Compaq AlphaStation XP1000 System PCI and ISA Configuration

PCI and ISA Configuration

Topics covered in this section include:

PCI Restrictions
PCI IDSEL Allocation
Primary Bus 0 PCI IDSEL Assignments
Primary Bus 1 PCI IDSEL Assignments
Secondary Bus PCI IDSEL Assignments
ISA Bus

PCI Restrictions

The following restrictions apply to PCI options.

64-Bit cards can not be used in Slot 2.
Not all graphic cards supported will work in option slots 4 and 5.
- All TGA-2 and Powerstorm 4D51T options must be installed in PCI Bus 0 (Slots 1,2,3).
- In a multi-head environment with ELSA Gloria modules, the VGA-enabled ELSA Gloria must be installed in PCI Bus 0 (Slot 1,2,or 3).

To locate a specific PCI bus and option slot, see the Block Diagram and Option Slots.

IDSEL is used to determine the PCI device that is being addressed for a configuration cycle. The Compaq AlphaStation XP1000 System uses a PCI AD bit during the address portion of the configuration transaction to assert the IDSEL input to a given PCI Device. Each PCI device on a given PCI bus (PCI-0 or PCI1) has a unique PCI AD bit for IDSEL. The following table shows how the devices are allocated their IDSEL.

PCI Device	IDSEL	PCI Bus #
Cypress 693UB	PCI AD[18]	PCI Bus 0
PCI Slot 1	PCI AD[22]	PCI Bus 0
PCI Slot 2	PCI AD[23]	PCI Bus 0
PCI Slot 3	PCI AD[24]	PCI Bus 0
Ethernet 21143	PCI AD[14]	PCI Bus 1
SCSI 1040C	PCI AD[17]	PCI Bus 1
P2P Bridge	PCI AD[19]	PCI Bus 1
PCI Slot 4	PCI AD[25]	PCI Bus 1 Secondary
PCI Slot 5	PCI AD[26]	PCI Bus 1 Secondary

To read a PCI configuration register, you need to know which bus (primary or secondary) the device is on, and which PCI AD line is tied to its IDSEL pin. The tables which follow depict the Compaq AlphaStation XP1000 with PCI dense configuration space.

PCI Bus 0 Primary IDSEL Assignments

IDSEL Bit	PCI Base Address	CPU Base Address	MLB Device
AD<18>	0004.0000	801.FE00.3800	Cypress 693UB
AD<22>	0040.0000	801.FE00.5800	Slot 1
AD<23>	0080.0000	801.FE00.6000	Slot 2
AD<24>	0100.0000	801.FE00.6800	Slot 3

PCI Bus 1 Primary IDSEL Assignments

IDSEL Bit	PCI Base Address	CPU Base Address	MLB Device
AD<14>	0000.4000	803.FE00.1800	PCI-Ethernet
AD<17>	0002.0000	803.FE00.3000	SCSI 1040C
AD<19>	0008.0000	803.FE00.4000	P2P Bridge

PCI Bus Secondary IDSEL Assignments

IDSEL Bit	Secondary PCI Base Address	Primary PCI Base Address	CPU Base Address	MLB Device
AD<25>	0200.0000	0002.4801	803.FE02.4800	Slot 4
AD<26>	0400.0000	0002.5001	803.FE02.5000	Slot 5

Note: The P2P Bridge must be programmed before accessing the Slot 4 and Slot 5 configuration registers. SRM sets up the bridge automatically, so the registers can be accessed directly. The SROM console does not configure the bridge, so the user must do this before examining Slot 4 and Slot 5 registers.

For either bus, create a CPU address from the CPU base address (above), the function number of the device, and the offset into the PCI configuration space.

CPU address =
CPU base address +
function number * 256 +
offset

To read from this address use the SRM Console command

e -p {size} {CPU address}

where {size} is one of -l, -w, -b (for longword, word, or byte access) and {CPU address} is the address calculated above. For example, to read the STATUS register (offset 6, word wide) from the USB section (function 3) of the Cypress PCI-ISA bridge (primary bus, IDSEL hooked to AD<18>), the CPU address is (in hex)

801.FE00.3800 + 300 + 6 -> 801.FE00.3B06

and the console command is

e -p -w 801.FE00.3b06

ISA Bus

The Compaq AlphaStation XP1000 System has two built-in ISA devices as well as a slot for an additional ISA option (if the slot is not already occupied by a PCI device). The built-in devices are: