Yes, MODE 1 for the main game MODE 4 for the service menu.

Mid-screen interrupt plus timed loop to effect the colour change to match the arcade game colours.

The MADSEL circuit is very interesting, delivers a great speed increase for pixels. Another interesting aspect is it uses no sprites, objects plotted using glyphs or line fills for the landscape. The satellite/smart bombs are plotted with leading edge pixels and pixels removing the trail.

Practical Wireless Tele-Tennis articles of '74 were reissued as a booklet a few months after. Picked up then, spent the next two years building it as a teenager. Etched my own hand-drawn PCBs with Ferric Chloride which is truly awful stuff. Was a messy contraption in a too small box but it worked.

Sound generation is definitely a black art on the Electron!

That combination could be about right. Didn't go down that route myself as it interferes too much with sound generation as I'm trying to output up to four channels at once. You might just get away with it though in Elite.

Missile Command on the Electron utilises the RTC interrupt and then burns off cycles to reach the city area for a palette change. Not entirely wasted as it uses some of this delay to synthesize three poly-counters, running in constant time, used in POKEY sound.

Some of you may remember him in the funny BT ad from the 80's playing General Custer.

youtu.be/zwaOP710lVY?...

It's a bit more than lift and shift you've got to know what you're doing and why.

I've found your code deep dives to be most informative and picked up a few ideas from them that I'd never get looking at by myself.

Looking forward to seeing more of this Elite project.

Electron R3R vertical scroll is in hardware, horizontal scroll in two self-modifying routines run in swr. Speed improvement makes the game quite playable. As many critical routines run here to squeeze the best out of it.

Using same in Missile Command running in MODE 1 that is even more restrictive.

Compared with the BBC and it's many swr boards to cater for it's a doddle. Just run through the available slots to test making sure that if it's less than slot 8 to de-select the basic ROM at slot 12 before selecting the swr.

It took a few days as it was in a friend's computer which didn't help. The board in question was from IFEL and the firmware has since been updated to remove this "feature".

Writing Atari Battlezone one recent BBC micro swr board gave me trouble : behaved exactly as it should except writes from within the swr address space to the swr address space failed. The swr test routine places code in the swr to test this behaviour and skip to the next bank to test if it failed.

Fun fact : when Superior Software announced they were re-issuing this the industry said why bother? Everyone who wants one has got one.

They then went and sold 20k+ units.

Fun fact : when Superior Software were testing this they had to borrow my 6502 second processor as they didn't have one themselves.

All the map packs from the original, AWIFS, Life of Repton and Repton Thru' Time are included together on the disc image.