Spectrum +3 floating bus mod

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Lardo Boffin
Posts: 940
Joined: Sat Nov 26, 2016 2:42 am

Spectrum +3 floating bus mod

Post by Lardo Boffin » Fri Dec 21, 2018 1:59 am

I have applied the floating bus partial implementation mod from here https://spectrumforeveryone.com/technic ... trum-2a-3/ to a spare +3 I have at the moment and it seems to work fine.

As a quick aside does anyone know of any games that rely on this behaviour to work? It would be interesting to prove it actually does something.

I tested the +3 with a DIVMMCFuture and it worked fine. Once I got it working, anyway. My DIVMMC is VERY picky on +3s. I have tried it on three of them and all are the same - there is a sweet spot where it works and many where it is ignored.

I tried my Retroleum Smart card (which normally works fine although it only loads 48K games) and it didn’t work. I desoldered the resistor and it worked again.

Has anyone tried this and found any hardware no longer works?

Moving forward I was thinking about either -

A) Not bothering with it - I have plenty of Spectrums to load stuff that won’t work on this. Although I do quite like the +3 for some reason. The video quality is superb from it.

B) Extending one side of the wire to a switch and therefore be able to switch the mod on or off. I assume to do this safely the Spectrum would have to be switched off?

Any thoughts appreciated!
ZX80
ZX81 iss 1 (bugged ROM, kludge fix, normal, rebuilt)
Iss 3 ZXVid
TS 1000 iss 3, ZXPand AY, ZX8-CCB, ZX-KDLX & ChromaSCART
TS 1500
TS 2000
Spectrum 16k (iss 1 s/n 1499)
Various Spectrum 48ks plus a DIVMMC future and SPECTRA

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