Odd Kempston Interface 'Plus'

[Joefish]

Anyone any idea what's going on here (besides some phenomenally optimistic price gouging)..?

https://www.ebay.co.uk/itm/185888434153

[1024MAK]

Lego sponsored version?

Special Lemons version?

The phono socket is likely picking up the composite-ish video signal from the edge-connector.

Not sure if those yellow thinks are extra buttons, they do look like they may be.

Mark

[jpnz]

Not sure if those yellow thinks are extra buttons, they do look like they may be.
Mark

I'm curious as to what they may do - any thoughts?

I had fitted a button in an IF2 to force a reset, but stopped short at a second one for triggering an NMI given the logic in the stock ROM

[1024MAK]

As it’s on a joystick interface, my wild guess would be either duplicates of the joystick fire button and two direction buttons, or three extra fire buttons.

The Z80 always reads an eight bit byte. A Kempston joystick interface uses bits 0 to 5 for the four directions and fire. That leaves three inputs ‘spare’. Hence if this particular interface uses an eight gate tristate buffer chip, it’s possible to add three extra inputs…

Mark

[lfaria]

The Z80 always reads an eight bit byte. A Kempston joystick interface uses bits 0 to 5 for the four directions and fire. That leaves three inputs ‘spare’. Hence if this particular interface uses an eight gate tristate buffer chip, it’s possible to add three extra inputs…

Mark

And then add a "Spectrum Joystick Interface +" sticker over the embossed "Kempston Joystick Interface" area of a stock Kempston Joystick Interface (clearly visible, as the sticker used is slightly see-trough and the bottom side of the interface still has, visible on the 5th image, the stock "Kempston Joystick Interface" big sticker)

These 3 extra buttons would only be seen by specially crafted software, obviously.

As the seller doesn't say anything about these "plus" features, he/she's probably not aware that this isn't a stock Kempston item.

But using them as fire buttons looks extremely dangerous, as it will clearly "wobble" the interface and maybe cause all sorts of electrical problems and maybe even kill the speccy itself.

[Joefish]

The seller must have noticed I put a 'Watch' on it as I was just offered it for the bargain price of €89.99 !!! (plus shipping from Austria of €23.94).
I worry the lack of interest might leave him bluer than his schönen Donau.