Modchip-Function and construction-Printed
Function and construction
Modchips operate by replacing or overriding a system's protection hardware or software. They achieve this by either exploiting existing interfaces in an unintended or undocumented manner, or by actively manipulating the system's internal communication, sometimes to the point of re-routing it to substitute parts provided by the modchip.
Most modchips consist of one or more integrated circuits (microcontrollers, FPGAs, or CPLDs), often complemented with discrete parts, usually packaged on a small PCB to fit within the console system it is designed for. Although there are modchips that can be reprogrammed for different purposes, most modchips are designed to work within only one console system or even only one specific hardware version.
Modchips typically require some degree of technical acumen to install since they must be connected to a console's circuitry, most commonly by soldering wires to select traces or chip legs on a system's circuit board. Some modchips allow for installation by directly soldering the modchip's contacts to the console's circuit ("quicksolder"), by the precise positioning of electrical contacts ("solderless"), or, in rare cases, by plugging them into a system's internal or external connector.
Memory cards or cartridges that offer functions similar to modchips work on a completely different concept, namely by exploiting flaws in the system's handling of media. Such devices are not referred to as modchips, even if they are frequently traded under this umbrella term.
The diversity of hardware modchips operate on and varying methods they use mean that while modchips are often used for the same goal, they may work in vastly different ways, even if they are intended for use on the same console. Some of the first modchips for the Nintendo Wii known as drive chips, modify the behaviour and communication of the optical drive to bypass security. While on the Xbox 360, a common modchip took advantage of the fact short periods of instability in the CPU could be used to fairly reliably lead it to incorrectly compare security signatures. The precision required in this attack meant the modchip made use of a CPLD. Other modchips, such as the XenoGC and clones for the Nintendo GameCube, invoke a debug mode where security measures are reduced or absent, in this case a stock Atmel AVR microcontroller was used. A more recent innovation are optical disk drive emulators or ODDE, these replace the optical disk drive and allow data to come from another source bypassing the need to circumvent any security. These often make use of FPGAs to enable them to accurately emulate timing and performance characteristics of the optical drives.