... and AMIGA could run its
Workbench desktop on a 7 MHz CPU with 0.5 MB of RAM.
View attachment 24987
Amiga probably uses some hardware assistance to draw that UI. I am a PC guy so don't know much about Amiga internals, but in PC VGA one can set up modes that use less memory than minimal VGA amount (256kB), not only used for paging but for hardware assisted VRAM to VRAM transfer. The programmer can set up an offscreen buffer that way, use VRAM for 'assets' and draw them much faster (4x) than if CPU/RAM were used.
Amiga also, as far as I know, does graphics via DMA. I don't know whether it solely does that, but presuming Workbench uses that to redraw itself, it leaves the CPU alone so 7 MHz isn't really a factor. And there could be a blitter chip involvement too, for window composition?
I guess similar kind of GUI fidelity (but not looks!) might be achievable with 8 MHz 286 and some late ISA card with "Windows acceleration features" like ATi Mach64 in 1 MB RAM, where the 1 MB value would come from 286 protected mode requirement, and not minimal memory footprint.
The arrival of Amiga and Atari matched with the fall of DRAM prices which were limiting factor to computing evolution back then. Fast and affordable machines could not be made with late 70s/early 80s DRAM prices. Sometimes old PC software has very low memory requirements but it comes with a great speed tradeoff, like some adventure games that used VRAM as graphics buffer. They could run on 256kB PC, but the VRAM read operations are very slow.
It is a bit of a different beast to compare modern UIs against which are typically tripple buffered - window composition buffer, desktop comp. buffer, framebuffer.
Btw, I measured FreeBSD 5.5 on an MMX machine with XFree86/nVidia/WindowMaker. sendmail and that kind of stuff turned off, but networked. 24 MB idle desktop usage @ 640x480.
