The addresses map to (see above links for prettier graph): HĮach scanline is stored linearily. There's 32*8=256 x 192 pixels on the screen. Memory below 0x8000 is 'slow' because the video hardware has priority to it fast(er) routines and data should It should be possible to use from 5b00 to ffff though (~41k).

So we have about 40k of usable RAM normally.

contended memory and contended io-port 254 make the above values largely useless.

different machines may vary by one clock.

one scanline: 128 clocks pixels, 24 clocks right border, 48 clocks retrace, 24 clocks left border.

after frame interrupt, 64 scanlines before first pixel.

i/o port 254 controls border color (bottom bits 0,1,2) and speaker (bit 4).

rom character set is at 0x3d00 - 0x3ff and contain 8 bytes per glyph, starting from ascii 32 (space).

In speccy emulator, be sure to set hardware->fast tape loader on unless you want to die prematurely of old age. a zx spectrum emulator, I like speccy.Note that I'm doing this on windows, but what I've got together here may be helpful for figuring these things out on other platforms too. It's (still) (well, probably forever) a work in progress, but Here's a bunch of stuff I've cobbled together to make a zx spectrum toolchain.

Speccy developers