>> Should I disable interrupts accessing the VDP register directly?
>
>Yes.
>
>Like this:
>LD A,value
>DI
>OUT (#99),a
>LD A,register+128
>EI
>OUT (#99),a
>
>Keep in mind that when executing an EI the interrupts will be enabled after
>the next instruction. So this is the way to keep the interrupts disabled as
>short as possible, which is always preferred (although not required).
Nice tip. This reminds me of the EI/RETI pair back in the ZX era. The fact
is that...
***I DON'T REMEMBER THE REASON!!!***
Is this tip used in MSX interrupts? Why (or why not)? ZX Spectrum used IM2.
>> Is it legal to call 256 times #FD9F with interrupts disabled at VDP level?
>
>Absolutely. But it might re-enable the interrupt. You'll have to check that.
OK.
>> Is it legal to tell Disk ROM to stop the motor with VDP interrupts
>disabled?
>
>Yes. Basically the DiskROM has nothing to do with the VDP. Just keep in mind
>that there is a chance that they enable the interrupts.
But not at VDP level I suppose.
>But why do you need to keep the interrupts disabled???
It was posted on this list that F700 had disk speed problems because of
poor disk interrupts. One way to cope with this was disabling interrupts
during disk loading. This way the F700 problem is solved at boot time
without disturbing other MSX models and without the hassle of saving/RET
poking/restoring the int vector.
Kiss you lot.
MARK 2
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