Power Mac 4MB Video Card


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Note: MacGurus no longer carries the 512k VRAM SIMM required to upgrade this board.

The Power Macintosh 4MB Video Card is a PDS device which communicates along a 64-bit data path with the Motorola PowerPC 601 microprocessors in the Power Macintosh 8100-series. Compatible with the 80MHz, 100MHz, 110MHz and faster variants of the PPC 8100 and its clones, the 4MB Video Card has 2MB of soldered VRAM (visible on the schematic above, directly below the VRAM SIMM Connectors).

As Apple's intention was to ship the first generation PowerPC Macintosh with fast, 64-bit graphics subsystems, these cards represented a quantum improvement over previous Macintosh of the time, even those utilizing third-party video cards via the 16-bit Texas Instruments NuBus interface. Accelerating video I/O in this manner also enhanced performance system-wide, making the original Power Macs snappy machines indeed, even in comparison to blistering progenitors like the 40MHz Quadra 840av. The Power Mac 8100 in particular was designed as a graphics workhorse, with support for dual-displays and enough VRAM to yield millions of colors at resolutions up to 1152 x 870 on 21" displays.

Apple documentation is mute on whether the 4MB Video Card is compatible with the Power Mac 7100, but since the two computers share a common PDS bus, such cards should be interchangeable with the 2MB Video Cards which shipped in the PPC 7100.

Note: Apple service documention comments that 2MB and 4MB Video Cards can be distinguished by their part numbers (661-1748 & 661-1027, respectively) and by the color of their silkscreening. The 2MB card is silkscreened in yellow, and the 4MB card in white. The 2MB card additionally includes the numbers "128x8" in the lower lefthand corner of the card.

With four 68-pin SIMM slots, the 4MB Video Card accepts four (4) standard 512k 80ns VRAM SIMMs, which, in combination with the 2MB of VRAM soldered onto the card itself, yield the maximum VRAM configuration of 4MBs.

Specifications
Soldered Video Card VRAM		2MB.
Supported Modules		512k
Number SIMM Slots		Four (4).

The following monitors can achieve the stated resolutions in either 2MB or 4MB configurations.

Monitor		Resolution		2MB VRAM		4MB VRAM
12-inch Color		512 x 384		millions		millions
12-inch Monochrome		640 x 480		256		256
13-inch Color		640 x 480		millions		millions
14-inch Color		640 x 480		millions		millions
VGA		640 x 480		millions		millions
15-inch Portrait Monochrome		640 x 870		256		256
16-inch Color		832 x 624		millions		millions
19-inch Color		1024 x 768		thousands		millions
21-inch Color		1152 x 870		thousands		millions
SuperVGA		800 x 600		millions		millions
NTSC		640 x 480		millions		millions
NTSC flicker-free		640 x 480		256		256
NTSC		512 x 384		millions		millions
NTSC flicker-free		512 x 384		256		256
PAL		768 x 576		millions		millions
PAL flicker-free		768 x 576		256		256
PAL		640 x 480		millions		millions
PAL flicker-free		640 x 480		256		256

Note: Apple Technical Information Library (TIL) article Power Macintosh: VRAM Expansion Options (7/94) points out that "...VRAM expansion card(s) ...(do) NOT support resolutions below 8-bit (256 colors). In order to get 2, 4, or 16 colors, you must use the HDI-45 connector," which may be found on the rear of the logic board.

MacGurus appreciates the gracious technical corrections of Jeff Saxe to some of the data on this page.