Apple Display Card 24AC
| Apple Macintosh Display Card 24AC | |
|---|---|
.jpg) |
|
| The 24AC in Apple's 1994 module identification manual | |
| Manufacturer | Apple Computer |
| Type | 24-bit accelerated NuBus display card |
| Interface | NuBus (7-inch card), DB-15 video connector |
| Compatible | Macintosh II family, Centris, Quadra and Power Macintosh computers with a NuBus slot; PowerBook Duo Dock |
| Dimensions | 6.5 × 4 in |
| Power | +5 V 1.8 A, −12 V 0.01 A (maximum) |
| Part number | 661-0432 (service module) |
The Apple Macintosh Display Card 24AC is a 7-inch NuBus display card with QuickDraw acceleration. It drives Apple's colour displays at 24 bits per pixel (16.7 million colours) and its grey-scale displays at 8 bits per pixel. It fits Macintosh II, Centris, Quadra and Power Macintosh computers with a NuBus slot.[1] Apple's service part for the card is module 661-0432.[2][3]
The 24AC is the same card, or very nearly the same, as Radius's PrecisionColor Pro 24AC.[4] Apple's own documents point the same way: the ROM label reads "Radius 24AC", and Apple directed owners of the Radius-sold version to Radius for support.[5]
Specifications
[edit | edit source]| Item | Specification |
|---|---|
| Interface | NuBus, 7-inch card |
| Video connector | 15-pin D-style (RS-343A) |
| Maximum depth | 24 bits per pixel (16.7 million colours) at every resolution |
| Size | 6.5 × 4 in |
| NuBus power (maximum) | +5 V 1.8 A; +12 V 0.0 A; −12 V 0.01 A |
| System software | System 7.1 or later |
| Memory | 2 MB of RAM or more (4 MB recommended) |
| Operating temperature | 10 to 55 °C |
| Humidity | 5 to 95 % non-condensing |
Figures from Apple's technical specification sheet.[6] Apple notes that some Macintosh II family computers can take the card only with an additional NuBus adapter card.[6]
Display modes
[edit | edit source]The 24AC supports five standard Macintosh resolutions and three more for multiple scan and VGA-type displays, all at up to 24 bits per pixel.[6]
| Macintosh resolutions | Additional resolutions |
|---|---|
| 640 × 480 at 67 Hz | 640 × 480 at 60 Hz |
| 832 × 624 at 75 Hz | 800 × 600 at 60 Hz |
| 1024 × 768 at 75 Hz | 1024 × 768 at 60 Hz |
| 1152 × 870 at 75 Hz | |
| 640 × 870 at 75 Hz (Portrait Display) |
The card reads the multiple scan sense codes and changes resolution without a restart, so a multiple scan display on a 24AC needs no sense adapter, even under older system software.[7] Apple qualified its AppleVision displays on the 24AC as well as on built-in video.[8]
Output by display
[edit | edit source]Apple's 1996 compatibility chart gives these maximum outputs for the 24AC.[2]
| Display | Output |
|---|---|
| Macintosh 12" Monochrome Display | 256 greys |
| Macintosh 12" RGB Display | 16.7 million colours |
| Apple Basic Color Monitor (14") | Not supported |
| Apple Color Plus 14" Display, Apple Performa Display, Apple Performa Plus Display | 16.7 million colours |
| AppleColor High-Resolution RGB, Macintosh Color Display, AudioVision 14, multiple scan and AppleVision displays at 640 × 480 | 16.7 million colours |
| Macintosh 16" Color Display and multiple scan displays at 832 × 624 | 16.7 million colours |
| Macintosh Portrait Display | 256 greys |
| Apple Two-Page Monochrome Monitor | 256 greys |
| Multiple Scan 17 and Multiple Scan 20 at 1024 × 768 | 16.7 million colours |
| Macintosh 21" Color Display and Multiple Scan 20 at 1152 × 870 | 16.7 million colours |
| AppleVision 1710 and 1710AV at 1280 × 1024 | Not supported |
Software and ROM versions
[edit | edit source]Acceleration needs the 24AC software installed. On a Power Macintosh, version 1.2 of the software or later is required; earlier versions run the card unaccelerated and report that the board cannot be used in accelerated mode.[9] The acceleration icons appear in the Options window of the Monitors control panel only when the "Apple Macintosh 24AC" file is in the Control Panels folder, a monitor is connected to the card, and that monitor is selected before Options is clicked; the window should be headed "Apple Macintosh 24AC".[10]
ROM version 1.0 does not work with System 7.5.3 or later: after an upgrade the screen becomes illegible when the resolution or colour depth is changed. Apple shipped its cards with ROM 1.1, which works with 7.5.3 and later. A ROM 1.0 card is either a DVT (developer) board or a card sold by Radius.[5] Low End Mac gives ROM 1.0 as working from System 7.1 to 7.5.2, and ROM 1.1 as working up to Mac OS 8.6.[4] To identify the version, read the label on the ROM, which names "Radius 24AC" with the version beneath. The solder side carries a bar code beginning "ACH".[5]
Compatibility notes
[edit | edit source]- The card works in the Centris 660AV, Quadra 660AV and Quadra 840AV, but Apple warns of significant speed problems in accelerated mode on those machines.[11]
- Apple lists the Duo Dock among the supported hosts.[1]
- Any Power Macintosh with a free NuBus slot can use the card.[10]
Video connector
[edit | edit source]The DB-15 pinout below is Apple's.[6]
| Pin | Signal | Pin | Signal |
|---|---|---|---|
| 1 | Red return | 9 | Blue video |
| 2 | Red video | 10 | ID 3 (sense) |
| 3 | Composite sync | 11 | Composite and vertical sync return |
| 4 | ID 1 (sense) | 12 | Vertical sync |
| 5 | Green video | 13 | Blue return |
| 6 | Green return | 14 | Horizontal sync return |
| 7 | ID 2 (sense) | 15 | Horizontal sync |
| 8 | Reserved | Shell | Shell ground |
Faults and servicing
[edit | edit source]Apple's service guides list the 24AC only as a whole exchange module, 661-0432.[2][3] Apple's general chart for video cards covers a dark screen, a bright screen with no picture and similar faults. Work through it in order, skipping the memory steps on a card without socketed RAM:[2]
- Reseat the card.
- Reseat any RAM or VRAM SIMMs on the card.
- Check the cable connections.
- Run the video diagnostic tests.
- Replace socketed VRAM or DRAM.
- Replace the card.
If the picture breaks up only after a system software upgrade to 7.5.3 or later, check the ROM version before suspecting the hardware.[5] If acceleration is missing on a Power Macintosh, check the software version and the control panel conditions above.[9][10]
Related pages
[edit | edit source]- Apple Display Card 4•8
- Apple Display Card 8•24
- Apple 8•24 GC Card
- Apple Macintosh Displays and Video Cards Service Guide (1996)
- Apple Service Module Identification Manual (1994)
References
[edit | edit source]- ↑ 1.0 1.1 Apple Computer, "Display Card 24AC: Description (6/95)", Tech Info Library article 13987, created 16 November 1993, revised 28 June 1995. In the archive.org collection Apple's Technical Information Library Articles, file TIL09433_to_TIL17062.pdf. Source for: 24-bit colour on Apple colour displays and 8-bit grey scale on grey-scale monitors; QuickDraw acceleration; compatibility with Quadra, Centris and Macintosh II family computers, Power Macintosh computers with a NuBus slot and the Duo Dock; 7-inch NuBus card; support for multiple scan displays, possibly through a third-party adapter.
- ↑ 2.0 2.1 2.2 2.3 Apple Computer, Macintosh Displays and Video Cards service guide, September 1996, hosted as File:Apple Macintosh Displays and Video Cards Service Guide (September 1996).pdf (described at Apple Macintosh Displays and Video Cards Service Guide (1996)). Video card parts list p. 325; troubleshooting chart p. 327; Table 16, "Video Cards–Card Compatibility and Video Output Chart", pp. 342-343.
- ↑ 3.0 3.1 Apple Computer, Module Identification, Apple Service part number 072-8124, June 1994, hosted as File:Apple Service Module Identification Manual (June 1994).pdf, p. 4.5.2 (PDF page 264), "Apple Macintosh Display Card 24AC 24-Bit NuBus Card", Apple P/N 661-0432, page dated January 1994.
- ↑ 4.0 4.1 Low End Mac, "Macintosh Display Card 24AC", https://lowendmac.com/1994/macintosh-display-card-24ac/ (retrieved 2026-10-04). Source for: the card being the same or nearly the same as the Radius PrecisionColor Pro 24AC; Mac OS support by ROM version.
- ↑ 5.0 5.1 5.2 5.3 Apple Computer, "Mac Display Card 24AC: ROM V1.0 Isn't Compat w/7.5.3 (10/96)", Tech Info Library article 20599 (TA36169), file TIL17065_to_TIL60496.pdf in the APPLE_TIL_ARTICLES collection. Source for: ROM 1.0 not compatible with System 7.5.3 or later; Apple shipped the card with ROM 1.1, which is; ROM 1.0 found only on DVT (developer) cards and cards bought from Radius; the ROM label reading "Radius 24AC" with the version below it; a bar code beginning "ACH" on the solder side.
- ↑ 6.0 6.1 6.2 6.3 Apple Computer, "Macintosh Display Card 24AC: Technical Specifications (12/94)", Tech Info Library article 14837, created 9 March 1994, revised 21 December 1994, file TIL09433_to_TIL17062.pdf in the APPLE_TIL_ARTICLES collection. Source for: system requirements (Macintosh II family with NuBus slot, Centris, Quadra or Power Macintosh; some Macintosh II family computers need an additional NuBus adapter card; 2 MB RAM, 4 MB recommended; System 7.1 or later); operating environment; 6.5 × 4 in; NuBus interface; RS-343A 15-pin connector; display modes; 24-bit maximum depth; NuBus power allowances; video port pinout.
- ↑ Apple Computer, "Macintosh Displays: Overview of Sense Codes and Adapters", Tech Info Library article 14890 (TA21607), file TA20315-TA29994.pdf in the APPLE_TIL_ARTICLES collection. Source for: sense code adapters for older cards; the 24AC as a programmable card that recognises multiple scan sense codes and changes resolution without restarting.
- ↑ Apple Computer, "AppleVision 1710AV: Frequently Asked Questions", Tech Info Library article 19108 (TA21682), file TA20315-TA29994.pdf in the APPLE_TIL_ARTICLES collection, question 7. Source for: AppleVision monitors qualified on built-in ports of 68040 and PowerPC Macs, the 24AC NuBus card and the ATI PCI card.
- ↑ 9.0 9.1 Apple Computer, "Macintosh Display Card 24AC: Compatibility With Power Macintosh", Tech Info Library article 15049 (TA31470), last changed 27 July 1994, file TIL09433_to_TIL17062.pdf in the APPLE_TIL_ARTICLES collection. Source for: full Power Macintosh compatibility from revision 1.2 of the 24AC software; earlier versions did not support accelerated operation on Power Macintosh.
- ↑ 10.0 10.1 10.2 Apple Computer, "Display Card 24AC: Power Macintosh Can Use Acceleration (2/95)", Tech Info Library article 17245 (TA33342), file TIL17065_to_TIL60496.pdf in the APPLE_TIL_ARTICLES collection. Source for: no problems using the card in any Power Macintosh with a free NuBus slot; the three conditions for the acceleration icons to appear.
- ↑ Apple Computer, "AV Series: Apple NuBus Video Card Compatibility", Tech Info Library article 14695 (TA31196), file TA30000-TA39999.pdf in the APPLE_TIL_ARTICLES collection. Source for: the 24AC is a 7-inch NuBus card and so fits the Centris 660AV, Quadra 660AV and Quadra 840AV; significant performance (speed) problems in accelerated mode.