Сообщение от
VELESOFT
Original BETADISK and all Czech BETADISC clones is designed for ZX48 or 128/+2(no +2A) only. BETADISK detect only bit D4 of port #7FFD = enable trdos if 48rom is set (D4=1). ZX48 use only 48 rom = work correct after switching to 48mode. On ZX128 and +2(grey model) work also without problem.
But connection to ZX 128+2A / +2B or +3 is very very dangerous and can destroy your ZX !!! This ZX models use 64kB rom paged on port 7FFD and 1FFD(also support true allram if D0 of port 1FFD is set). But BETADISC not detect value of port 1FFD. This problem can be fixed, if you enablle TRDOS only with 48rom (bit D4 of port 7FFD = 1, bit D2 of port 1FFD = 1 and D0 of port 1FFD = 0).
Next problem: +2A/+2B and +3 machines use different ZX bus pinout and use two singals ROMOE1 and ROMOE2. This bus also absent next signals as 9V etc.... If you connect original BETADISC to +2A, then ZX will destroyed - romcs signal from betadisc will on +2A ignored and trdos rom will collide with +2A rom of RAM memory of with ULA (if you set allram mode)
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