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I wrote loads of ZX Spectrum games in the 80’s for Firebird, Masterteonic and Software Projects. I had a Tatung Einstein hooked up to a spectrum via a custom RS232 cable. I had a program running on the Einstein that let me code in Z-80 assembler before porting it over to the spectrum to test. The port took about 10 seconds which allowed for rapid development....


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There was one Spectrum that had two 64K x 4 bit memory chips, but wasn't from Sinclair. It was the Inves Spectrum+, a clone manufactured in Spain. It had no contention, and the trick to achieve it was to make the ULA to do one read per clock cycle, and read the same data twice. Since the Z80 reads, at most, one byte per three clocks, this guarantees that the ...


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