The rest of that difference can easily be explained by the difference in the class of hardware used. A desktop made today vs a laptop is roughly that factor 4. Not sure if back then there would have been laptops that you could have done this on for a more apples-to-apples comparison.
Modern laptops give great efficiency, when I went for solar power here the first thing to go was the desktop computer. I still have it, but it hasn't run in over a year and the elderly thinkpad that is now my daily driver uses far less power and still has enough compute to serve my modest needs. But if I would dive into something requiring much more compute I'd have to start the desktop again. Unfortunately power management is not such that computers can really throttle down to 'miser mode' when you don't need it, it's a good step but not as good as the jump between desktop and laptop.
also the 'memory wall', remember memory b/w did not grow at pace with moore's law. sure there are ways to mitigate it but that eat into chip budget and reflect when real world performance is calculated.
Yes, true and in a way that wall is still there. The way GPUs are limited in how much RAM they have because there is a way to sell you that memory at a multiple of the cost.
Imagine a GPU with a 128G or even 256G slot based memory section that is sold unpopulated. 8 SODIMM slots or so.
Modern laptops give great efficiency, when I went for solar power here the first thing to go was the desktop computer. I still have it, but it hasn't run in over a year and the elderly thinkpad that is now my daily driver uses far less power and still has enough compute to serve my modest needs. But if I would dive into something requiring much more compute I'd have to start the desktop again. Unfortunately power management is not such that computers can really throttle down to 'miser mode' when you don't need it, it's a good step but not as good as the jump between desktop and laptop.