Question about Interface 2

[Haplo]

Hi,

I have a couple of questions about ZX Interface 2 (https://en.wikipedia.org/wiki/ZX_Interface_2). Sorry if it has been asked before; a quick search on the forum didn't yield anything.

Is Interface 2 supposed to work without a cartridge, or a cartridge is mandatory?
To my knowledge many people bought it to use the two joystick ports with cassette games, which means it should work without a cartridge.

So:
1. So should it work without a cartridge?
2. What should appear on the screen if you connect it without a cartridge to the Spectrum 48k unit and power the unit up?

Thanks for your help.

[PeterJ]

Hi [mention]Haplo[/mention]

You can find a copy of the manual at the link below which should answer your questions.

https://ia600604.us.archive.org/zipview ... anual.html

Peter

[Haplo]

Hi Peter,

Thanks for your reply. The problem is the manual says it can be used with cartridges, but it is not clear whether the cartridge is mandatory or it can be used without a cartridge.

So basically a simple question... should it work without a cartridge (to make use of its joystick ports with cassette games), or is a cartridge absolutely necessary for Interface 2 to work?

[redballoon]

It works without a cartridge. Nothing will appear on screen when it’s plugged in [without a cart] other than the usual (c) 1982 Sinclair Reasearch Ltd. or the initial screen from whatever Spectrum model you’re using.

[Haplo]

Thanks very much, that's what I needed to know. So Interface 2 should work without a cartridge, and powering up the unit with Interface 2 connected without a cartridge should show the usual "(c) 1982 Sinclair Reasearch Ltd." initial screen.

[AndyC]

Yup. Without a cartridge it should boot as normal and just act as a joystick interface. With a cartridge, it should start up in the game inserted since the cartridge ROM basically replaces the standard system ROM.

[FFoulkes]

https://en.wikipedia.org/wiki/ZX_Interface_2

"Only ten games were commercially released" (on cartridge). So fortunately it can be used with more than just these 10 games.

[Hedge1970]

https://en.wikipedia.org/wiki/ZX_Interface_2

"Only ten games were commercially released" (on cartridge). So fortunately it can be used with more than just these 10 games.

And if I am correct they where limited to 16k

Thankfully in the 21st century we have programmable cartridges

[PeterJ]

Yes, 16K.

There is a very interesting series of articles on the Fruitcake site:
http://www.fruitcake.plus.com/Sinclair/ ... uction.htm

[1024MAK]

And if I am correct they where limited to 16k

Not entirely true. In theory a program could be compressed, then uncompressed into RAM giving a game with more than 16k bytes of code.
Or a game could load extra levels from tape with the main game code in ROM.
Or bank switching could be used. However, due to the limited demand and the lack of suitable signals on the cartridge connector on the Interface 2 to make it easy, bank switching was only developed long after the Interface 2 went out of production.

Mark

[Joefish]

It's slightly different from 16K tape games though since nearly half of a 16K Spectrum's memory is taken up by the screen, so 16K tape games really only have 9¼K for code, data and variables, and the rest is the screen. A ROM game could have a full 16K of code and game data, use the RAM for variables (16K or 48K) and still have the screen.

And as MAK says, even a 16K cartridge could unpack compressed code or data into RAM before running it. That's how most cartridge consoles from the 16-bit days onwards work, since games were getting bigger far faster than ROMs were coming down in price. The N64 relies on this extensively, which is why you still get 'loading please wait' messages and limited 3D textures from a cartridge game.

Also note that the Interface II turns joystick inputs into keypresses, so won't work with +2A and +3 machines.