G5 Powerbook power consumption analysis
It seems like there is a whole lot of misinformation going around about what is preventing G5s from being in the PBs now, so I thought I'd weigh in with my opinion.
I would assume that the primary factors in the design of the G5 Powerbooks would be:
- Same or at worst slightly higher power consumption.
- Higher clock speed than the current PBs, by at least 100 MHz across the range. (1.3->1.4, 1.5->1.6 GHz)
The battery life is a primary selling factor, and the higher clock speed is necessary for sales purposes. While the G5 has roughly the same performance as the G4 clock-for-clock, the subsystems are much improved, so I personally would buy the G5 over the G4 anyway.
Ace's Hardware posted a link to the power consumption of the new 970FXs, the new G5s (low power) in the Xserve. Power consumption at 2.0 GHz was 39W, at 1.2: 12W, and at 2.5: 55W. From this we can calculate that the G5s would use approx. 18W at 1.4 and 25W at 1.6 GHz. The current power consumption of the mobile G4s I believe is approx 15W for the 1.33 and 23W for the 1.5 GHz, from data from the Motorola's last G4 announcement. (This means that the G5s are NOT much hotter than G4s at comparable clock speeds, as some people are saying.)
We have a gain of 2-3W for this scenario, which is not too bad. If we jump 200 MHz instead, this increases to a gap of 5-7W, which is getting a little uncomfortable. However, once the 970FX production has increased, IBM can probably handpick processors which can run at a lower voltage (particularly at these lower clock speeds), which will probably lower the power consumption enough to go with the 200 MHz increase.
So, we can get the G5 processor into a Powerbook without affecting power consumption. The problem arises from the subsytems. In a desktop G5, we can have the processor consuming 50W without a problem, and the support logic (all the motherboard chips) probably use somewhere between 10-20W. However, if we just dumped this into the laptop, we'd have a processor+motherboard that used 30-40W. This is a problem.
The support logic needs to be redesigned for low power. A small part of this has probably already been done for the G5 Xserves, but there's probably more work there. One thing that would help, as others have mentioned, is moving the memory controller on die (ala Opteron/Athlon64). This would require a new CPU revision.
Beyond these considerations, I would presume that new Powerbooks would come with the full modern trappings of the G5. This would include SATA drives, of which the 2.5" variety are not yet widely available. No other notebooks have SATA drives.
It would be fair to say that we can expect Powerbook G5s in the normal timeframe, probably 8-10 months from now.
References:
Portable G4 power consumption:
http://arstechnica.com/news/posts/1077600172.html
Power Consumption of new G5 (970FX):
http://www.aceshardware.com/read_news.jsp?id=80000467
IBM document info:
http://www.aceshardware.com/forum?read=115063089
cant wait
