- "Blow the CPUs out of the sky. I want total air supremecy" -Megabyte
The Central Police Unit defense forces serve as the combined military and police for a System. Their name is almost always abbreviated into CPU.
CPU personel almost always consist of binomes, in any system. No sprite has ever been seen serving in a CPU force, though at least one Numeral has been. CPU uniforms and vehicle designs vary from system to system.
The Mainframe force is led by the CPU General, a binome directly under Dot Matrix and Phong. Members of the CPU defense force wear green uniforms and gold helmets. Most of the air fleet is made up of flying armed police cars, as well as sleeker CPU Fighters. They also have a limited number of large CPU Tanks for use in battle. They command a large number of Anti-Aircraft Guns in defense of the Principal Office. Later, they were installed in almost every sector of the city.
In any crisis to hit Mainframe, the CPU force is usually the first on the scene and they provide back-up to the leaders of Mainframe. They have also been shown guarding important sites like the Archives.
They have been involved in multiple engagements with Megabyte and his ABC attack fleet. The two fleets teamed up during the Web World Wars, but immediately after the Web portal was closed, the ABC's attacked the exhausted CPU force and destroyed all but nine cars of the fleet.
During the Viral Wars the CPU's were confined behind the Principal Office shields, unable to protect Mainframe; missions were reduced to running diversions and recovery teams to ensure Enzo Matrix could reach Game Cubes and escape unmolested. After the Firewall was deployed, the CPUs used the time to rebuild their depleted forces. When Megabyte invaded the Principal Office following Silicon Tor's destruction, the CPU were forced to go underground and act as Dot's resistance troops, trading in their uniforms for heavy-set black body armor.
When Mainframe was restored by the User, many deleted CPU Binomes were restored and it was revealed several viral Binomes, now disinfected, used to serve in the CPU defense force, including Lieutenant Chauncy.
Following the System Restart, Giedi Prime was back under Mainframe control and the CPU force was able to add Armored Binome Carrier's to their army, repainting them in the CPU green-and-yellow. The increased CPU fleet battled the Guardian Armada when it attacked Mainframe at the beginning of the Net War and appeared to be holding their own for a while. However, they were hopelessly out numbered facing a fleet from the Super Computer. The Armada was expelled from Mainframe by Hexadecimal and a firewall was put up to seal Mainframe from the Net. The engagement led to moderate losses on the CPUs.
When Daemon successfully breached Mainframe's firewall, the CPU's arranged in a crossfire formation and were ordered to fire only on the Guardian Armada. Daemon came alone and the CPUs took no action, they were infected the instant she set foot on the System.
When Megabyte returned the CPU's used remote-operated craft to escort the fake Gateway Command to the Archives, drawing out Megabyte's troops. This small group of vehicles included CPU cars, fighters, ABCs and a single CPU tank retrofitted to carry the Gateway. The group was surprise attacked by Megabytes forces and easily destroyed. The viral ABCs locked a tractor beam on the CPU tank and towed it back to their base. Mainframe then used an originally-painted ABC to follow the virals back to base, where a CPU task force lead by Bob, Matrix and AndrAIa in taking down the enemy. They succeeded in overwhelming the surprised viral forces and managed to capture Megabyte himself. Unfortunately, they found out latter they had only captured an alias.
Desert Port System
The Desert Port System's CPU force cars were a large, stubbier size, blue coloring, and highly visible machine guns. the CPU officer uniforms resemble 19th Century French Foreign Legion.
The CPU force maintained a large desert prison, something unseen in Mainframe. Most likely this prison was built by the Guardians, entrusting the CPU's with its defense.
(Non-Canon) System 759.314.08.631
This system was briefly shown as one of many facing a viral onslaught; CPU forces battled the buffer-overrun Virus Psyton (a tentacled sea monster), even with the loss of their local Guardian, until the Gnosis weapon erased all virals. (Paradigms Lost)
These CPUs had uniforms resembling North American police officers, and peaked caps instead of helmets.
- CPU actually stands for Central Processing Unit, not Central Police Unit. Therefore, in reality, the antivirus would take the job of the (in universe) CPU.