2./I think there are delays : here is the program,

TempoL Equ 0
TempoH Equ 1

ORG 0000h

Start: Clr A
Leds: Mov P2,A
Mov B,#0
Mov TempoL,#0
Mov TempoH,#1
Time: Djnz B,Time
Djnz TempoL,Time
Djnz TempoH,Time
CPL A
Jmp Leds
end

3./i m using IspDos (from Wagner's site) and it "seems" to work fine...
how can i be sure?