A comparison
FWIW, I've been thinking about the laptop issue for awhile, mulling things over (and perhaps subconciously waiting for a new 15" design
In any event, here's a cut-n-paste from an Excel spreadsheet that I've been working on. Unfortunately, I don't have the time this AM to go into all of the details, so I will probalby leave some people hanging. I expect that you can probably copy/paste this back into Excel to get nice columns to play with it yourself, etc.
Here goes...
Ave/Var XBench Score Processor Performance Index (P.I.) Description sample size Base $ Loaded $ Cost/P.I. Cost Delta Cost +% Value Index
Average: 83.8 PowerPC G4 @ 1.00 GHz 97% 15" TiBook $2,631 $2,701.06 $236 110% 108%
Std Dev: 7.8 PowerPC G4 @ 1.00 GHz 97% 382 $2,959 $3,037.79 $564 124% 96%
Average 75.9 PowerPC G4 @ 867 MHz 88% 15" TiBook $2,349 $2,661.89 -$46 98% 109%
Std Dev 5.2 PowerPC G4 @ 867 MHz 88% 342 $2,892 $3,277.22 $497 121% 89%
Average 86.1 PowerPC G4 @ 1.00 GHz 100% 17" AlBook $3,101 $3,101.00 $706 129% 94%
Std Dev 4.1 PowerPC G4 @ 1.00 GHz 100% 3 $3,335 $3,335.00 $940 139% 87%
Average 70.8 PowerPC G4 @ 867 MHz 82% 12" AlBook $1,880 $2,284.61 -$515 78% 127%
Std Dev 5.4 PowerPC G4 @ 867 MHz 82% 179 $2,395 $2,910.45 $0 100% 100%
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Okay, a quick rundown on formulas:
XBench Scores: the average & Standard deviation for each system, from the XBench website data.
Performance Index (PI): Simply the average from whichever system, divided by the score from the best system (17" AlBook). For example, the 12" AlBook = 82%.
Description/Sample Size: what the system is, and how many datapoints were available in XBench's database (Note: partial and invalid scores were deleted from the analysis). Be careful here, because the description text is much longer than the sample size value, and because of the lousy formatting here, the Dollar values that follow afterwords will look skewed.
Base $/Loaded $: My minimum buy-in cost, and how much I think I'd probably want to spend. All systems include a Superdrive within the base price. The loaded price adds more RAM, Max HD, and an Airport system. Prices are from Apple's website, under the Government Employee discount section (saves a bit more than hundred bucks or so).
Cost/P.I.: Above cost divided by the system's Performance Index. Because the 17" AlBook is the PI=1.00, these numbers are unchanged. The rest increase.
Cost Delta: The system's cost, divided by my "Loaded 12" price, expressed in dollars
Cost +%: As above, expressed as a percentage.
Value Index: the metric I'm having the most trouble with finding a good expression for. What I've listed here is:
V.I. =(System Performance Index)/(12"PI) * (System Price)/(Loaded 12")
There's a lot of holes in this, so I'm not sure if this helps or not, but it is kind of helping me mull over if I want to go with a loaded 12" or pick up a surplus 15". It kind of infers that I'd go for a 15" if the price was around $300 lower....
-hh