Macintosh Display Cards Overview (3 of 3)

(This is a continuation of, "Macintosh Display Cards Overview (2 of 3)")
This article has been archived and is no longer updated by Apple.
- NuBus Block Transfer

One important display card acceleration feature is the NuBus block transfer
function. Macintosh Display Card 8/24 GC supports both master and slave NuBus
block transfer. Macintosh Display Card 4/8 and 8/24 support NuBus block
transfers in slave mode only.

Most Macintosh systems do not support NuBus block transfer so this function is
primarily a factor between NuBus cards with block transfer abilities. However,
the Macintosh IIfx does support block transfers in slave mode only.

NuBus block transfer facilitates faster movement of data. Normally data is
moved across NuBus in 32-bit words, 16-bit half-words, or bytes. Bus
availability must be arbitrated between each word transferred. Under NuBus
block transfer, the bus is arbitrated by the master, and then held while one
address word and 16 data words are transferred to the addressed NuBus slave.
Block transfer mode significantly accelerates the flow of data between the new
display cards.

Because the Macintosh and many other NuBus cards lack NuBus block transfer
support, another scheme is used to speed up data transfer between the Display
Card 8/24 and other NuBus clients. Pseudo-block transfer is similar to block
transfer in that it claims the bus for a 16 NuBus data word transaction;
however, it must send an address word for each data word that it sends. The
extra transfer activity makes pseudo-block transfer slower than block transfer
but still an improvement over normal NuBus access times.

- Multiple Display Cards in One System

When multiple display cards are installed, the Macintosh Display Card 8/24 GC
accelerates drawing in frame buffers of the Macintosh Display Card 4/8, 8/24,
or other frame buffer cards. Display Cards 4/8 and 8/24 show the most
improvement because they support slave NuBus block transfers and many other
display cards do not. Acceleration for frame buffers other than the one
resident on the Display Card 8/24 GC card would not be as dramatic because of
the greater amount of NuBus traffic required. Only one 8/24 GC may be used for
graphics acceleration in a system. If two cards are present, one will have its
acceleration function disabled.

- Upgrades

The Macintosh Display Card 4/8 can be upgraded to Display Card 8/24 by using
the Macintosh Display Card VRAM Kit.

The Macintosh Display Card 8/24 GC can be upgraded with the Macintosh Display
Card DRAM Expansion Kit, which improves the performance of applications that
use large off-screen bitmaps and other imaging methods.

System Software

System Software Version 6.0.5 or greater is required with Display Cards 4/8,
8/24 and 8/24 GC. Macintosh II, IIx ,and IIcx systems require the 32-bit
QuickDraw patch file. Macintosh IIci and IIfx systems have 32-bit QuickDraw in
ROM and require only System 6.0.5 or greater.

System Requirements

To use the Macintosh Display Card 4/8, 8/24, or 8/24 GC you need:
- A modular Macintosh II personal computer with an available NuBus slot
- System Software Version 6.0.5 or greater
- For Macintosh II, IIX and IIcx: the 32-bit QuickDraw software file is
needed to run 24-bit color applications.
- To take advantage of full 24-bit color, a minimum of 2MB of memory is

Support Issues

- Cables For Current Portrait and Two-Page Display Customers

Current Portrait and Two-Page display customers must purchase a DB-15 to DB-25
adaptor when connecting any of the new display cards. Customers buying new
Portrait and Two-Page displays will receive the proper cable.

- A/UX

The Display Card 8/24 GC will not initially work with A/UX. A/UX 2.0
compatibility is planned.

- Power Consumption

The Display Card 8/24 GC uses up to a maximum of 20 watts. In systems with all
NuBus slots utilized, the power requirements of all cards installed should be
added together to ensure that the NuBus power draw is not exceeded. Six-slot
Macintosh modulars provide 90 watts for nuBus, 3-slot Macintoshs provide 45

- Macintosh II ROMs

The original Mac II ROMs had several problems that will not allow the Display
Cards to function properly. There is a service program in place that will
replace the original ROMs with new ones.

Connector Pinouts

DB-15 Monitor Video Connector for Display Cards 4/8, 8/24 and 8/24 GC.

PinSignal Description
1 RED.GND Red Video Ground
2 RED.VID Red Video
3 CSYNC~ Composite Sync.
4 MON.ID1 Monitor ID, Bit 1
5 GRN.VID Green Video
6 GRN.GND Green Video Ground
7 MON.ID2 Monitor ID, Bit 2
8 nc (No Connection)
9 BLU.VID Blue Video
10 MON.ID3 Monitor ID, Bit 3
12 VSYNC~ Vertical Sync.
13 BLU.GND Blue Video Ground
15 HSYNC~ Horizontal Sync.
Shell CHASSIS.GND Chassis Ground

the Portrait and Two-Page Displays.

DB-15 Signal D-25
1 RED.GND A3 (Outer)
2 RED.VID A3 (Center)
3 CSYNC~ 5
4 MON.ID1 9
5 GRN.VID A2 (Center)
6 GRN.GND A2 (Outer)
7 MON.ID2 8
8 nc
9 BLU.VID A1 (Center)
10 MON.ID3 3
11 C&VSYNC.GND 4, 7,10
12 VSYNC~ 2
13 BLU.GND A1 (Outer)
15 HSYNC~ 6

Published Date: Feb 18, 2012