At this time, there are no known errata to this release of the reference design.
A modification has been made to simplify the configuration of the motherboard (see Section
1.1).
The following is a history of reference design releases:
- Release 4.0 of the reference design features the enhanced Cheetah3 CPU card.
- Release 3.0 of the reference design incorporated the workarounds that were
required for the errata found on release 1.0 of the reference design.
- There was no release 2.0 of the reference design.
- Release 1.0 was the initial release of the reference design.
1.1 Configuration For 603 1:1 or 3:2 Mode
The IBM27-82660 PowerPC to PCI Bridge and Memory Controller (660) includes a
strapping option which indicates to the 660 when it is being used with a 603 family CPU
operating with a 1:1 or 3:2 CPU core:bus clock ratio. On the reference design motherboard,
the strapping option was originally set by populating or unpopulating a pair of resistors.
Since this option requires soldering, a more user-friendly method was devised.
1.1.1 Setting The 603 1:1 Mode Jumper
The three pin J35 jumper connector on the motherboard (see Figure 1) now sets the
strapping option. As shown in Table 1, set the jumper to connect J35 pin 1 to pin 2 for CPU
cards featuring a 603e, or 603ev operating with either a 1:1 or 3:2 CPU core:bus clock ratio.
Set the jumper to connect J35 pin 2 to pin 3 for 604 family operation or for 603 family
operation at 2:1 or greater.
| Table 1. J35 Setting
|
| CPU Type
|
CPU Core:Bus Ratio
|
J35 Setting
|
| 603e, 603ev
|
1:1 or 3:2
|
1-2
|
| 603e, 603ev
|
Not (1:1 or 3:2)
|
2-3
|
| 604, 604ev1, 604ev2
|
All
|
2-3
|
1.1.2 Schematic Changes
Figure 2 shows the changes to page 11 of the reference design schematic. The grounded
end of R347 has been removed from ground by cutting the trace, and that end of R347 has
been attached to J35 pin 2. Note that R766 has not been populated.
Figure 3 shows the changes to page 32 of the reference design schematic. The wire from
R347 attaches to pin 2 of J35. Also note that R897 is not populated. The section of U25
which is attached to J35 has no function in the supplied configuration of the motherboard.
U25 also has no ill effect upon the circuit.
The electrical effect of the modification is to provide an 11k pullup on MWS_P2MRXS#
while J35 pin 1 is connected to pin 2, and to provide a 1K pulldown on MWS_P2MRXS#
while J35 pin 2 is connected to pin 3.
