MHz G4 machines scored 53% and 44% respectively, with the 900 MHz iBook in the middle at 51%. (MacSpeedZone says, “Our assumption is that the CD drive performance is the bottleneck….”)
CPU Speed vs. Raw Power
I won’t dispute that a 900 MHz or 1 GHz G3 might well have blown the doors off a 500 MHz or 550 MHz G4 for many tasks in the Classic Mac OS era. Clock speed does count for something. But my overall impression based on running G3 iBooks and G4-upgraded Pismos is that the G4 will prevail in a lot of the AltiVec-intensive stuff. [Editor’s note: Keep in mind that Mac OS X is designed to take advantage of AltiVec. dk]
It really depends on what you use your computer for. I’m still a fan of the G3, and for my purposes I expect that I might have been able to wring more performance overall for the sort of stuff I do from the faster G3 upgrade than a slower G4, but a frequent Photoshop user would probably be better off with a G4 even at a slower clock speed.
That said, my 550 MHz G4 processor-upgraded Pismo was significantly faster than my 700 MHz G3 iBook even before I installed a 5400 RPM hard drive in the Pismo.
To posit an automotive analogy, the G3 sometimes feels more like a high-revving engine that is being lugged in too high a gear for the load it’s cumbered with, while the G4 is more like a torquey low-revving long-stroke V8 pulling the weight in a lower gear. I expect that the G4’s full megabyte of L2 cache versus the iBook G3’s 512 KB may have something to do with it as well.
PowerLogix also cited the advantage of “on the fly” CPU speed reduction to save battery life as increasing the G3 product’s attractiveness and noted that their PowerLogix BlueChip G3/900 had been outselling its G4 product by a margin of 4:1 before the latter was discontinued.
Price Comparison
The BlueChip G3 1 GHz Pismo sold for $399, so it was significantly more expensive than FastMac’s contemporaneous $239.95 G4/500 and $289.95 G4/550 solutions – and Daystar’s similarly clocked G4 Pismo upgrades at $289 and $329 respectively. PowerLogix’ 900 MHz G3 Pismo BlueChip upgrade sold for $349. The higher price did not help sales volume, and PowerLogix quietly discontinued the BlueChip Pismo CPU upgrades some time ago.
Something I found perhaps more interesting than comparisons of G3 vs. G4 performance was that the IBM 750 series chips appeared to have a bright future ahead of them, while it was basically the end of the road for Pismo pin-compatible Motorola G4/7410 chips at 550 MHz. Faster G4s (7455 and 7457) are physically larger chips that are not pin compatible, so they can’t be added to the Pismo CPU card by a chip swap. Until Apple sprang the G4 iBooks on us in the fall of 2003, I had been expecting the IBM 750GX to mark the next iBook speed bump, leading up to the release of the next 750 series chip release (HX?) in 2004 with an AltiVec-style vector engine.
I think that might have actually happened had it not been for the G3 iBook logic board defect debacle, which I suspect induced Apple to graft a modified 12″ G4 PowerBook logic board into the iBook as a ready-made fix.
Beyond 1 GHz
The IBM PowerPC 750GX microprocessor that was used in the PowerLogix 1 GHz BlueChip Pismo upgrade was architecturally based on the PowerPC 750FX processor, with which it was pin compatible although physically larger. Running at frequencies up to 1.1 GHz (PowerLogix uses the 1.1 GHz CPU in a $110 Power Mac G3 upgrade, but it never made its way into Pismo), the 750GX included 1 MB of internal 4-way set-associative L2 cache running at core frequency with cache locking, additional L1 and L2 cache buffers allowing pipelining of up to four data cache miss operations, and the capability for up to 200-MHz operation of the 60x system bus interface with additional bus pipelining. The 750GX achieved its high clock speeds, low power consumption, and small die size through IBM’s advanced 0.13-micron CMOS process, featuring copper and SOI technologies.
To reduce overall power consumption, the 750GX included low power modes and dynamic power management. Dual phase-locked loops (PLLs) allow processor clock frequency to be changed dynamically. A high-frequency mode can be used for compute-intensive operations, while a low-frequency mode can reduce power during idle times.
PowerLogix BlueChip Upgrades
- PowerPC 750FX 900 MHz with 512 KB of on-chip L2 cache running at 1:1
- PowerPC 750GX 1.0 GHz with 1 MB of on-chip L2 cache running at 1:1
As noted, these upgrades have been discontinued for several years now, and DayStar has also terminated its Pismo G4 upgrade product, although both FastMac and Wegener Media still offer 550 MHz G4 Pismo processor upgrades. It may still be possible to find PowerLogix 1 GHz and 900 MHz G3 Pismo upgrades used from time to time on eBay or elsewhere.
This article is an updated version of one that was originally published in the Road Warrior on MacOpinion on April 13, 2004.
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