This chapter describes the function and physical components of the compute module. It also describes the possible system configurations and the technical specifications for this module. Specifically, this chapter includes the following information.
Two types of compute modules are available for the SGI 350 server system, as follows:
Base compute module. This module is your system's primary compute module where your server system's operating system resides. (Every system must have a base compute module.) The base compute module provides processors, memory, and PCI/PCI–X slots to connect I/O devices. It also comes standard with a factory–installed SCSI disk drive, and an IO9 card and a serial daughtercard that provide various I/O ports to your system.
System expansion compute module. This module, in contrast to the base compute module, comes with processors, memory, and PCI/PCI–X slots, but the SCSI disk drive and the IO9 card are optional.
Note: In this chapter, the term “compute module” refers to both types of compute modules, so remember that some of the features that are standard for the base compute module are optional for the system expansion compute module. When information is applicable to only one of the two types of modules, that will be specified.
This 2U base compute module can serve as a standalone Origin 350 server system, or it can be rackmounted with other optional modules to create an Origin 350 server system with more functionality. The base compute module consists of 2 to 4 64-bit MIPS RISC (reduced instruction set computer) processors and from 1 to 8 GB of local memory available on two to eight dual inline memory modules (DIMMs).
To expand the function of the system, you can combine this base compute module with one or more of the following optional modules:
The system expansion compute module, which is interconnected to the base compute module via a NUMAlink 3 cable, adds processors, memory, and four PCI and PCI-X card slots to your system. It may or may not include an IO9 card. If it includes an IO9 card, it will take up the lowermost PCI/PCI–X slot. (The new combined single system created by connecting the base compute module with a system expansion compute module can include 4, 6, or 8 processors with local memory of up to 16 GB.)
The 4U PCI expansion module adds PCI slots, but no processors, no memory, and no IO9 card. There are two versions of the PCI expansion module: one module has 12 PCI slots that support 3.3-V or universal PCI cards, and the other module has 6 PCI slots that support 5-V or universal PCI cards and 6 slots that support 3.3-V or universal PCI cards. For more information about this module, see the PCI Expansion Module User's Guide (5.0-V Support and/or 3.3-V Support) (007-4499-00x).
The 2U memory and PCI expansion (MPX) module can provide extra memory and four PCI/PCI-X card slots for your system. See Chapter 4, “Memory and PCI Expansion (MPX) Module” for more information about this module.
The SGI TP900 storage module, can provide additional storage for the system. See SGI Total Performance 900 Storage System User's Guide (007-4428-00x) for information about this module. The Origin 350 server system supports other storage modules. See “Storage Expansion” in Chapter 2 for information.
The NUMAlink module connects two or more compute modules. See Chapter 5, “NUMAlink Module” for more information about this module.
Figure 3-1 shows front panel and side views of the compute module.
The compute module includes the following features:
L1 controller, which manages and monitors functions of the compute module such as system temperature. The module includes an L1 controller display, which displays system processes and error messages.
Optional internal read-only slim–line DVD–ROM drive, and two hard disk drives.
One or two power supplies. The second power supply, which is optional, is redundant to assure that your compute module will always have power.
NUMAlink 3 port, which connects your system to a system expansion compute module, an MPX module, or a 4U PCI expansion module.
Crosstown2 XIO port is supported, which enables the server system to connect to an InfiniteReality graphics pipeline.
Four PCI/PCI–X card slots on two busses. These 64-bit slots can contain 33-MHz and 66-MHz PCI cards, or 66-MHZ and 100-MHz PCI–X cards. Your base compute system comes standard with an IO9 PCI card that is installed in the lowermost of these slots.
Note: Because the IO9 card is a PCI card that runs at 66 MHz, the slot in the same bus as the IO9 card (bus 1, slot 2) can only run in PCI mode and no faster than 66 MHz. Two DB–9 serial ports. One labeled L1 console port (console and diagnostic port) enables you to connect a system console to the L1 controller on the compute module. The other, labeled Serial port 1, connects a serial device such as a printer or modem to the compute module.
Type B USB (Universal Serial Bus) L1 port, which connects the compute module to an L2 controller.
Factory-installed serial daughtercard (in the base compute module), which includes the following:
Three DB-9 serial ports, which connect RS–232/RS–422 serial devices, such as modems or printers, to the server system.
Two PS/2 connectors, one to connect a PS/2 keyboard, and one to connect a PS/2 mouse.
IO9 card, which provides the following connectors and functions to your compute module:
Real-time interrupt input (RTI) port, and real-time interrupt output (RTO) port.
10/100/1000 BaseT Ethernet port.
68-pin VHDCI Ultra3 SCSI connector.
Table 3-1 compares an Origin 300 server system with an Origin 350 server system, and highlights the expanded functionality of the compute module.
Table 3-1. Comparing Origin 300 Server System with Origin 350 Server System
System Feature | Origin 300 Server System | Origin 350 Server System |
|---|---|---|
MIPS RISC processors | 2 or 4 | 2 or 4 |
Memory | 512 MB to 4 GB | 1 GB to 8 GB |
I/O expansion slots | Two 64-bit slots for 33 MHz or 66 MHz PCI cards. | Three 64–bit slots for 33 MHz or 66 MHz PCI cards, and two 66 MHz or 100 MHz PCI–X cards.[a] |
Serial ports | 2 DB-9 RS-232 or RS-422 serial ports. | 4 DB-9 RS-232 or RS-422 serial ports |
Console port | 1 DB–9 serial console port to connect a console to the server. | 1 DB–9 serial console port to connect a console to the server. |
3.5-inch drive bays | 2 | 2 |
DVD–ROM (read-only) | None | 1 |
USB type A ports | 2 USB type A ports to connect keyboard and mouse. | None |
PS/2 ports | None | 2 PS/2 ports to connect keyboard and mouse. |
L1 port (USB type B) | 1 L1 port (USB type B) to connect the server to the L2 controller. | 1 L1 port (USB type B) to connect the server to the L2 controller. |
NUMAlink port | 1 | 1 |
XIO port | 1 | 1 |
Power supplies | 1 | 2 (one power supply is redundant). |
Ethernet port | One 10BaseT/100BaseT port | One 10BaseT/100BaseT/1000BaseT port |
SCSI channel (internal) | 1 Ultra3 SCSI, 160 MB/s | 1 Ultra3 SCSI, 160 MB/s |
SCSI channel (external) | 1 Ultra3 SCSI (VHDCI) | 1 Ultra3 SCSI (VHDCI) |
RT interrupt input and output ports | 1 input and 1 output | 1 input and 1 output |
[a] This system has three (and not four) card slots available because the lowermost slot is used for a factory–in stalled IO9 card. Also, the number of slots available for PCI and PCI–X cards and for cards of different speeds differs because the IO9 card is a 66 MHz PCI card, which limits the slot located in the same bus as the IO9 card to operate in PCI mode with a speed of 66 MHz or less. | ||
The compute module architecture includes the following components, which are shown in Figure 3-2 and discussed in the following subsections:
The IP53 node board consists of the following components, most of which are discussed in the subsections that follow.
Two or four MIPS RISC processors (labeled CPU in Figure 3-3). Each processor has a secondary L2 cache.
Primary and secondary (L2) cache. (The primary cache is internal to the processor. The L2 cache is labeled SRAM in Figure 3-3.)
Eight dual inline memory module (DIMM) slots, for installation of DIMMs to provide 1 to 8 GB of main memory to local memory bank pairs on your server. See “Local Memory (DIMMs)”, for more information about DIMMs.
Bedrock ASIC (or hub ASIC), which enables communication between the processors, memory, and I/O devices.
Serial ID EEPROM, which contains component information.
Three VRMs, which convert incoming voltages to voltages required by components.
The R16000 processors, which are soldered to the IP53 node board, implement the 64-bit MIPS IV instruction set architecture. The architecture gathers and decodes four instructions per cycle and issues the instructions to five fully pipelined execution units. It predicts conditional branches and executes instructions along the predicted path.
Each processor also uses a load/store architecture in which the processor does not operate on data located in memory; instead, it loads the memory data into its registers and then operates on the data. When the processor is finished manipulating the data, the processor stores the data in memory.
To reduce memory latency, a processor has access to two on-chip 32-KB L1 (primary) caches (one cache is for data and the other cache is for instructions) and an off-chip L2 (secondary) cache. The L1 caches are located within the processor for fast, low-latency access of instructions and data. The compute module supports a 4-MB L2 cache.
| Note: The IP53 node boards use SECDED ECC to protect data when transferred to and from secondary cache, main memory, and directory memory. |
The IP53 node boards use parity to protect data when transferred between a processor and primary cache, and to protect system commands sent between the Bedrock ASIC and a processor.
Each compute module has from 1 to 8 GB of local memory, which includes main memory and directory memory for cache coherence.
Local memory is provided by DIMMs, which contain double data rate synchronous dynamic random-access memory (DDR SDRAM chips), installed in two or more DIMM slots located on the compute module.
These eight DIMM slots are laid out into one group of even–numbered slots 0, 2, 4, and 6, and a second group of odd-numbered slots 1, 3, 5, and 7, as shown in Figure 3-4.
DIMMs are installed or removed one per DIMM slot, and two at a time, so that the two DIMMs installed provide local memory, or remove local memory, for the same pair of banks. For example, you could install a DIMM in slot 0 and another in slot 1 to provide local memory for banks 0 and 1. And conversely, you could remove a DIMM from slot 0 and another from slot 1 in order to remove local memory from banks 0 and 1.
| Note: The two DIMMs that compose a bank pair must be the same size; however, the bank pairs can differ in memory size. |
Table 3-2 lists the DIMM slots and the corresponding bank pairs to which local memory is provided when DIMMs are installed:
Table 3-2. DIMMs and Bank Pairs
DIMM in Slot Number | Provides Local Memory for Bank Pair Numbers |
|---|---|
0[a] | 0 and 1 |
1 | 0 and 1 |
2 | 2 and 3 |
3 | 2 and 3 |
4 | 4 and 5 |
5 | 4 and 5 |
6 | 6 and 7 |
7 | 6 and 7 |
[a] The first two DIMMs must be installed in DIMM slot 0 and DIMM slot 1. | |
Table 3-3 lists the DIMM sizes that the IP53 node boards support.
Table 3-3. Memory DIMM Specifications
DIMM Capacity | Chip Capacity | Total Memory Capacity |
|---|---|---|
512 MB | 128 MB | 2 DIMMs (1 bank pair): 1 GB 8 DIMMs (4 bank pairs): 4 GB |
1 GB | 256 MB | 2 DIMMs (1 bank pair): 2 GB 8 DIMMs (4 bank pairs): 8 GB |
The Bedrock ASIC enables communication among the processors, memory, network, and I/O devices. It controls all activity within the node board (for example, error correction and cache coherency). The Bedrock ASIC also supports page migration.
The Bedrock ASIC consists of the following:
A central crossbar (XB) provides connectivity between the Bedrock ASIC interfaces.
Each of two processor interfaces (PI_0 and PI_1) communicates directly with two processors. If the node board contains two processors, only one processor interface is used.
A memory/directory interface (MD) controls all memory access.
A network interface (NI) is the interface between the crossbar unit and the NUMAlink 3 interconnect.
An I/O interface (II) allows I/O devices to read and write memory (direct memory access [DMA] operations) and allows the processors within the system to control the I/O devices (PIO operations).
A local block (LB) services processor I/O (PIO) requests that are local to the Bedrock ASIC.
The IO9 PCI card, which resides in bus 1, slot 1 (the lowermost slot) of the base compute module, provides the base I/O functionality for the system.
| Note: The expansion compute module can be ordered with an IO9 PCI card. This card resides in bus 1, slot 1. |
The IO9 PCI card has the following connectors:
External VHDCI 68-pin SCSI connector.
10/100/1000BaseT Ethernet connector.
Real-time interrupt output (RTO) connector, and real-time interrupt input (RTI) connector.
The IO9 card also contains an IOC-4 ASIC that supports the following features:
One IDE channel for the DVD-ROM.
Four serial ports.
Two PS/2 ports for keyboard and mouse connections.
Note: The PS/2 ports and three serial ports are located on a daughtercard that is only available on a base compute module. NVRAM and time-of-day clock.
The interface board contains the following components:
L1 controller logic.
Power supply interface.
IO9 expansion connectors. Each of these connects to the serial daughtercard that contains DB-9 connectors (serial ports) and DIN-6 connectors (PS/2 ports).
NUMAlink connector.
XIO connector.
Switch regulators.
Connectors to the IP53 node board and the PCI riser card.
The PCI riser card provides the following:
PIC ASIC.
Connectors that connect the PCI riser card to the interface board.
Nonstandard PCI/PCI–X connector that connects to the IO9 card.
Four PCI/PCI–X card slots (64 bit, 3.3 V) and a slot for a VPro V12 graphics board. (The slot for the VPro V12 graphics board is located on the backside of the PCI riser card.)
The compute module can contain an optional slim-line DVD-ROM that has CD-ROM capabilities.
| Note: The DVD-ROM requires an IO9 PCI card. |
The DVD-ROM is located at the front left side of the module (above the disk drives).
The base compute module supports one or two sled-mounted Ultra3 SCSI disk drives that have a peak data transfer speed of up to 160 MB/s between the disks and system memory. The two disks connect to a SCSI backplane. The SCSI backplane connects to the internal SCSI 160 logic on the IO9 PCI card.
| Note: An expansion compute module can also be ordered with SCSI disk drives. This configuration requires an IO9 PCI card. |
Two disk drive sizes are available, as follows:
18-GB 15,000-RPM disk drive
73-GB 10,000-RPM disk drive
The disk drives are located at the front left side of the module (below the DVD-ROM). The master drive is the bottom drive.
The compute module can contain one or two power supplies; the second power supply is optional and is required only when the customer wants redundant power. The power supply can input 110/220 VAC and output 500 W (12 VDC, 5 VDC, and -12 VDC.
Both power supplies are hot–swappable. They are located at the front right side of the module. The primary power supply is the left supply, and the redundant power supply is the right supply.
This section describes the external components of the compute module, which are located in the front and rear panels.
This section describes the front panel controls and indicators of the compute module, as shown in Figure 3-5.
The front panel of the compute module has the following items:
L1 controller display. A liquid crystal display (LCD) displays status and error messages that the L1 controller generates.
Note: See the SGI L1 and L2 Controller Software User's Guide (007-3938-00x) for more information on the L1 controller. Power button with LED. Press this button to power on the internal components. Alternatively, you can power on the internal components at a system console. The LED illuminates green when the internal components are on.
Reset button. Press this button to reset the internal processors and ASICs. The reset will cause a memory loss. (To perform a reset without losing memory, see the NMI button information that follows.)
NMI button. Press the NMI (non-maskable interrupt) button to reset the internal processors and ASICs without losing memory. Register data and memory are stored in a /var/adm/crash file.
Service-required LED. This LED illuminates yellow to indicate that an item has failed or is not operating properly, but the compute module is still operating.
Failure LED. This LED illuminates red to indicate that a failure has occurred and that the compute module is down.
This section describes the rear panel connectors, PCI/PCI–X slots, and LEDs of the compute module, as shown in Figure 3-6.
The rear panel of the compute module has the following items:
Power connector. This connector connects the base compute module to an AC power outlet.
Console port. This DB–9 serial port (console and diagnostic port) enables you to connect a system console to the L1 controller on the compute module.
Serial port 1. This DB-9 RS-232/RS-422 serial port connects a serial device, such as a printer or modem, to the compute module.
L1 port (USB type B). This Universal Serial Bus (USB) type B connector connects the compute module's L1 controller to an L2 controller.
XIO connector. This Crosstown2 connector connects the base compute module to an InfiniteReality graphics pipeline. This connection is made with a NUMAlink 3 cable at 800 MB/s in each direction.
XIO connector LEDs. The XIO connector has two LEDs. These LEDs are located to the right of the XIO connector. One LED lights yellow to indicate that both the compute module and the InfiniteReality graphics pipeline to which the compute module is connected are powered on. The other LED lights green when the compute module link to the graphics pipeline is established.
NUMAlink connector. This NUMAlink 3 connector connects the base compute module to one of the following modules: expansion compute module, NUMAlink module, PCI expansion module, or MPX module. This connection is made with a NUMAlink 3 cable at 1.6 GB/s in each direction.
NUMAlink 3 LED. The NUMAlink 3 connector has two LEDs. These LEDs are located to the right of the NUMAlink 3 connector. One LED lights yellow to indicate that the compute module and the module to which it is connected are powered on. The other LED lights green when the link between the compute module and the module to which it is connected is established.
PCI/PCI–X slots (bus 1, slot 1; bus 1, slot 2; bus 2, slot 1; bus 2, slot 2). These slots are labeled from bottom to top PCI 1, PCI 2, PCI 3, and PCI 4. Two of these slots are on one bus, and two slots are on another. These 64-bit slots can contain 33-MHz and 66-MHz PCI cards, and 66-MHz and 100-MHz PCI–X cards. (For an updated list of supported cards, see SGI Supportfolio at http://support.sgi.com.) The bottom-most slot contains an IO9 PCI card in the base compute module.
Note: If you run PCI and PCI–X cards on the same bus at the same time, the PCI–X card will run on PCI mode. And if you run cards of different speeds on the same bus, the highest-speed card will run at the speed of the slower card. For example, if a card is running at 100 MHz in one slot of a bus, and a card is running at 33 MHz in the second slot of the same bus, both cards will run at 33 MHz.
The factory-installed serial daughtercard (only available on the base compute module) provides the following connectors:
Two PS/2 ports (keyboard and mouse). These ports connect a PS/2 keyboard and mouse to the system.
Serial ports 2, 3, and 4. These three DB-9 RS-232/RS-422 serial ports connect serial devices, such as printers and modems, to the system.
The factory-installed IO9 card provides the following connectors:
Real-time interrupt input and output. RTO (output) enables the compute module to interrupt an external device. RTI (input) enables an external device to interrupt the compute module.
Ethernet port (10/100/1000 Mbits). This autonegotiating 10BaseT/100BaseT/1000BaseT twisted-pair Ethernet port connects the compute module to an Ethernet network.
SCSI connector. This 68-pin VHDCI external SCSI port enables you to connect SCSI devices to the compute module. For an updated list of supported SCSI devices, see the SGI Supportfolio at http://support.sgi.com .
This section lists the internal compute module configuration options, such as the number of DIMMs that can be installed in the compute module to increase its local memory.
This section also lists external compute module configuration options that can enhance the performance of the Origin 350 server system. For example, the compute module can connect to a 2U TP900 storage system to expand storage, or it can connect to a PCI expansion module to increase I/O capabilities.
Processors, PCI and PCI–X cards, disk drives, and memory (DIMMs) are the configurable internal components of the compute module.
 | Warning: Of these configurable items, processors and the IO9 PCI card, can be installed and removed only by trained SGI system support engineers (SSEs). |
As a customer, you can configure PCI and PCI-X cards, disk drives, and memory. See Chapter 4, “Installing and Removing Customer-replaceable Units,” for information about installing and removing these items to reconfigure your server module.
| Warning: To prevent personal injury or damage to your system, only trained SGI system support engineers (SSEs) can service or configure internal components of the compute module that are not specifically listed as serviceable and configurable by customers. |
The base compute module can be configured with the following optional items to expand its function:
The system expansion compute module, which is interconnected to the base compute module via a NUMAlink 3 cable, adds processors, memory, and four PCI/PCI-X card slots. It may or may not include an IO9 card. (The combination of the base compute module with the system expansion compute module can create a single system that includes 4, 6, or 8 processors, with up to 16 GB of local memory, and seven PCI/PCI–X card slots.)
The 4U PCI expansion module adds PCI slots, but no processors, no memory, and no IO9 card. There are two versions of the PCI expansion module: one module has 12 PCI slots that support 3.3-V or universal PCI cards, and the other module has 6 PCI slots that support 5-V or universal PCI cards and 6 slots that support 3.3-V or universal PCI cards. For more information about this module, see PCI Expansion Module User's Guide (5.0-V Support and/or 3.3-V Support) (007-4499-00x).
The 2U memory and PCI expansion (MPX) module can provide extra memory and four PCI/PCI-X card slots to your system. See Chapter 4, “Memory and PCI Expansion (MPX) Module” for more information about this module.
The TP900 storage module provides additional storage to the system. See SGI Total Performance 900 Storage System User's Guide, 007-4428-00x, for information about this module. The Origin 350 server system supports other storage modules. See “Storage Expansion” in Chapter 2 for information.
The NUMAlink module connects two or more compute modules. See Chapter 5, “NUMAlink Module” for more information about this module.
The Origin 350 server system can be configured in many different ways to satisfy your computing needs. This section shows two sample configurations.
Figure 3-7 shows an Origin 350 server system on a table top that includes the following items:
A 2U base compute module has 4 processors, 8 GB of local memory, and three PCI/PCI–X card slots. The fourth lowermost PCI/PCI–X slot comes with a factory-installed IO9 PCI card. (Because the IO9 card is a 66 MHz PCI card, the slot immediately above where the IO9 card is installed, which is on the same bus, can only accommodate PCI cards that will run at a speed of 66 MHz or slower.)
An MPX module adds 8 GB of local memory and four PCI/PCI–X card slots.
Figure 3-8 shows an Origin 350 server system rackmounted in a 17U rack that includes the following items (from top to bottom in the rack):
A 4U PCI expansion module adds 12 PCI card slots to the server system.
An MPX module adds 8 GB of local memory and four PCI/PCI–X card slots to your server system.
A NUMAlink module (router) interconnects all the modules together into one server system.
A 2U system expansion compute module adds 4 processors, 8 GB of local memory, and four PCI/PCI–X card slots.
A 2U base compute module adds 4 processors, 8 GB of local memory, and two PCI/PCI–X and one PCI card slots. The fourth lowermost slot comes with a factory-installed IO9 PCI card. (Because the IO9 card is a 66 MHz PCI card, the slot immediately above where the IO9 card is installed, which is on the same bus, can only accommodate PCI cards that run at a speed of 66 MHz or slower.)
A power bay.
Figure 3-8. System with a PCI Expansion Module, an MPX Module, a NUMAlink Module, a System Expansion Compute Module, and a Base Compute Module
Table 3-4 lists the bandwidth characteristics of the compute module.
Table 3-4. Bandwidth Characteristics of the Compute Module
Characteristic | Peak Bandwidth | Sustainable Bandwidth |
|---|---|---|
NUMAlink channel | 3.2 GB/s full duplex 1.6 GB/s each direction | ~1420 MB/s each direction |
Xtown2 channel | 2.4 GB/s full duplex 1.2 GB/s each direction | ~1066 MB/s half duplex ~1744 MB/s full duplex, ~872 MB/s each direction |
Main memory | 3200 MB/s | 2140 MB/s |
SYSAD | 1600 MB/s | ~1400 MB/s |
Table 3-5 summarizes the general features of the compute module.
| Note: The following table assumes that the expansion compute module does not include an optional IO9 PCI card, which would add one input and one output real-time interrupt port, an Ethernet port, and an internal and external SCSI drive, and support for one serial port. The IO9 card is also needed to support the DVD–ROM, the SCSI disc drives, and the serial daughtercard with the PS/2 connectors and three serial ports (this serial daughtercard is not an option for the expansion compute module). |
Table 3-5. General Features of the Compute Module
Feature | Base Compute Module | Expansion Compute Module |
|---|---|---|
MIPS RISC processor | 2 or 4 | 2 or 4 |
Memory | 1 GB to 8 GB | 1 GB to 8 GB |
Expansion slot | 1 PCI, 2 PCI-X | 4 PCI-X |
Console port | 1 | 1 |
NUMAlink port | 1 (1.6 GB/s each direction) | 1 (1.6 GB/s each direction) |
XIO port | 1 (800 MB/s each direction) | 1 (800 MB/s each direction) |
L1 port (USB, type B) | 1 | 1 |
Serial port | 4 |
|
PS/2 port | 1 keyboard and 1 mouse |
|
RT interrupt input port | 1 |
|
RT interrupt output port | 1 |
|
Ethernet port | One 10BaseT/100BaseT/1000BaseT |
|
SCSI port (internal) | 1 Ultra3 SCSI, 160 MB/s |
|
SCSI port (external) | 1 Ultra3 SCSI (VHDCI) |
|
3.5-in. drive bay | 2 |
|
Table 3-6 lists the specifications for the compute module.
Table 3-6. Compute Module Specifications
Characteristic | Specification |
|---|---|
Height | 3.44 in. (8.74 cm) |
Width | 17.06 in. (43.33 cm) |
Depth | 27 in. (68.58 cm) (with bezel) |
Weight | 37.80 lb (17.18 kg) minimum configuration; 44.50 lb (20.23 kg) maximum configuration[a] |
Noise | 6 Bels sound power, up to 30 ºC |
Heat dissipation | 1315 Btu/hr maximum |
Input power | 120 - 240 VAC |
[a] Weight will vary depending on whether your system has one or two power supplies, on the amount of DIMMs installed, and on whether you have one or two disk drives in your system. | |