Editing Atari 520ST (section)

== Display and Graphics ==
Video subsystem (Shifter + GLUE/MMU) characteristics:
* Modes: 320×200 4bpp (16 colors), 640×200 2bpp (4 colors), 640×400 1bpp mono. Color modes at 15.7 kHz H with 50 Hz PAL or 60 Hz NTSC V; mono at ~35.7 kHz H and ~71.5 Hz V.<ref>{{cite web |url=https://temlib.org/AtariForumWiki/index.php/Flat_Panel_Displays |title=Atari ST display modes and timings |publisher=AtariForumWiki |access-date=2025-08-13}}</ref>
* Palette: 9‑bit RGB (3:3:3), 512 total colors; up to 16 onscreen in low‑res, 4 in medium; mono is black/white only.<ref>{{cite web |url=https://en.wikipedia.org/wiki/Atari_ST |title=Atari ST |publisher=Wikipedia |date=2025-08-11 |access-date=2025-08-13}}</ref>
* Hardware features: No hardware sprites or blitter on the original 520ST; some later STF/FM boards accept an optional BLiTTER (PLCC‑68) upgrade footprint but it was not standard on 520ST.<ref>{{cite web |url=https://forums.atariage.com/topic/232054-520stfm-blitter-upgrade/ |title=520STf/m Blitter upgrade experiences |publisher=AtariAge Forums |date=2014-11 |access-date=2025-08-13}}</ref>
* Output levels and pins (DIN‑13): RGB pins 6/7/10; HSync 9, VSync 12; mono video 11; audio out 1; audio in 5; +12 V pull‑up on pin 8; ground 13; mono detect pin 4 (tie low for SM124 mode).<ref>{{cite web |url=https://www.oldcomputers.it/parts/atari/1040STF/docs/connettore_monitor_st.htm |title=ST monitor connector (pinout/levels) |publisher=oldcomputers.it |access-date=2025-08-13}}</ref><ref>{{cite web |url=https://old.pinouts.ru/Video/AtariStMonitor_pinout.shtml |title=Atari ST monitor pinout |publisher=pinouts.ru |access-date=2025-08-13}}</ref>