Gxb Error Flow - Intel 460GX Software Developer’s Manual

•
PCI Outbound Write Que Data Parity Error - This error signifies that either a) data was
received from the Expander bus with bad parity or b) the OB write Que was corrupted. As data
is read from the queue and passed to the PCI bus, the parity is checked.
•
AGP Low-priority Read Data Que Parity Error - This error signifies that either a) data was
received from the Expander bus with bad parity or b) the read Que was corrupted. As data is
read from the queue and passed to the AGP bus, the parity is checked.
•
AGP Hi-priority Read Data Que Parity Error - This error signifies that either a) data was
received from the Expander bus with bad parity or b) the read Que was corrupted. As data is
read from the queue and passed to the AGP bus, the parity is checked.
•
PCI Inbound Read Que Data Parity Error - This error signifies that either a) data was received
from the Expander bus with bad parity or b) the read Que was corrupted. As data is read from
the queue and passed to the AGP bus, the parity is checked. This is for PCI reads done by the
graphics card. The parity on the PCI data will be poisoned out to the card as the data is
returned.
6.11.4.3 Multiple Errors
In the case that 2 or more errors occur at the same cycle, multiple bits are set in the FERR register.
This should be an extremely rare case. Software can read the register and check that only one bit is
set. The data that is captured along with the error is indeterminate. Since there are multiple
registers for error data, 2 errors may cause the Expander and PCI error registers to have valid data.
Or, if there were 2 errors from Expander bus at the same time, then the Expander data-error register
may have been set by either error.
Figure 6-3. GXB Error Flow
Intel® 460GX Chipset Software Developer's Manual
SAC
SAC
UpS
DnS
Data
Data
Pass data to SAC with
parity from queue, don't
Place data into buffer check outgoing parity.
with parity as received from
Expander (16 data, 2 BE, 1 par.)
AGP AGP
PCI
High Low
IB
Write
Write Write
Data Data
Data
AGP
PCI PCI
AGP
Generate parity
Low IB OB
High
in Expander format,
Read
Read Read Write
data and BE. If
Data Data Data
Data
PCI data is bad,
poison into
buffer.
Check Parity.
If PCI, then corrupt outgoing parity.
Data Integrity and Error Handling
SAC Interconnect
Check parity.
On HDR: BINIT#. Drop
PKT and data. Set FERR.
SAC
OB
AGP
PCI
LO
IB
PCI
OB
Read
Data
GART
PCI AGP
IB Low
CFG
PCI
Ctrl
OB
AGP Bus
SAC
IB
AGP
HI
SRAM
Chk parity.
AGP
High
AGP
Que
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