Hello. I have mach3 and breakout board with parallel port (this is the cheapest version from ali).

All i have connected and works fine, but during system boot up, the board's outputs blinking.
Vacuum's and coolant's relays are connected to outputs and starting without reason 
Also when PC is turned off couple of outputs are enable.

Should i add some electronic between PC and board or outputs and relays?

I tried pull down signal with resistor 4k7ohm but it nothing changed.
In system registry ( HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Parport ) also i changed "Start" variable to 4.

Does anybody know how to resolve this? 

One of the old rules when Mach3 Parallel Port operation was the norm.

Mach3 should be up and running before your machine (and attachments) are switched on. Machine (and attachments) must be switched off before Mach3 is closed.

However, there is no reason why you cannot add additional electronics to act as an interlock and prevent unwanted operation of peripheral's.

Tweakie.

Hello. I have mach3 and breakout board with parallel port (this is the cheapest version from ali).

All i have connected and works fine, but during system boot up, the board's outputs blinking.
Vacuum's and coolant's relays are connected to outputs and starting without reason 
Also when PC is turned off couple of outputs are enable.

Should i add some electronic between PC and board or outputs and relays?

I tried pull down signal with resistor 4k7ohm but it nothing changed.
In system registry ( HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Parport ) also i changed "Start" variable to 4.

Does anybody know how to resolve this? 

I know this is question is old but my answer could help many others also

My Solution:
1. Make use of the enable feature in the BOB to enable the stepper-motor drivers.
(I use pin 14)
2. Disable the parallel driver in Windows 7 device manager (MACH3 does not need windows driver enabled)
3. Use the VFD Inverter output relay to only turn on coolant when Spindle is spinning.

Solved all the  "Parallel Port issues"
(this solution works 100% in Win7 but unfortunately does not work in Windows XP)