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Just a nitpick - Spectrum was pretty open (at least if we are talking about 48/128). My father bought us Spectrum specifically because it was more open than alt
by js8 10y ago
Just a nitpick - Spectrum was pretty open (at least if we are talking about 48/128). My father bought us Spectrum specifically because it was more open than alternatives (Atari or Commodore), and he later bought the PC for the same reason (and I would never buy a Mac for the same reason).
Unlike its competitors, Spectrum had standard phone jack connectors for sound and magnetic tape recorder (so you could use any recorder). It also had a direct circuit board connection to the system bus on the back, and the schematics were available. My father built us the 8255 interface to have joystick and other peripherals connected.
- pjmlp 10y agoNot if we are talking about installing alternative OS into it.
- js8 10y agoActually, that was pretty doable too. Later, my father bought D40, which was a 5.25 inch disk unit produced by Czech company. The D40 had its own 16kB ROM which got mapped instead of the standard Spectrum ROM when NMI was invoked (the D40 ROM contained code to handle the disks). So it was totally possible for an external device to remap original ROM with something else, even RAM.
- vetinari 10y agoRegarding the RAM remapping: There was Didaktik Gama (made by the same company, that made D40), that had 80kB RAM. It was done by switching the 32768-65535 address range between two banks.
- vetinari 10y agoThere wasn't an OS to talk about. The 16kB ROM contained a BASIC interpreter, which was ignored by most applications you would load from the tape. If you wanted to talk to the hardware (joystick, printer), you did the I/O yourself.
- pjmlp 10y agoThe 16kB ROM BASIC interpreter was the OS! And you surely could not overwrite it.
- vetinari 10y agoNot from inside; but an external device could remap the address range (not that it was made often, except for D40/D80 which did that, replacing microdrive code with a floppy one) and the ZX128, which actually had two ROM banks. There weren't many useful things in the ROM, if you were writing your application. Maybe the font table and tape loader. On the other hand, if you were able to ignore the ROM, you got few bytes more of RAM, because you were able to repurpose the "system variables" area. The biggest "problem" with ROM that you were unable to replace it with RAM (until next reset, for example), thus taking precious 16kB out of 64kB address range.