--- wikisrc/users/rkujawa/g-rex.mdwn	2012/07/06 19:30:50	1.4
+++ wikisrc/users/rkujawa/g-rex.mdwn	2012/07/06 19:46:52	1.5
@@ -2,7 +2,7 @@
 
 Programming the G-REX PCI bridge
 
-document version 0.1 - THIS IS A WORK IN PROGRESS!
+document version 0.2 - THIS IS A WORK IN PROGRESS!
 
 # 0. Introduction
 
@@ -29,6 +29,10 @@ Firmware does the dirty job of assigning
 etc.) before the OS is running. Therefore G-REX does not need any special 
 initialization.
 
+All memory spaces of G-REX are directly visible and addressable in Amiga memory
+space, unlike in Mediator. Firmware allocates memory space as needed, depending
+on what cards are installed.
+
 # 2. Memory map
 
 G-REX is configured as multipie AutoConf boards. Confusingly, they all have the same vendor (8512) and product (101).
@@ -58,8 +62,11 @@ CVPPC/BVPPC there's aslo a mirror on +0x
 
 This space offers access to I/O registers of all PCI cards.
 
-BAR addresses in this space are treated as relative to 0xFFFA0000. Card with 
-I/O BAR set to 0x100 will actually be available at 0xFFFA0100. 
+On G-REX BAR addresses in this space are treated as absolute.
+
+On CVPPC/BVPPC BAR addresses in this space are treated as relative to 
+0xFFFA0000. Card with I/O BAR set to 0x100 will actually be available 
+at 0xFFFA0100. 
 
 # 2c. PCI memory space (0x80000000)
 
@@ -71,7 +78,9 @@ For example Voodoo 3, which has two 32MB
 two 8512/101 boards somewhere at 0x80000000 (or later).
 
 Addresses in this space are treated as absolute. Memory BAR register set to 
-0x80000000 means it is configured at this address.  
+0x80000000 means it is configured at this address.
+
+On CVPPC/BVPPC this space is present at different address - 0xE0000000.
 
 # 2d. Bridge configuration registers
 
@@ -83,7 +92,7 @@ Offset - meaning
 
 No need to fiddle with these registers, as they've been already configured properly by the firmware.
 
-# 3. Reconfiguring the bus.
+# 3. Reconfiguring the bus
 
 If needed, it's possible to reconfigure bus just by writing new values into 
 configuration space. Keep in mind that any previously initialized chips will 
@@ -93,17 +102,19 @@ initialized by the firmware so it can di
 # 4. Interrupts
 
 All interrupts are converted into Amiga INT2 interrupt. There's no such thing 
-as interrupt acknowledge register.
+as interrupt acknowledge register. However, there seems to be an interrupt 
+enable register (see "Bridge configuration registers" above).
 
 # 5. DMA
 
-The bridge is certainly capable of DMA, but it needs further reverse 
-engineering.
+The bridge is certainly capable of real busmaster DMA, but it needs further 
+reverse engineering.
 
 [TO BE COMPLETED]
 
 There were at least two different revisions of G-REX 1200. Later revision 
-probably does support DMA in two slots.
+probably does support DMA in first two slots. I'm not sure if it is possible
+to detect revision of the G-REX in software.
 
 G-REX 4000D probably has busmaster DMA capability in all slots.