> Which are the actual effects of writing the dynamic memory refresh
register
> (LD R,A) on the MSX?
I think none. Maybe if you repeatidly set it to 0 very rapidly you might
delay the memory refresh but it's a wild guess.
> There were interesting copylock loading protections on the ZX Spectrum.
??? Oh ???
> Do you guys feature any kind of "nonstandard" CPU usage in your programs
> (such as undocumented mnemonics, self-modifying code, stack feedback...)?
Undocumented Mnemonics... Well I sometimes use the IXh, IYh, IXl and
IYl-instructions, but not very often. They are slow anyway, so most of the
time I just use other registers. IN F,(C) is nice, though.
I use self-modifying code quite often, especially useful for calls to the
Dos2 memoryroutines...
This is an example of how I code it (the $+1 is useful).
LD HL,#F3DF
LD (BDOS_C_SELF),HL ;self!
BDOS_C_SELF: EQU $+1
CALL #0000 ;self!
I use stack feedback if I need to skip the routine which called a sub by
POPing the return-adress into HL and then issueing a RET. Very useful for
disk-error handling routines.
Also, I like to use the I-register on the interrupt as a 'normal'
register... Most of the time it is useless, even slower, but it is still
'fun' to use it as an extra register. It can be used very well as a register
in which you keep a often-used value. Some sort of JIFFY, for example.
~Grauw
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