Thinkpad A21M: new power supply, it's roaring again

Many years ago I got an IBM Thinkpad A21M ("type 2628 DXG"), an early 2001 model (BIOS dates back to December 2000 and the undercover sticker shows a Windows 98 serial number). I upgraded disk and RAM and installed SuSE Linux 9.1; some time later the Thinkpad stopped working.

Soon after switching it on, after a short "clank" in the optical drive unit, it shut off. Generally this means some short-circuit problem on the battery side, but here it was also happening withouth battery and disks (floppy/hdd/cd), and it refused to turn on even with an (apparently) fully charged battery only. I eventually forgot the Thinkpad in the shed (ouch!), only salvaging its original 10 Gb disk and its 16V 4.5A power supply - the latter was a bit overkill for my Fujitsu Siemens Stylistic ST5022 but since then is doing its job. Thus I never had suspect on it... until today, when I found it again and -a moment before recycling- threw in a 100 watts (variable AC adapter, which 16V setting guarantees up to 5A) and it came back to life.

The actual culprit was not only the IBM power supply but the battery charging circuit as well: the first declares 4.5 amps at 16V (72 watts total) but actually gives less than 3.3 amps (that Thinkpad "type 2628" is actually rated 16V 3.36A, less than 54 watts): the Stylistic is happy with it, the Thinkpad no; the latter was only happy again with a 16V 5A capable supply (I guess that "5A" is a bit overestimated).

I am definitely sure because my killawatt shows:
- 10 to 21 watts while "poweroff" but charging the battery
- 53-54 watts while running the CPU-hungry screensaver

I was even able to recover its original 10 Gb disk, which since 2005 survived unimaginable stress and was never used till today: Windows XP SP1 completed its boot.

Quick specs:
- Pentium III @ 700 MHz, 192 Mb total RAM, 800x600 display
- 10 Gb IBM hard drive, 1.44" floppy disk drive, "24x" CD/ROM drive
- single USB 1.1 port, infrared, parallel, rs232
- two classic PCMCIA slots, ethernet, trackpoint, 16-bit soundcard

Now... enigma!

What kind of use will be good for a 192 Mb 700 MHz 10 Gb machine requiring more than 50 watts?

My last BeagleBoneBlack has 512 Mb 1000 MHz 64 Gb microSD and it only draws two watts...