Difference between Amiga and Atari 520?

[itix]

I have such a 520ST from 1984 (serial number 5000-odd I think) at home - except it's been upgraded to 1MB of RAM. How was the upgrade done? The only way was to solder new RAM chips on top of the old ones, taking the high address line via a wire connected somewhere else on the motherboard. No slot expansions here!

But for comparison, what kind of upgrades were made available to A1000 at that time? There was no Amiga 500 until 1987. At that time Atari had upgraded their machines to better specs (1040, STM and STFM). Gfx and sound options were not great but ST had higher resolution without flickery (with B/W monitor only).

Cant think of any other good points for ST :-)

[itix]

The copper co-processor makes it possible to use multithreading natively. No extra software needed. No cpu cycles spilled waiting.

Using copper is not multitasking. Modern GPUs are more complex than copper while using GPU still is not considered as multitasking.

[itix]

One can program a very quick scheduler when one can use already a wait commando (without making the cpu wait).

You can't because copper cannot control CPU.