Introduction
System Board Components
Chapter 1
24
This design does not support any non industry standard DDR DIMMs. Only qualified DIMMs are supported.
Figure 1-5 shows a block diagram of the server memory.
Figure 1-5 Memory Block Diagram
Memory Architecture
The I/O ASIC memory interface supports two DDR cells, each of which is 144 data bits wide. The memory
subsystem physical design uses a comb-filter termination scheme for both the data and the address and
control buses. This part of the topology is similar to other DDR designs in the computer industry. Clocks are
distributed directly from the I/O ASIC; each clock pair drives two DIMMs.
Memory data is protected by the ECC. Eight ECC bits per DIMM protect 64 bits of data. The use of ECC
allows correction of single-bit errors, and detection of multi-bit errors. Only DIMMs with ECC are qualified or
supported.
DIMMs
The memory subsystem supports only DDR SDRAM (Double Data Rate Synchronous Dynamic Random
Access Memory) technology utilizing industry-standard PC-1600 type DDR SDRAM DIMMs, 1.2" tall. The
DIMMs use a 184-pin JEDEC standard connector.
Memory
Controller
DIMM1B
MC1
MC0
CS1(0)
CS1(4)
SA0=1
SA1=0
SA2=0
SA0=1
SA1=0
SA2=1
SA0=1
SA1=1
SA2=0
SA0=0
SA1=0
SA2=0
SA0=0
SA1=0
SA2=1
SA0=0
SA1=1
SA2=0
SA0=0
SA1=1
SA2=0
SA0=0
SA1=0
SA2=1
SA0=0
SA1=0
SA2=0
SA0=1
SA1=1
SA2=0
SA0=1
SA1=0
SA2=1
SA0=1
SA1=0
SA2=0
DIMM0B
CS1(0)
CS1(4)
DIMM4B
CS1(2)
CS1(6)
DIMM2B
CS1(1)
CS1(5)
DIMM0A
CS1(0)
CS1(4)
DIMM4A
CS1(2)
CS1(6)
DIMM2A
CS1(1)
CS1(5)
CS1(2)
CS1(6)
CS1(1)
CS1(5)
CS1(0)
CS1(4)
CS1(2)
CS1(6)
CS1(1)
CS1(5)
DIMM5B
DIMM3B
DIMM1A
DIMM5A
DIMM3A
Stub Isolation Resistors for Address and Control Rs=18 ohms
Stub Isolation Resistors for DQ[71:0] and associated DQS Rs=18 ohms
Parallel Termination Resistors for Address and Control Rt=27 ohms
Parallel Termination Resistors for DQ[143:72] and associated DQS Rt=27 ohms
DIMM CLK Stub Isolation Resistors Rs=0 ohms
DIMM CLK Stub Isolation Resistors Rs=0 ohms
DIMM CLK Stub Isolation Resistors Rs=0 ohms
Stub Isolation Resistors for DQ[143:72] and associated DQS Rs=18 ohms
Same connection scheme
for MC1 as for MC0
Parallel Termination Resistors for DQ [71:0] and associated DQS Rt=27 ohms
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