by Rick McLeod, Developer Technical Program
Silicon Graphics released the Audio/Serial Option (ASO) in early 1995, then released IMPACT Graphics for Indigo²(TM) in September 1995. With these two releases, we introduced some important new or modified hardware interfaces. The ASO works in Onyx/CHALLENGE® L and XL, whereas the IMPACT Graphics option is for Indigo². This article describes these interfaces so that you can deal with them more effectively.
The ASO is a mezzanine card for the IO4 that implements Indigo²-style audio capabilities and high-performance serial ports on the Onyx/CHALLENGE workstations. The ASO provides
The audio connections on this mezzanine card are part of a module that is mounted to the I/O panel. The module, which contains the same 3.5mm stereo jacks that the Indigo, Indigo², and Indy workstations use, has the following five connections:
The "Audio Interfaces" section of the Hardware Developer Handbook contains information on the connectors, pinout, and specifications.
The ASO also has 6 serial ports that are identified as tty[dmf]72 through tty[dmf]77. The 6 ports reside on 2 I/O panels--3 ports on each panel. The panels are located side by side on the I/O door. The interface is a female DB-9 connector. The interface can be either RS-232 or RS-422; the pinouts are shown in Table 1:
| Pin # | RS-232 Mode | RS-422 Mode | ||
| Signal Name | Description | Signal Name | Description | |
| 1 | - | No connection | TX_H | Transmit high |
| 2 | TX_L | Transmit low | TX_L | Transmit low |
| 3 | RX_L | Receive low | RX_L | Receive low |
| 4 | RTS | Request to send | RTS | Request to send |
| 5 | CTS | Clear to send | CTS | Clear to send |
| 6 | - | No connection | RX_H | Receive high |
| 7 | GND | Signal ground | GND | Signal ground |
| 8 | DCD | Data carrier detect | DCD | Data carrier detect |
| 9 | DTR | Data terminal ready | DTR | Data terminal ready |
When in the RS-232 mode the ASO serial port connectors are identical to the three RS-232 ports on the Onyx/CHALLENGE systems. However, the pinouts for the ASO serial ports in RS-422 mode are different from the pinout of the built-in RS-422 serial port found on the basic I/O panel on Onyx/CHALLENGE systems. As a result, cables made for the built-in RS-422 ports will not function properly with the ASO ports when in RS-422 mode. How the built-in RS-422 pinout compares with the ASO RS-422 pinout is shown in Table 2:
| ASO RS-422 Pin # | Built-in RS-422 Pin # | Description |
| 1 | 7 | Transmit high (TX_H) |
| 2 | 2 | Transmit low (TX_L) |
| 3 | 3 | Receive low (RX_L) |
| 4 | 9 | Request to send (RTS) |
| 5 | 5 | Clear to send (CTS) |
| 6 | 8 | Receive high (RX_H) |
| 7 | 6 | Signal ground |
| 8 | 4 | Data carrier detect (DCD) |
| 9 | 1 | Data terminal ready (DTR) |
With the information in Table 2, you can create an adapter that will make all RS-422 ports look the same.
Because IMPACT is a graphics subsystem upgrade, the hardware interfaces of these new Indigo² IMPACT systems are fundamentally the same as those of the previous Indigo² products using Extreme, XZ, and XL graphics subsystems. However, the hardware features that differ between the two systems include:
We will phase the power supply, prom, and backplane into production for all Indigo² systems over the next few months. Systems shipping with IMPACT graphics and Certain IMPACT systems will have the new backplane, power supply, and prom. These features are described in the sections that follow.
IMPACT graphics cards require a 3.3ávolt supply, so we designed a new power supply to support these cards. Because the graphics card requires new prom code to enable the IMPACT graphics, we created a new prom.
We changed the backplane by removing one of the EISA slots and adding a GIO connector. We made this change for two reasons:
GIO and EISA connectors do not have pins for 3.3ávolt connections, so we added a new connector to connect this voltage to the IMPACT boards. We removed one of the EISA connectors to make room for the additional circuitry and connectors.
We added one GIO connector, making a total of two for each logical GIO connection. This connector accommodates the architecture change of the IMPACT and IMPACT video cards, enabling the video cards to have direct GIO bus access.
These new backplanes will be phased into production to replace the original Indigo² backplane over the next few months.
In order to run IMPACT in an Indigo² chassis, you need the new backplane, power supply, and prom. With the independent phase-in of these three assemblies into production, you need to be sure that your system has all of them.
The part number for the prom is 007-1367-011; its checksum is BE92. The part number for the power supply is 060-8001-001. Check the backplane to ensure that it matches the one shown in Figure 1.
The change in the backplane for the IMPACT systems also affected the board outline for GIO64 cards as documented in Figure 4-34 of the GIO Bus Specification. The addition of the 3.3ávolt connector to the backplane has created the need for a "keep out" area on GIO64 boards intended for Indigo² systems.
The connector on the backplane comes close to the surface of any board placed in the slot. To avoid problems, keep components out of this area, and don't put traces on top of these boards.
We changed the stereo interface connector. Most people use this interface to connect stereo eyeglasses to our systems. On the Indigo² Extreme, XZ, and Indy, the old stereo interface connector was a 3-pin mini-DIN; the new stereo interface connector for the IMPACT graphics subsystem is a female DB-9.
In addition to carrying the stereo sync signal, the DB-9 connector carries two signals that are currently not implemented on the IMPACT (pins 3 and 5). Tableá3 lists the connector pinouts:
| Pin # | Signal Name | Description |
| 1 | Stereo_LEFT | Stereo left/right eye signal (1=left, 0=right) |
| 2 | SWAP_RDY_GND | Signal return ground |
| 3 | SWAP_READY | Reserved for future use |
| 4 | FRAME_LCK_GND | Signal return ground |
| 5 | FRAME_LOCK_N | Reserved for future use |
| 6 | DGND | Digital ground |
| 7 | DGND | Digital ground |
| 8 | STEREO_12V | +12V DC output to stereo-view device |
| 9 | - | Unused |
The next release of the Hardware Developer Handbook will include the information detailed here. Also, if you need an updated version of the GIO board outline (Figureá4-34 of the GIO Bus Specification), contact the Developer Program and we will send it to you.
We welcome feedback and comments at
devprogram@sgi.com.