If you want a portable console that can play old Nintendo Entertainment System games, the easiest option is software emulation, whether you're using Nintendo's official Switch app, a portable PC, or some cheap knockoff emulator handheld. For those who want better accuracy than software emulation can provide, there's always the Analogue Pocket, which can (with current firmware) re-create the NES in hardware using its FPGA chip.
But some purists are unsatisfied with anything other than original hardware—that's the only possible explanation for projects like the TinyTendo, which goes to extraordinary lengths to squeeze an entire NES into a portable package roughly the size and weight of the old gray monochrome Game Boy. The project is the creation of hardware modder Redherring32, who eventually plans to open-source the project.
For miniaturization projects like this, you often see chopped-up or fully custom-printed circuit boards used with the original chips to contort the hardware into a new shape. This landscape orientation mod for the original Game Boy or the original Analogue NT are both good examples. But more drastic measures were needed to squeeze an entire NES into a handheld console, most notably the removal of bulky pins and ceramic that the original chips all use.
"TinyTendo utilizes real NES chips that have been physically cut and ground down smaller," wrote Redherring32. "A simple run down is that I sand away the bottom of the chip till I hit the die and leads, then I cut the chip smaller with a Dremel. The end result is 10x10x2mm, and surface mountable."
Soldering the hand-cut chips to a custom PCB creates a fully functional NES board that is "smaller than a Raspberry Pi 3," though the design also integrates a power management PCB, a button PCB, and other boards for audio and other functions. The console has a built-in LCD screen, charges over USB-C, and plays miniaturized (non-original) game cartridges, though full-size carts could be played with an adapter.
The downside of this project is that it requires the sacrifice of an actual NES to make it work. This prototype was made from an NES with a "very damaged motherboard," and we would encourage anyone who wants to make their own to harvest parts from non-functional consoles rather than destroying functioning hardware.
Redherring32 is responsible for several other modding and preservation projects, including open source PCB designs for the original front- and top-loading NES motherboards and the "PicoPad," a functional controller that's considerably smaller than the connector that plugs it into the NES.
Listing image by Redherring32/Twitter