It seems that BLUEMSX tries to reproduce the fact that on msx1 out's to the VDP outside the VBLANK cannot be too close each other without loosing data.

I know also that when the screen is disabled (i.e. R1 has reset bit 6) the VDP is in a special mode where the I/O can be at the max speed.

I see instead the BLUEMSX does not emulate correctly this situation, where it contines to loose data even whe BLANK is zero.

This seems a bug in the emulator.
Is it ?

blueMSX as well as most other emus (BrMSX is an exception) does not emulate the slower I/O speed on MSX1. So its always possible to write as fast as possible to the VDP and VRAM regardless of VBLANK or if the screen is screen disabled.

At one point (one or two releases around 2.4 or so) blueMSX emulated the fact that if 4kB VRAM size (in R1 i believe) was selected and you disabled the screen, the VRAM slowly got corrupted. On MSX1 machines, the VRAM size bit needs to be set to 16kB if you want to disable the screen. There was however some bug related to this so I removed the feature. It was probably some other condition that was missing or so.

But as far as emulating the slow I/O I think only BrMSX does it.

if so, can u help me in this?
why this segment does not work

            ld      bc,0x0098
            otir
            otir
            otir

and this other works ?

            ld      bc,0x0800
1:          ld     a,(hl)
            out    (0x98),a
            inc    hl
            dec    bc
            ld  a,b
            or  c
            jp  nz,1b

ok, solved
thanks
(the bug was in my code )