6 Solutions for the Mach3 Parallel Port Problem

Updated October 2026

Updated October 2026

If your old CNC computer has stopped working, or you want to use a laptop, you’ll probably find there’s nowhere to plug in the 25-pin cable from your CNC controller. Most modern computers don’t have a parallel port.

You can still use Mach3, but you need to choose the right hardware. An ordinary USB-to-printer cable won’t work, even if it has the correct plug on the end.

I ran my CNC foam cutter and OpenBuilds OX router from old Dell desktops for several years. They worked well, but as the computers started to fail, I moved towards microcontroller boards that I could use with a laptop. There are good reasons for taking either route, depending on what you already have and how much you want to change.

This article covers six options, from keeping an old parallel-port setup going to replacing the control software altogether.

Before you buy anything

There are three parts of the electronics that are easy to confuse:

• Motion controller: produces the accurately timed signals that tell the motors when to move. With an old Mach3 parallel-port setup, the computer does this work. An external USB or Ethernet motion controller takes over that job.
• Breakout board: provides connections for those signals, limit switches and other machine wiring. Some boards also include a motion controller, but a plain breakout board doesn’t.
• Stepper drivers: supply the current needed by the motors. A motion controller normally sends signals to these drivers rather than powering the motors itself.

You may have all three functions spread across separate boards, or some combined on one board. That matters when deciding what you can keep.

If your existing drivers and breakout board work well, you may only need an external motion controller. If you’re starting again, a controller with the breakout connections built in may be easier to wire.

Can Mach3 run on a modern computer?

The restriction is mainly with Mach3’s built-in parallel-port driver. That requires a desktop PC running a supported 32-bit version of Windows, up to Windows 7. It doesn’t work with 64-bit Windows or Windows 10 and 11.

Adding a parallel-port card to a Windows 11 computer doesn’t get around that restriction.

With a suitable external motion controller and its Mach3 plugin, you can use a newer computer, including a laptop. Check the controller manufacturer’s Windows requirements and installation instructions before buying. CNCdrive, for example, provides specific guidance for installing its UC100 drivers on Windows 10 and 11.

The plugin is the software that allows Mach3 to communicate with that particular controller. A board advertised as “USB CNC” isn’t automatically compatible with Mach3.

Useful links: Mach3 requirements and demo limits and UC100 information and downloads.

1 – Keep an old desktop PC with a parallel port

If you already have a working machine, this can still be the cheapest option.

I used several old Dell desktops donated by friends and family, running Windows XP 32-bit with 2GB of RAM. One was a Dell GX620, which had a small footprint and worked well in the workshop.

My foam cutter used a four-axis TB6560 controller with a DB25 parallel cable. I made several wings and fuselages with that setup, and also used a parallel-port PC with my OX router, using a different configuration.

Mach3 doesn’t need a powerful computer, but the PC needs to generate consistent step pulses. A faster processor on its own doesn’t guarantee a better machine controller.

For an existing setup, I’d keep the computer dedicated to CNC and leave it off the internet if it runs an unsupported version of Windows. Keep a backup of the Mach3 configuration, licence file, plugins and any custom screens or macros. Those become very useful when an old hard drive gives up.

The downside is the age of the equipment. My old PCs eventually started showing signs of failure, which was one reason for moving away from them.

If you’re building a new machine, I wouldn’t buy an old XP computer as my first choice. But there’s no need to replace a reliable working setup just because it uses a parallel port.

2 – Fit a parallel-port card to a desktop PC

Some desktop computers have a spare PCI or PCI Express slot that can take a parallel-port card.

This can be useful if the computer is otherwise suitable for Mach3’s parallel-port driver. You still need the supported 32-bit Windows installation described above.

Before ordering, check:

• The card fits the computer’s expansion slot and case.
• It supports the direct port access needed by Mach3, rather than only printing.
• Drivers are available for your version of Windows.
• Its signal levels meet the requirements of your breakout board.

Don’t assume that PCI means 5V signals or PCI Express means 3.3V signals. Check the actual card specifications and your breakout-board documentation.

You may also need to enter the card’s I/O address in Mach3. This is the address Windows assigns to the port; it isn’t necessarily the same as the original motherboard parallel port.

This option makes sense when you have a suitable desktop already. If you need to buy the computer as well, compare the total cost with an external motion controller before spending anything.

3 – Use a USB motion controller with your existing DB25 board

This is one way to keep your existing breakout board and motor drivers while changing the connection to the computer.

The important point is that you need a proper motion controller, not a generic USB-to-parallel printer adapter. The motion controller generates the step pulses; a printer adapter doesn’t provide the control Mach3 needs.

CNCdrive UC100

The UC100 USB motion controller fits into a small DB25-style housing and uses the standard parallel-port pinout. It connects to the computer by USB and to a suitable existing CNC breakout board through its DB25 connection.

CNCdrive currently lists support for Mach3, Mach4 and UCCNC. Each needs the appropriate software and plugin, so check the downloads for the package you intend to use.

Also check your existing board’s wiring and input requirements. The connector fitting doesn’t prove that everything is compatible.

CNCdrive warns about counterfeit UC100 devices sold through online marketplaces. I’d buy from the manufacturer or an authorised distributor so you know which hardware and software you’re getting.

What about the USB SmoothStepper?

The USB SmoothStepper was another way to connect Mach3 to parallel-port breakout boards. If you already have one working, the manufacturer still provides information and replacement units for existing installations.

However, Warp9 now recommends the Ethernet SmoothStepper for new builds. The USB version supports Mach3 only; it doesn’t provide a route to Mach4.

See Warp9’s USB and Ethernet SmoothStepper comparison.

Don’t assume that a USB connection electrically isolates the computer from the machine. That depends on the controller and any additional isolation hardware.

4 – Replace the controller with a USB board

You can also replace the existing controller rather than add a device to its parallel-port connection.

There are inexpensive USB boards advertised for Mach3, including NVCM-type controllers and boards sold with separate TB6600 drivers. Others combine the controller and motor drivers on one board.

The difficulty is that similar-looking boards can have different firmware, plugins and features. The TB6560 or TB6600 name describes the motor-driver chip or module; it doesn’t tell you whether the complete system works with Mach3 over USB.

Before buying, find the manual and the correct Mach3 plugin. Check how the board handles homing, limit switches, probing, spindle control and any other features you use. For a foam cutter, check that it supports four independently controlled axes moving together.

A low price is less attractive if you can’t obtain the software needed to make the board work. I’d favour a supplier who provides clear documentation and downloads for the exact model.

PoKeys57CNC

The PoKeys57CNC from PoLabs is a documented option with both USB and Ethernet connections. The manufacturer provides Mach3 and Mach4 plugins.

It connects to external motor drivers and includes connections for machine inputs and other equipment. It’s worth comparing if you’re replacing more of the electronics and want room for additional controls.

The manufacturer links above are more useful for choosing hardware than an old marketplace listing. Once you’ve chosen a model, check the current price, required accessories and delivery costs.

5 – Use an Ethernet motion controller

Ethernet controllers connect through a wired network port, using an RJ45 cable. They generate the motion signals in dedicated hardware, so you don’t need the old parallel-port driver.

There’s some network configuration to do, and you’ll need the correct power supply and breakout connections. Follow the manufacturer’s setup instructions, particularly for the IP address, firewall settings and cabling.

Ethernet SmoothStepper

The Ethernet SmoothStepper from Warp9 supports Mach3 and Mach4 and provides three parallel-port-style interfaces for connecting suitable breakout boards.

It needs an external 5V supply and separate motor drivers. Check which breakout board, cables and power supply are included when comparing prices.

Warp9 provides a PC setup guide and configuration utility to help with the Ethernet connection.

CNCdrive UC400ETH

The UC400ETH provides two parallel-port-style interfaces. It’s worth considering when you want to retain a suitable existing breakout board and change the connection to Ethernet.

The current manufacturer page lists Mach3, Mach4 and UCCNC support, with downloads for the relevant plugins.

CNCdrive UC300ETH

The UC300ETH-5LPT provides more inputs and outputs through five parallel-port-compatible headers. That may be useful for a machine with extra switches, a pendant or other equipment.

It also supports Mach3, Mach4 and UCCNC. You’ll need suitable breakout hardware and cables for the connections you want to use.

CNCdrive AXBB-E

The AXBB-E combines an Ethernet motion controller and breakout board.

This makes it a different proposition from adding a UC100 to an existing DB25 board. It’s worth a look when you’re rewiring the control box and want accessible terminals for the machine wiring.

CNCdrive currently lists Mach3, Mach4 and UCCNC compatibility. Check the installation information and supported features for your chosen software before ordering.

These are options to compare, rather than boards I’m claiming to have tested on my machines. Your choice will depend on the wiring you want to keep, the number of inputs and outputs you need and the software you intend to use.

6 – Change from Mach3 to another control system

If you already own a Mach3 licence and know the software, keeping it may save a lot of work. If you’re starting from scratch, it’s worth looking at the alternatives before choosing the hardware.

Mach4

Mach4 is the newer Mach control software, but it isn’t a straightforward upgrade installation over Mach3.

You need compatible hardware and a Mach4 plugin. Mach3 plugins don’t work in Mach4, and custom screens, macros and settings may need replacing or rewriting.

Several of the controllers above support both packages, but check the features implemented by the particular plugin. Support for the software doesn’t necessarily mean every machine function works in exactly the same way.

Try the demo with your actual machine hardware before buying a licence.

UCCNC

UCCNC is another option worth including if you’re considering CNCdrive hardware. It works with supported controllers including the UC100, UC400ETH, UC300ETH and AXBB-E.

That gives you another software choice when buying one of those controllers. It doesn’t mean UCCNC will work with any board advertised for Mach3.

UCCNC is paid software, and its licence is tied to the motion controller’s serial number. Check the supported functions against your machine and try it before committing to a change.

PlanetCNC

PlanetCNC supplies controllers that use its own control software. It belongs in this section because it replaces the Mach3 setup rather than providing an adapter for it.

If you’re comparing a complete replacement system, check the current controller range, software licensing and the features required by your machine. Don’t buy a PlanetCNC board expecting to install a Mach3 plugin and carry on with the same configuration.

LinuxCNC

LinuxCNC is free, open-source CNC control software. I used it on my machines and made some of my best projects with it. I had an IT background and some old computers available, which made it a practical choice at the time.

It does take some effort to learn and configure. LinuxCNC runs on Linux with a real-time kernel, which helps it carry out machine-control tasks at predictable intervals. The computer and interface still need to be suitable; the real-time kernel doesn’t remove the need to check latency and follow the hardware requirements.

You can use a suitable parallel port or supported interface hardware. For a modern Ethernet setup, the Mesa 7i96S is one example. It provides five step/direction channels, machine inputs and outputs, and spindle-related connections.

LinuxCNC doesn’t use ordinary USB motion controllers for real-time axis control. USB keyboards and some other non-real-time accessories are a different matter. Also, an Ethernet controller designed for Mach3 isn’t automatically suitable for LinuxCNC.

See the LinuxCNC system requirements and my article on using LinuxCNC with an OpenBuilds OX router.

GRBL, grblHAL and FluidNC

Microcontroller boards are the route I’ve moved towards for my own hobby machines. The board handles the motion, while software on the computer sends the G-code and provides the controls.

I built a USB foam cutter using an Arduino Mega and RAMPS board with NEMA17 motors. I’ve also used an MKS TinyBee running grblHAL on my OX router, with external motor drivers. You can read about converting my CNC router to USB here.

There are several firmware choices, but they don’t all run on the same boards:

• GRBL: the original Arduino Uno version is a three-axis controller. Mega-based versions and other forks add capabilities, but check the exact firmware rather than assuming every GRBL board supports four axes.
• grblHAL: runs on supported 32-bit microcontrollers. It offers more scope for additional axes and features, depending on the board and firmware build. It doesn’t run on the standard 8-bit Arduino Uno or Mega.
• FluidNC: runs on supported ESP32 hardware and includes a browser interface. Machine details are normally set in a configuration file, which can be convenient when changing a setup.

Project links: GRBL, grblHAL and FluidNC.

These replace Mach3 as the motion-control system. You choose a suitable sender or interface to go with the firmware. For grblHAL, ioSender is worth looking at; it’s the Windows sender I now prefer for my grblHAL controllers.

Small plug-in motor drivers have current and cooling limits, but that doesn’t limit every microcontroller system to NEMA17 motors. With suitable external drivers, you can use motors that need more current. Choose the driver to match the motor’s electrical requirements; NEMA17 and NEMA23 describe the mounting size.

A note for four-axis foam cutters

For foam cutting, don’t choose a controller just because it has four motor connections. One connection may be intended to copy another axis for a router’s second gantry motor.

You need four independently controlled axes that can move together. Also check:

• The axis letters used by the firmware, sender and generated G-code agree.
• G93 inverse-time feed is supported if your CAM output uses it.
• The sender handles the selected firmware and four-axis display correctly.
• There’s a suitable way to control the hot wire, or provision for a separate wire supply.

G93 controls how long a coordinated move takes. It’s useful when the root and tip profiles travel different distances, as happens with tapered or swept wings.

My Grbl HotWire article covers the software and supported setups in more detail. There’s also a separate guide to controller software for CNC foam cutters.

Which option makes sense for your machine?

What you have or want to do	Options to consider	Main thing to check
Keep a working parallel-port Mach3 machine	Existing desktop or a compatible parallel-port card	Supported 32-bit Windows, suitable hardware and backups
Keep a DB25 breakout board and use USB	Genuine UC100	Pinout, electrical compatibility and the correct plugin
Keep a breakout board and move to Ethernet	UC400ETH, UC300ETH or Ethernet SmoothStepper	Breakout connections, power supply and software support
Replace more of the control-box wiring	AXBB-E or PoKeys57CNC	Motor-driver connections, I/O requirements and supported features
Change software while using supported CNCdrive hardware	UCCNC	Controller compatibility and a separate software licence
Use LinuxCNC on modern hardware	Supported Mesa interface, such as the 7i96S	Real-time Linux setup and configuration effort
Build an affordable hobby router or foam cutter	Suitable GRBL, grblHAL or FluidNC system	Firmware, sender, motor drivers and machine-specific features

What would I choose now?

If your Mach3 machine works reliably and you only need to replace the computer, I’d first look at keeping the existing drivers and breakout board. A supported external motion controller may get you running again with fewer changes to the machine.

For a new hobby build, I’d look closely at a supported 32-bit microcontroller setup. That’s the direction I’ve taken with my own machines, and there’s plenty of choice in firmware and control software. For a foam cutter, I’d start with a documented four-axis setup rather than assemble a collection of boards and hope they work together.

LinuxCNC is still a capable free option if you’re prepared to spend time setting it up. Mach4 and UCCNC are worth comparing if you prefer a paid Windows control package.

Mach3 also needs a valid licence for normal use beyond its demo limits. The usual Mill demo limit is 500 lines of G-code; the Turn demo has a different limit. Check the official licensing details rather than assuming a copy bundled with a controller includes a valid licence.

Before buying anything, make a list of the parts you can keep and the functions your machine needs. That will usually narrow the choice much more quickly than comparing the number of axes printed on an advert.

Happy g-coding.