Intel X38 User manual

Document Number: 318469-002
Intel®X38 Express Chipset
Memory Technology and
Configuration Guide
White Paper
January 2008

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Copyright © 2007 - 2008, Intel Corporation

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Contents
1Introduction.....................................................................................................5
2Technology Enhancements of Intel®Fast Memory Access (Intel®FMA) .....................6
2.1 Just in Time Command Scheduling............................................................6
2.2 Command Overlap..................................................................................6
2.3 Out of Order Scheduling..........................................................................7
2.4 Opportunistic Writes ...............................................................................7
3Supported Memory Technologies and Configurations..............................................8
3.1 Memory Technology Supported.................................................................8
3.2 DRAM Device Timing Support.................................................................10
3.3 ECC Support........................................................................................10
3.4 Valid Front Side Bus and Memory Speeds.................................................11
3.5 System Memory DIMM Configuration Support...........................................11
4Memory Organization and Operating Modes ........................................................12
4.1 Single-Channel Mode ............................................................................12
4.2 Dual Channel Modes .............................................................................12
4.2.1 Dual Channel Symmetric Mode..................................................12
4.2.2 Dual Channel Asymmetric Modes...............................................13
Tables
Table 3-1. Memory Technology Support Details.....................................................9
Table 3-2. DDR2 and DDR3 DRAM Device Timing Support.....................................10
Table 3-3. Intel®X38 Valid FSB/Memory Speed Configurations..............................11
Table 4-1. Sample Dual Channel Symmetric Organization Mode.............................13
Table 4-2. Sample Dual Channel Stacked Asymmetric Organization Mode................13
Table 4-3. Sample Dual Channel L-Shaped Asymmetric Organization Mode..............14

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Revision History
Revision
Number Description Revision Date
-001 Initial release October 2007
-002 Corrected DDR3 DIMM Module Support
Added Configuration details January 2008
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Introduction
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1Introduction
This document details the Intel®X38 Express Chipset system memory technology
enhancements, supported memory configurations, and memory organizations. It is
intended for a technical audience interested in learning about the performance
enhancements and simplified population rules offered by Intel®Fast Memory Access
and Intel®Flex Memory Technology in the platforms based on the Intel X38 Express
Chipset.

Technology Enhancements of Intel® Fast Memory Access (Intel® FMA)
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2Technology Enhancements of
Intel®Fast Memory Access
(Intel®FMA)
This chapter details Intel®X38 Express Chipset technology enhancements of its
memory controller known as Intel®Fast Memory Access (Intel®FMA). The memory
controller is located on the chipset’s 82X38 Memory Controller Hub (MCH) component.
With the growing reliance on faster and less latent memory technologies for today’s
high performance platforms, it has become necessary to not only increase system
memory transfer rate speeds, but to also streamline usage of the memory controller
protocol in novel and intelligent ways to decrease latency and optimize memory
bandwidth. To do this, several Intel technologies, known collectively as Intel®FMA,
have been included in this generation of Intel’s chipsets.
The following sections outline and explain the technology enhancements: Just In Time
Scheduling, Command Overlap, Out of Order Scheduling, and Opportunistic Writes.
2.1 Just in Time Command Scheduling
The Intel X38 Express Chipset has an advanced command scheduler where all pending
requests are examined simultaneously to determine the most efficient request to be
issued next. The most efficient request is picked from all pending requests and issued
to system memory Just In Time to make optimal use of Command Overlapping. Thus,
instead of having all memory access requests go individually through an arbitration
mechanism forcing requests to be executed one at a time, they can be started without
interfering with the current request allowing for concurrent issuing of requests. This
allows for the optimization of bandwidth and reducing of latency while retaining
system memory protocol.
2.2 Command Overlap
Command Overlap allows for the insertion of the DRAM commands between the
Activate, Precharge, and Read/Write commands normally used, as long as the inserted
commands do not affect the currently executing command. This allows for situations
where multiple commands can be issued in an overlapping manner, increasing the
efficiency of system memory protocol.

Technology Enhancements of Intel® Fast Memory Access (Intel® FMA)
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2.3 Out of Order Scheduling
Leveraging Just In Time Scheduling and Command Overlap, the Intel X38 Express
Chipset continuously monitors pending requests to system memory for the best use of
bandwidth and reduction of latency. If there are multiple requests to the same open
page, these requests would be launched in a back to back manner to make optimum
use of the open memory page. This ability to reorder requests on the fly allows the
Intel X38 Express Chipset to further reduce latency and increase bandwidth efficiency.
This is especially important for helping overcome the in-order manner of the Front
Side Bus between the Intel X38 Express Chipset and the processor to minimize
processor starvation.
2.4 Opportunistic Writes
Processor requests for memory reads usually are weighted more heavily than writes to
memory to avoid cases of starving the processor of data to process while the writes
are issued to system memory. Instead of having writes issued to a pending queue to
be flushed to memory when certain watermarks are reached, which could starve the
processor of data while it waits for the write flush to finish, the Intel X38 Express
Chipset monitors system memory requests and issues pending write requests to
memory at times when they will not impact memory read requests. This allows for an
almost continuous flow of data to the processor for processing.

Supported Memory Technologies and Configurations
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3Supported Memory
Technologies and
Configurations
3.1 Memory Technology Supported
The X38 Express Chipset supports the following DDR2 and DDR3 Data Transfer Rates,
DIMM Modules, and DRAM Device Technologies:
•DDR2 Data Transfer Rates:
⎯667 (PC2-5300) and 800 (PC2-6400)
•DDR3 Data Transfer Rates:
⎯800 (PC3-6400), 1067 (PC3-8500), and 1333 (PC3-10600)
•DDR2 DIMM Modules:
⎯Raw Card C - Single Sided x16 un-buffered non-ECC
⎯Raw Card D - Single Sided x8 un-buffered non-ECC
⎯Raw Card E - Double Sided x8 un-buffered non-ECC
⎯Raw Card F - Single Sided x8 un-buffered ECC
⎯Raw Card G - Double Sided x8 un-buffered ECC
•DDR3 DIMM Modules:
⎯Raw Card A - Single Sided x8 un-buffered non-ECC
⎯Raw Card B - Double Sided x8 un-buffered non-ECC
⎯Raw Card C - Single Sided x16 un-buffered non-ECC
•DDR2 and DDR3 DRAM Device Technology:
⎯512 Mb and 1 Gb

Supported Memory Technologies and Configurations
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Table 3-1. Memory Technology Support Details
Mem.
Type Raw Card
Ver.
DIMM
Cap. DRAM Device
Tech.
DRAM
Org. # of DRAM
Devices
# of
Physical
Device
Ranks
# of
Row /Col
Address
Bits
# of
Banks
Inside
DRAM
Page
Size
256 MB 512 MB 32M X 16 4 1 13/10 4 8K
C 512 MB 1 GB 64M X 16 4 1 13/10 8 8K
512 MB 512 MB 64M X 8 8 1 14/10 4 8K
D 1 GB 1 GB 128M X 8 8 1 14/10 8 8K
1 GB 512 MB 64M X 8 16 2 14/10 4 8K
E 2 GB 1 GB 128M X 8 16 2 14/10 8 8K
512 MB 512Mb 64M X 8 9 1 14/10 4 8K
F 1 GB 1Gb 128M X 8 9 1 14/10 8 8K
1 GB 512Mb 64M X 8 18 2 14/10 4 8K
DDR2
667
and
800
G 2 GB 1Gb 128M X 8 18 2 14/10 8 8K
512 MB 512 MB 64M X 8 8 1 13/10 8 8K
A 1 GB 1 GB 128M X 8 8 1 14/10 8 8K
1 GB 512 MB 64M X 8 16 2 13/10 8 8K
B 2 GB 1 GB 128M X 8 16 2 14/10 8 8K
256 MB 512 MB 32M X 16 4 1 12/10 8 8K
DDR3
800,
1067,
and
1333 C 512 MB 1 GB 64M X 16 4 1 13/10 8 8K

Supported Memory Technologies and Configurations
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3.2 DRAM Device Timing Support
The X38 Express Chipset supports the following DDR2 and DDR3 DRAM Device Speed
Bin and Write Latency (WL) Timings on the main memory interface.
Table 3-2. DDR2 and DDR3 DRAM Device Timing Support
Memory
Type DRAM Data Rate tCL t
RCD t RP WL Units
667 MT/s 5 5 5 4 tCK
800 MT/s 5 5 5 4 tCK
DDR2
800 MT/s 6 6 6 5 tCK
800 MT/s 5 5 5 5 tCK
800 MT/s 6 6 6 5 tCK
1067 MT/s 7 7 7 6 tCK
1067 MT/s 8 8 8 6 tCK
1333 MT/s 8 8 8 7 tCK
1333 MT/s 9 9 9 7 tCK
DDR3
1333 MT/s 10 10 10 7 tCK
3.3 ECC Support
For DDR3 the X38 Express Chipset does NOT support ECC, does not support ECC un-
buffered DIMMs, and it does not support any memory configuration that mixes non-
ECC with ECC un-buffered DIMMs.
For DDR2 the X38 Express Chipset does support ECC and ECC un-buffered DIMMs but
it does NOT support any memory configuration that mixes non-ECC with ECC un-
buffered DIMMs.
See Section 3.1 for un-buffered DIMM support details.

Supported Memory Technologies and Configurations
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3.4 Valid Front Side Bus and Memory Speeds
The X38 Express Chipset supports the following Front Side Bus (FSB) and system
memory speed configurations.
Table 3-3. Intel®X38 Valid FSB/Memory Speed Configurations
Memory
Type FSB DRAM Data Rate Single
Channel Peak
Bandwidth
Dual Channel
Peak
Bandwidth
1333
MHz 800 MT/s 6.4 GB/s 12.8 GB/s
1333
MHz 667 MT/s 5.3 GB/s 10.6 GB/s
1067
MHz 800 MT/s 6.4 GB/s 12.8 GB/s
1067
MHz 667 MT/s 5.3 GB/s 10.6 GB/s
800 MHz 800 MT/s 6.4 GB/s 12.8 GB/s
DDR2
800 MHz 667 MT/s 5.3 GB/s 10.6 GB/s
1333
MHz 1333 MT/s 10.5 GB/s 21.0 GB/s
1333
MHz 1067 MT/s 8.5 GB/s 17.0 GB/s
1333
MHz 800 MT/s 6.4 GB/s 12.8 GB/s
1067
MHz 1067 MT/s 8.5 GB/s 17.0 GB/s
1067
MHz 800 MT/s 6.4 GB/s 12.8 GB/s
DDR3
800 MHz 800 MT/s 6.4 GB/s 12.8 GB/s
Note: The X38 Express Chipset does not support system memory frequencies that exceed
the frequency of the Front Side Bus. If memory with higher frequency capabilities than
that of the FSB is populated, the memory will be under-clocked to align with the FSB.
3.5 System Memory DIMM Configuration Support
The X38 Express Chipset directly supports one or two channels of DDR2 or DDR3
memory with the following DIMM configurations:
⎯Supports one or two DDR2 or DDR3 DIMM modules per channel.
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Memory Organization and Operating Modes
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4Memory Organization and
Operating Modes
The Intel X38 Express Chipset memory interface is designed with Intel®Flex Memory
Technology so that it can be can be configured to support single-channel or dual-
channel DDR2 or DDR3 memory configurations. Depending upon how the DIMMs are
populated in each memory channel, a number of different configurations can exist for
DDR2 or DDR3.
The following sections explain and show the different memory configurations that are
supported by the X38 Express Chipset.
4.1 Single-Channel Mode
In this mode, all memory cycles are directed to a single channel.
Single channel mode is used when either Channel-0 or Channel-1 DIMMs are
populated in any order, but not both.
4.2 Dual Channel Modes
4.2.1 Dual Channel Symmetric Mode
This mode provides maximum performance on real applications. Addresses are ping-
ponged between the channels after each cache line (64 byte boundary). If there are
two requests, and the second request is to an address on the opposite channel from
the first, that request can be sent before data from the first request has returned. If
two consecutive cache lines are requested, both may be retrieved simultaneously,
since they are ensured to be on opposite channels.
Dual channel symmetric mode is used when both Channel-0 and Channel-1 DIMMs are
populated in any order with the total amount of memory in each channel being the
same, but the DRAM device technology and width may vary from one channel to the
other.
Table 4-1 is a sample dual channel symmetric memory configuration showing the rank
organization.

Memory Organization and Operating Modes
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Table 4-1. Sample Dual Channel Symmetric Organization Mode
Rank Channel 0
Population Cumulative Top Address in Channel 0 Channel 1 Population Cumulative
Top Address
in Channel 1
Rank 3 0 MB 2560 MB 0 MB 2560 MB
Rank 2 256 MB 2560 MB 256 MB 2560 MB
Rank 1 512 MB 2048 MB 512 MB 2048 MB
Rank 0 512 MB 1024 MB 512 MB 1024 MB
4.2.2 Dual Channel Asymmetric Modes
4.2.2.1 Stacked Asymmetric Mode
In this addressing mode addresses start in channel-0 and stay there until the end of
the highest rank in channel-0, and then addresses continue from the bottom of
channel-1 to the top.
This mode is used when both Channel-0 and Channel-1 DIMMs are populated in any
order with the total amount of memory in each channel being different.
Table 4-2 is a sample dual channel stacked asymmetric memory configuration
showing the rank organization.
Table 4-2. Sample Dual Channel Stacked Asymmetric Organization Mode
Rank Channel 0
Population Cumulative
Top Address in
Channel 0 Channel 1
Population Cumulative
Top Address
in Channel 1
Rank 3 0 MB 1280 MB 0 MB 2304 MB
Rank 2 256 MB 1280 MB 0 MB 2304 MB
Rank 1 512 MB 1024 MB 512 MB 2304 MB
Rank 0 512 MB 512 MB 512 MB 1792 MB

Memory Organization and Operating Modes
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4.2.2.2 L-shaped Asymmetric Mode
In this addressing mode the lowest DRAM memory is mapped to dual channel
operation and the top most DRAM memory is mapped to single channel operation. In
this mode the system can run at one zone of dual channel mode and one zone of
single channel mode simultaneously across the whole memory array.
This mode is used when both Channel-0 and Channel-1 DIMMs are populated in any
order with the total amount of memory in each channel being different.
Table 4-3 is a sample dual channel L-shaped asymmetric memory configuration
showing the rank organization.
Table 4-3. Sample Dual Channel L-Shaped Asymmetric Organization Mode
Rank Channel 0
Population Cumulative
Top Address in
Channel 0 Channel 1
Population Cumulative
Top Address
in Channel 1
Rank 3 0 MB 2048 MB 0 MB 2304 MB
Rank 2 0 MB 2048 MB 256 MB 2304 MB
Rank 1 512 MB 2048 MB 512 MB 2048 MB
Rank 0 512 MB 1024 MB 512 MB 1024 MB
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