Product specifications

ProSavageDDR P4M266 – VT8751 P4 DDR SMA North Bridge
Revision 1.1, July 19, 2002 -27- Device 0 Register Descriptions
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Device 0 Host Bridge Device-Specific Registers
These registers are normally programmed once at system
initialization time.
V-Link Control
Device 0 Offset 40 – V-Link Specification ID (00h) ........RO
7-0 Specification Revision...................... always reads 00
Device 0 Offset 41 – NB V-Link Capability (18h) ...........RO
7-6 Reserved ........................................ always reads 0
5 16-bit Bus Width Supported ...............................RO
0 Not Supported ........................................default
1 Supported
4 8-Bit Bus Width Supported.................................RO
0 Not Supported
1 Supported ...............................................default
3 4x Rate Supported ...............................................RO
0 Not Supported
1 Supported ...............................................default
2 2x Rate Supported ...............................................RO
0 Not Supported ........................................default
1 Supported
1-0 Reserved ........................................ always reads 0
Device 0 Offset 42 – NB Downlink Command (88h) ......RW
7-4 DnCmd Max Request Depth (0=1 DnCmd) . def = 8
3-0 DnCmd Write Buffer Size (doublewords)..... def = 8
Device 0 Offset 44-43 – NB Uplink Status (8280h) ..........RO
15-12 UpCmd P2C Write Buffer Size (max lines).. def = 8
11-8 UpCmd P2P Write Buffer Size (max lines) .. def = 2
7-4 UpCmd Max Request Depth (0=1 UpCmd) . def = 8
3-0 Reserved ........................................ always reads 0
Device 0 Offset 45 –NB V-Link Bus Timer (44h)........... RW
7-4 Timer for Normal Priority Requests from SB
0000 Immediate
0001 1*4 VCLKs
0010 2*4 VCLKs
0011 3*4 VCLKs
0100 4*4 VCLKs ........................................... default
0101 5*4 VCLKs
0110 6*4 VCLKs
0111 7*4 VCLKs
1000 8*4 VCLKs
1001 16*4 VCLKs
1010 32*4 VCLKs
1011 64*4 VCLKs
11xx Own the bus for as long as there is a request
3-0 Timer for High Priority Requests from SB
0000 Immediate
0001 1*2 VCLKs
0010 2*2 VCLKs
0011 3*2 VCLKs
0100 4*2 VCLKs ........................................... default
0101 5*2 VCLKs
0110 6*2 VCLKs
0111 7*2 VCLKs
1000 8*2 VCLKs
1001 16*2 VCLKs
1010 32*2 VCLKs
1011 64*2 VCLKs
11xx Own the bus for as long as there is a request