The following frequencies are the dot clock rates of digital picture generators outputting 240p low-definition video signals that are compatible with NTSC monitors or otherwise at near-System M scan rates (15.7 kHz horizontal, 60 Hz vertical). The pixel aspect ratio that each rate produces, assuming ATSC's 704x480 pixel digital active picture area for a 4:3 picture at Rec. 601's 13.5 MHz sampling rate, is also given.
A few things may cause this ratio to differ in a particular environment:
Exact frequencies and PARs are given in lowest terms; frequencies of crystal oscillators and the dividers applied to them should be mentioned in a footnote or the description of a specific device.
| Frequency | Exact frequency | PAR | Exact PAR | Devices |
|---|---|---|---|---|
| 1.02 MHz | 315/308 MHz | 1.500 | 3:2 | Apple II (GR; each line repeated four times) |
| 3.58 MHz | 315/88 MHz | 1.714 | 12:7 | Devices with 1 pixel per NTSC subcarrier period: Atari 2600, Atari 7800, Intellivision |
| 5.00 MHz | 5/1 MHz | 1.227 | 27:22 | Atari Missile Command[1] and Crystal Castles hardware[2], Stern Berzerk/Frenzy hardware[3] (all 256px) |
| 5.37 MHz | 945/176 MHz | 1.143 | 8:7 | The 256px display of the TMS9918 (TI-99/4A, ColecoVision, MSX, and SG-1000), its descendants (MSX2, Master System, Genesis, Game Gear[4]), and other VDPs inspired by it (NES, TurboGrafx-16,[5] Super NES), and 256px mode of the original PlayStation[6] |
| 5.59 MHz | 16777216/3 Hz | 1.097 | 6328125:5767168 | Nintendo DS (256px) is the ~33.5 MHz (apparently 225 Hz) master clock divided by 6[7] |
| 6.00 MHz | 6/1 MHz | 1.023 | 45:44 | Data East Lock'n Chase/BurgerTime family (240 or 256px)[8], DECO Cassette System (256px)[9], and BreakThru family (240px)[10] Technos Double Dragon hardware,[11] SNK pre-Neo Geo 68000-based hardware,[12] Taito Arkanoid[13] and Bubble Bobble[14] hardware, Jaleco Mega System 1-A[15] (all 256px) Konami GX[16] and pre-GX (Mystic Warriors) family[17] (288px) Neo Geo MVS (320px)[18] |
| 6.04 MHz | 6048/1001 MHz | 1.016 | 65:64 | Neo Geo AES (320px)[19] |
| 6.05 MHz | 756/125 MHz | 1.015 | 625:616 | Namco NB-1/NB-2 family (288px)[20] |
| 6.09 MHz | 1071/176 MHz | 1.008 | 120:119 | Nintendo 64 (320px)[21][22][23] |
| 6.14 MHz | 135/22 MHz | 1.000 | 1:1 | ATSC defines the NTSC picture such that this is square on 4:3 monitors. The exact frequency is 6.13(63) MHz. |
| 6.14 MHz | 768/125 MHz | 0.999 | 5625:5632 | 48000 kHz (DAT and DVD audio rate) * 128[24] approximates square pixels to within 1 part in 800 Irem M52 (Moon Patrol) (240px)[25] Namco Pac-Man[26]/Galaxian[27] hardware and derivatives such as Pengo (288px)[28] Namco Super Pac-Man family,[29] System 86,[30] 1,[31] 2,[32] and ND-1[33] (all 288px) Konami GX400 arcade hardware (Gradius, Salamander, and a few others) (256px)[34] |
| 6.25 MHz | 25/4 MHz | 0.981 | 54:55 | Sega X-Board (320px)[35] |
| 6.29 MHz | 900/143 MHz | 0.975 | 39:40 | Sega Hang-On/Space Harrier[36], OutRun[37], and System 16B hardware[38] (all 320px) divide a VGA crystal by 4. Mode X (320x240) on VGA has twice the dot rate and repeats each line twice, giving it the same PAR. |
| 6.71 MHz | 4725/704 MHz | 0.914 | 32:35 | Sega Genesis and PlayStation 320px mode,[39][6] very close to SIF |
| 6.75 MHz | 27/4 MHz | 0.909 | 10:11 | MPEG-1 NTSC SIF (352 or 360px): CD-i, Video CD. Equal to Rec. 601 chroma rate or half Rec. 601 luma rate. Toaplan/Raizing 2nd-generation arcade boards (320px)[40] |
| 6.75 MHz | 27/4 MHz | 1.818 (i) | 20:11 (i) | Low-resolution DVD-Video, such as that produced by DVD recorders in long play mode |
| 7.00 MHz | 7/1 MHz | 0.877 | 135:154 | Toaplan/Taito Wardner hardware,[41] Toaplan "1st generation" hardware,[42] Technos Double Dragon 3 family (all 320px)[43] |
| 7.16 MHz | 315/44 MHz | 0.857 | 6:7 | Apple II (40-column text, HGR 280px); TG16 (mid-res, up to 352px); Atari 7800 (hi-res, 320px); Amiga, IBM CGA (40-column or 320px)[24] and EGA in 200-line mode (40-column or 320px)[44]; Atari 800[45]; Tandy Color Computer (COCO) and other computers using Motorola 6847 video chip[46]; Atari Tetris and Klax arcade games (336px)[47] |
| 7.67 MHz | 4725/616 MHz | 0.800 | 4:5 | PlayStation (384px)[6] |
| 8.00 MHz | 8/1 MHz | 0.767 | 135:176 | Williams 6809-based arcade system (276, 292, or 316px)[48] Capcom CP System and CP System II (384px)[49] |
| 8.19 MHz | 90/11 MHz | 0.750 | 3:4 | Commodore 64 and Apple IIGS 4bpp super hi-res[50] (both 320px). Square on widescreen monitors. |
| 8.60 MHz | 189/22 MHz | 0.714 | 5:7 | Capcom CP System III (384px mode)[51] |
| 10.74 MHz | 945/88 MHz | 0.571 | 4:7 | Twice the TMS9918 pixel rate produces 512px on Super NES, TG16, and PlayStation[6] and 496px on CP System III[51] |
| 12.27 MHz | 135/11 MHz | 1.000 (i) | 1:1 (i) | Square interlaced pixels |
| 13.42 MHz | 4725/352 MHz | 0.457 | 16:35 | PlayStation (640px)[6] |
| 13.50 MHz | 27/2 MHz | 0.909 (i) | 10:11 (i) | Rec. 601 luma rate as used in D1 tape and DVD Video (704px) Nintendo GameCube (640px), based on (nominally?) 27 and 54 MHz clock signals in digital AV out[52][53] |
| 14.32 MHz | 315/22 MHz | 0.429 | 3:7 | Apple II (80-column text, double hi-res); Amiga; IBM CGA (80-column)[24]; Tandy CoCo 3 (80-column) |
| 16.36 MHz | 1260/77 MHz | 0.375 | 3:8 | Apple IIGS 2bpp super hi-res (640px)[50] though Apple has claimed 5:12 instead[54] |
For comparison, here are some enhanced-definition (480p) rates, with a horizontal scan frequency close to 31.5 kHz:
| Frequency | Exact frequency | PAR | Exact PAR | Devices |
|---|---|---|---|---|
| 25.17 MHz | 3600/143 MHz | 0.975 | 39:40 | VGA mode 12h (640x480). The horizontal scan rate is twice NTSC, and the dot clock is 800 times that: 640 dots of picture and 160 of blanking.[55] |
| 27.00 MHz | 27/1 MHz | 0.909 | 10:11 | Twice Rec. 601 luma rate, as produced by progressive scan DVD players (704px) Nintendo GameCube[52][53] and Wii progressive component video (640px) |
DACRATE_NTSC by 8 to obtain the result here.
MASTER_CLOCK_25MHz is defined. System 16A contains the same crystal according to comments in xtal.h, but its use is not yet noted in segas16a.cpp.