HP Business PCs Desktops August 2003 How To White Paper. Configuring Graphics Memory for HP Business Desktop d325 Microtower Contents Abstract... 2 Introduction... 2 Graphics Memory Allocation... 3 Graphics Driver... 3 Main Memory Configuration... 3 Memory Speed... 4 Summary... 5 Appendix... 5 Copyright and Trademarks... 7 1
Abstract Introduction By incorporating processors, chipset and integrated graphics from industry leaders AMD and NVIDIA, the HP Business Desktop d325 delivers the latest, proven technologies at an extremely competitive price. The NVIDIA GeForce4 MX graphics integrated into the d325 business desktop can deliver a new level of high-performance graphics to the mainstream PC user. With its powerful nview multi-display architecture, Lightspeed Memory Architecture II and Accuview Antialiasing engine, the GeForce4 MX series delivers feature-rich, leading-edge graphics technology, performance and flexibility. Because the integrated graphics receive an allocation of DDR main memory, graphics performance can be tied directly to main memory performance. The d325 business desktop supports single-channel and dual-channel main memory configurations. Performance tests carried out by HP indicate that a dual-channel memory configuration can lead to significant performance gains. This white paper outlines main memory configuration issues and the performance testing, and offers recommendations for optimizing the memory configuration. The HP Business Desktop d325 is the second AMD-based business desktop from HP, further broadening the range of HP business desktops available to the customer. By incorporating processors, chip set and integrated graphics from industry leaders AMD and NVIDIA, the d325 business desktop delivers the latest, proven technologies at an extremely competitive price. The powerful d325 offers excellent value to small to medium businesses and the public sector. Key d325 features include: The latest NVIDIA nforce2 GT chipset Integrated NVIDIA GeForce4 MX graphics with up to 64 MB of automatically allocated DDR graphics memory Award-winning AMD Athlon 1 XP processors Up to 2 GB of dual-channel DDR main memory Dual-monitor support with two standard VGA monitor connections Simple, yet powerful and reliable, the d325 business desktop is an excellent investment for today s business customers. 1 For example, PC World magazine named AMD Athlon the Computer Product of the Year (June 3, 2002) for delivering today s most compelling blend of value and performance. 2
Graphics Memory Allocation Up to 64MB 2 of graphics memory part of the main memory space is available to the NVIDIA GeForce4 MX graphics integrated into the d325 business desktop. Graphics performance depends, in part, on the characteristics of that memory allocation, configuration and speed. The graphics memory allocation is made at boot time. By default, the Auto feature of the F10 set-up utility selects an appropriate graphics memory allocation based on the amount of main memory available. Table 1 shows the amount of memory allocated by the Auto feature. Table 1. Auto graphics memory allocation Main memory Less than 256 MB Graphics memory allocation 16 MB 256 MB 32 MB 384 MB or more 64 MB Alternatively, the end-user can specify a manual allocation of up to 128 MB. If the end-user specifies a graphics memory allocation that exceeds available main memory, the BIOS defaults to the Auto setting. HP recommends using the Auto feature. Graphics Driver Not only is graphics memory size important, so is location. With the HP graphics driver installed, graphics memory is allocated at the top of main memory space. If any other driver is used, graphics memory may be allocated elsewhere, potentially impacting the performance of the entire system. See the Appendix for more information. The graphics memory allocation is hidden from the operating system and cannot be used for other purposes. Main Memory Configuration Graphics performance depends, in part, on memory configuration. Main memory offers the end-user a number of configuration options, as shown in Table 2. Table 2. Auto graphics memory allocation Characteristic Support DIMM slots Channels Description PC2100, PC2700 Two Single (one DIMM deployed), dual (two DIMMs deployed) As shown in Table 2, the system board of the d325 business desktop includes two DIMM slots, each delivering an independent, 64-bit-wide memory channel. Configuring these channels appropriately can impact graphics performance. Single channel With one DIMM slot populated, the memory bus is 64-bits wide. Memory bandwidth is significantly less than that of the processor s front-side bus; the processor often wastes valuable CPU cycles waiting for access to memory. 2 Up to128 MB if allocated manually 3
Dual channel With both DIMM slots populated, the memory bus becomes128- bits wide, doubling memory bandwidth. Memory performance can improve significantly. Performance tests carried out by HP on a d325 business desktop show the following performance gains for dual-channel over singlechannel memory: SYSmark test suites, 5.6% -- 7.6%; Winstone test suites, 0.4% -- 2.9%; Mad Onion 3DMark, as much as 65%. These test results only serve as a reference to demonstrate differences that may exist between memory configurations. The results may vary with system configuration and driver versions. Memory Speed Graphics performance depends, in part, on memory speed. For convenience, the d325 business desktop supports two DDR memory standards: PC2100 266 MHz PC2700 333 MHz However, actual memory speed is constrained 3 by the speed of the processor s front-side bus. For some Athlon XP processors the front-side bus speed is 266 MHz no performance advantage is gained by using faster PC2700 memory with these processors. However, other processors, such as the XP2800+ and XP3000+, have front-side buses that operate at 333 MHz and can take advantage of the higher performance of PC2700 memory. The d325 business desktop will not support future Athlon XP processors with front-side buses that operate at a 400 MHz. HP offers the following recommendations for maximizing performance: Dual-channel While it is possible to configure single-channel main memory, HP recommends the dual-channel configuration, which doubles memory bandwidth. Matching DIMMs When configuring dual-channel memory, HP strongly recommends using DIMMs that are matched in size and speed. If DIMM speeds are mismatched, memory runs at the speed of the slower DIMM. If the DIMMs are different sizes, then part of the memory configuration is dualchannel and part is single-channel. See the Appendix for more information on the impact of using mismatched DIMMs. Memory size Depending on configuration, memory performance can differ between desktops with the same total memory size. For example, a desktop with two 128MB DIMMs may out-perform a system with a single 256MB DIMM (because the dual-channel configuration doubles memory bandwidth). Again, HP recommends the dual-channel configuration. 3 To maximize system performance, the BIOS sets actual memory speed to not exceed the speed of the front-side bus. 4
Graphics driver HP recommends using the graphics driver supplied with the d325 business desktop. Using an alternative driver may impact system performance (as shown in the Appendix). Summary Appendix The NVIDIA GeForce4 MX graphics integrated into the d325 business desktop automatically receive an allocation of up to 64 MB of DDR main memory. The d325 business desktop supports single-channel and dual-channel configurations. Performance tests carried out by HP indicate that a dual-channel memory configuration can achieve significant performance gains. Some care is required when configuring memory; mismatched DIMMs or the use of an alternative graphics driver can degrade graphics or system performance. Simple, yet powerful and reliable, the d325 business desktop is an excellent investment for today s small to medium business customers. This Appendix offers graphical representations of two issues that may impact performance: Mismatched (differently-sized) DIMMs are deployed An alternative graphics driver is used Example 1 In this context, a graphics driver supplied with the system or downloaded from the HP website is an HP driver; any other graphics driver is an alternative driver. In this example (shown in Figure 1), the end-user is deploying matched DIMMs. The graphics driver can be HP-or an alternative. Figure 1: Dual-channel memory with matched DIMMS The BIOS maps the entire memory space to be 128 bits wide. The BIOS maps the specified graphics memory allocation to the top of the memory space. Since memory is 128 bits wide, graphics performance is optimal. 5
If the end-user deploys an add-in AGP graphics card, the integrated graphics are automatically disabled; the graphics memory allocation becomes available to other applications. Example 2 If the end-user deploys a PCI graphics card, the integrated graphics are likewise disabled and the graphics memory allocation becomes available to other applications. However, if desired, the end-user can re-enable the integrated graphics (using the F10 setup utility) to create a multi-monitor configuration 4 using one or both integrated VGA ports and the PCI card s VGA port. With integrated graphics re-enabled, the BIOS maps the specified graphics memory allocation to the top of the memory space. In this example (shown in Figure 2), the end-user is deploying mismatched DIMMs. There is an HP graphics driver. Figure 2: Dual-channel memory with mismatched DIMMS, HP graphics driver The BIOS maps upper memory to be 64 bits wide, lower memory to be 128 bits wide. The BIOS maps the specified graphics memory allocation to the top of the memory space (the larger DIMM). Since upper memory is 64 bits wide, graphics performance is sub-optimal. 6
Example 3 In this example (shown in Figure 3), the end-user is deploying mismatched DIMMs. There is an alternative graphics driver. An alternative graphics driver may behave differently than an HP driver if memory is mismatched, as in this example. Figure 3: Dual-channel memory with mismatched DIMMS, alternative graphics driver The BIOS maps upper memory to be 64 bits wide, lower memory to be 128 bits wide. The BIOS maps the specified graphics memory allocation to the top of the memory space (part of the larger DIMM). The allocation is 64 bits wide. An alternative driver may automatically re-map the graphics allocation to the faster 128- bit memory space to optimize graphics performance. However, the space originally allocated by the BIOS for integrated graphics is still hidden from the operating system and cannot be used, reducing the amount of memory available for other applications. In addition, boot time may increase substantially as data from upper memory are copied to the 128-bit space. Copyright and Trademarks Copyright 2003 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice and is provided as is without warranty of any kind. The warranties for HP products and services are set forth in the express limited warranty statements accompanying such products and services. Nothing herein should be construed as constituting an additional warranty. HP shall not be liable for technical or editorial errors or omissions contained herein. August 2003 348600-001 7