Video output on all models is provided by the K1801VP1-037 VDC, a rather spartan chip. It is actually a standard 600-gate ULA with a VDC program that allows for two graphic video modes, high-res (512×256, monochrome) and low-res (256×256, 4 colors), and supported hardware vertical scrolling. Later models has 16 hardwired 4-color sets selectable from 64 color palette. It does not support text modes, but simulates two via BIOS routines: 32×25 and 64×25. Some operating systems such as ANDOS have managed to output text in 80×25 mode when displaying documents imported from IBM PC, by placing characters more densely. Output is through two separate 5-pin DIN connectors for a monochrome TV or color TV/monitor. Sound on all models is initially through a simple programmable counter connected to an onboard piezo speaker. Later, the General Instrument AY-3-8910 became a popular aftermarket addition.