Editing Apple Macintosh II Video Card (section)

=== Design ===
Apple's engineering document for the card, the ''NuBus Graphics Card Theory of Operations'' of August 1986, describes the design-verification version. The card is built around TFB, a frame buffer controller designed in Apple's Advanced Development Group, and supports 1, 2, 4 or 8 bits per pixel through a Brooktree Bt453 colour lookup table with 8-bit DACs for each of red, green and blue, giving a palette of 16 million colours. Two oscillators supply the pixel clock: 30.24 MHz for the Macintosh II monitors and 12.2727 MHz for RS-170 interlaced video. A 100 ns tapped delay line doubles the 10 MHz NuBus clock to the 20 MHz the TFB expects. The 512K version uses sixteen NEC µPD41264 video RAMs.<ref name="ngc">Toby Farrand, ''NuBus Graphics Card Theory of Operations'', Apple Computer, 12 August 1986: overview and features, p. 3; parts and cost list, pp. 3-4; NuBus interface, p. 8; video output, p. 9; debugging, pp. 9-10; final board features and layout, pp. 10-11; schematics, PAL equations, timing diagrams and the Bt453 data sheet follow. Hosted as [[:File:Apple NuBus Graphics Card Theory of Operations (1986).pdf]]; see [[Apple NuBus Graphics Card Theory of Operations (1986)]].</ref> The product description on the Higher Intellect wiki gives RS-343 video, composite sync and a power consumption of 10 W.<ref name="hi">Higher Intellect Vintage Wiki, [https://wiki.preterhuman.net/Macintosh_II_Video_Card_and_Expansion_Kit "Macintosh II Video Card and Expansion Kit"] (retrieved 2026-10-04). Secondary source: 640 × 480; RGB and monochrome; RS-343 video and RS-170 interlaced timing; composite sync, negative-going TTL; 10 W.</ref>

Two production cards photographed for Wikimedia Commons are marked FCC ID BCG9GRM0201 and 630-0153. One has a Toshiba-made TFB (344-0001, TC19G060AX) in a socket at U4B; the other a TFB marked L1A3009, 344-0001-1, with the Motorola logo. Both carry the Bt453KP, the 30.2400 MHz and 12.2727 MHz Saronix oscillators, NEC D41264C video RAMs in -15 and -12 speed grades, and a 2732 EPROM. Among the axial aluminium electrolytic capacitors, C13 is marked 220 µF 16 V and C22 and C23 10 µF 16 V.<ref name="photos">Akbkuku, [https://commons.wikimedia.org/wiki/File:Apple-macintosh-ii-video-card-v80019946.jpg "Apple-macintosh-ii-video-card-v80019946.jpg"] and [https://commons.wikimedia.org/wiki/File:Apple-macintosh-ii-video-card.jpg "Apple-macintosh-ii-video-card.jpg"], Wikimedia Commons, CC BY 4.0 (retrieved 2026-10-04). Part markings read from the full-resolution photographs.</ref>