Technical Specifications for the BeBox

ISA Bus

The ISA bus is provided for low-bandwidth I/O devices and for backwards compatibility with such devices as network adaptors and modems. Cards added to the ISA bus must have drivers compatible with the Be operating system.

ISA bus timing is generated by the Intel 82378 PCI-to-ISA bridge. The 82378 performs the following functions:

ISA Bus Bridge The 82378 converts PCI accesses to ISA accesses. Memory and I/O transactions are supported. The BeBox does not use any ISA memory locations; ISA I/O addresses have been allocated to the extra I/O features of the BeBox. A complete list of the usage of the I/O space is available in the I/O address map (forthcoming).

The BeBox register addresses have been chosen to avoid standard ISA cards such as modems and COM3 or COM4, LPT2 and 3, and FDD2.
ISA Interrupts All standard ISA interrupts are routed to the 8259 controllers, which are integrated into the 82378. PCI and SCSI interrupts may be routed to standard ISA interrupts. The 8259s may be bypassed by using the Be interrupt controller.
ISA DMA The 82378 provides 7 scatter gather ISA DMA channels. The channels are allocated as shown:

Channel 0 unused in BeBox
Channel 1 unused In BeBox
Channel 2 Floppy Disk Drive
Channel 3 Parallel Port
Channel 5 IDE
Channel 6 Audio Codec Capture
Channel 7 Audio Codec Playback

(Channel 4 is not available, it is used internally to cascade channels.)

NOTE: Development of hardware that makes use of the ISA DMA features for the BeBox is discouraged. Developers should look to PCI bus master cards for functions that would normally required DMA.
PCI Bus Arbitration The 82378 provides a mastership arbitration controller for the PCI Bus.
I/O Decoding The 82378 provides signals used to create I/O address decodes for the keyboard/mouse controller, real-time clock, IDE, and the front-panel LED bargraph option.

Technical Documenation for ISA Bus

The 82378 System I/O manuals in PDF format.

In order to assist with the porting of Linux to the BeBox, Be Inc made available (to Will Sowerbutt) some proprietry documentation about the BeBox ISA Bus. That information is now available here:

The documentation is marked "Be Inc. Confidential", and is hand annotated in parts. The document is titled "Be System ISA Bus", revision 0.4, dated 28/9/1994. Higher resolution copies of this documentation are available on request.

[Page 1], [Page 2], [Page 3], [Page 4]

ISA Bus Source Code

Below are some choice selections from the BeOS kernel that relate to the BeBox ISA Bus:

Questions? Comments? Contact Andrew Lampert (webmaster at bebox dot nu).