IBM System x3950 M2 and x3850 M2 Technical Introduction
15
Figure 7 x3850 M2 and x3950 M2 system block diagram
Each memory port out of the memory controller has a peak read throughput of 4.26 GBps and
a peak write throughput of 2.13 GBps. DIMMs are installed in matched pairs, two-way
interleaving, to ensure the memory port is fully utilized. Peak throughput for each PC2-5300
DDR2 DIMM is 4.26 GBps.
Because there are eight memory ports, spreading installed DIMMs across all four memory
ports can improve performance. The eight independent memory ports provide simultaneous
access to memory. With four memory cards installed, and eight DIMMs in each card, peak
read memory bandwidth is 34.1 GBps and peak write bandwidth is 17.1 GBps.
The memory controller routes all traffic from the eight memory ports, four microprocessor
ports, and the three PCI bridge ports. The memory controller also has embedded DRAM
which, in the x3850 M2 and x3950 M2, holds a snoop filter lookup table. This filter ensures
that snoop requests for cache lines go to the appropriate microprocessor bus and not all four
of them, thereby improving performance.
As shown in Figure 7, PCI bridge 1 supplies four of the seven PCI Express x8 slots on four
independent PCI Express buses. PCI bridge 2 supplies the other three PCI Express x8 slots
plus the onboard SAS devices, including the optional ServeRAID-MR10k. A separate South
bridge supplies all the other onboard PCI devices, such as the USB ports, onboard Ethernet
and the standard RSA II.
B = bytes
b = bits
Seven PCI Express x8 slots
(slots 6 & 7 are hot-swap)
IBM X4
Architecture
core chipset
6
5
4
3
HDD backplane
Each FSB:
1066 MHz
8.53 GBps
8 ports, each:
R: 4.26 GBps
W: 2.13 GBps
HSS-IB 6 GBps
Serial
Scalability ports
10.24 GBps each
7
2
1
MR10k
External SAS port
LSI
1078
SAS
IDE DVD
6x USB 2.0
PCI +
USB
PCI-E x4
2 GBps
South bridge
DDR2
Buffer
DDR2
Buffer
DDR2
Buffer
DDR2
Buffer
DDR2
Buffer
DDR2
Buffer
DDR2
Buffer
DDR2
Buffer
PCI-E bridge 1
PCI-E bridge 2
Memory
controller
("Hurricane 4")
CPU 2
CPU 3
CPU 1
CPU 4
Gb Ethernet
BCM5709C
RSA2 +
Video
HSS-IB 6 GBps