I don't know why I thought my older adapter from my T60 won't fit. It does. So I started to do my own measurements and discovered a very interesting thing:
Legend:
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W510/BAT = W510 running on battery
W510/90W = W510 running with T60 adapter 90W
W510/135W = W510 running with original 135W adapter
T60/BAT = T60 running on battery
T60/90W = T60 running with original 90W adapter
W510 = Core i7 820QM
T60 = Core 2 Duo 1.8
Both running Maximum Performance profile set to highest speed, WiFi 802.11n connected, bluetooth connected (mouse), medium brightness (n/a for T60 which is connected to running external panel)
SuperPI, 4M
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W510/BAT - 2:07, 2:07, 2:08
W510/90W - 1:13, 1:13 <--------- Single core, no problem even with Intel Turbo Boost
W510/135W - 1:12, 1:13
T60/BAT - 3:05, 3:05
T60/90W - 2:54, 3:03
HyperPI, 2M, 8 threads
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W510/BAT - 1:26 avg
W510/90W - 5:43 avg <------------- Horrible
W510/135W - 1:20 avg
HyperPI, 2M, 4 threads
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W510/BAT - 1:22, 1:22
W510/135W - 0:55 avg, 0:55 avg
W510/90W - 5:16 (:13-:12), 5:01, 1:38 (with disabled WLAN, BT, lowest brightness), 6:40 (with WLAN, BT, highest brightness) <-------- Horrible
HyperPI, 2M, 2 threads
W510/90W:
When more cores are utilised, Core Temp reported after a while Frequency 1196 MHz (133 x 9) only instead of 1861 MHz (133 x 14). It looks like during the PI calculation on 90W, it starts with 1.8 GHz, after few seconds it switches to 1.2 GHz. It keeps changing the frequencies, 10s - 15s on 1.8, 35s on 1.2. These times are variable, based on power consumption I think.
Summary:
For single core utilizing tasks, it does not matter (to be on the safe side, let's say most of the times). The charging may be slow, but that seems to be all.
For paralleled tasks, it is a completely different situation. The power of adapter matters a lot. The amount consumed by the system matters a lot. If you lower the consumption of other parts (turn off bluetooth, wifi, set lowest brightness), the speed penalty is smaller (still significant). With all bells and whistles - wifi, bluetooth, highest brightness, the speed penalty is huge.
For me it means to carry 135W allways with me, unless only office work is expected. Ok so always
