HP d325 MT Reference manual
Configuring Graphics Memory
for HP Business Desktop d325 Microtower
Abstract.............................................................................................................................................. 2
Introduction......................................................................................................................................... 2
Graphics Memory Allocation ................................................................................................................ 3
Graphics Driver................................................................................................................................... 3
Main Memory Configuration................................................................................................................. 4
Memory Speed.................................................................................................................................... 4
Summary ............................................................................................................................................ 5
Appendix ........................................................................................................................................... 6
Example 1....................................................................................................................................... 6
Example 2....................................................................................................................................... 7
Example 3....................................................................................................................................... 8
2
Abstract
By incorporating processors, chipset and integrated graphics from AMD and NVIDIA, the HP Business
Desktop d325 delivers 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 graphics memory allocation is hidden from the
operating system and cannot be used for other purposes.
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.
Introduction
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:
•Up to 2 GB of dual-channel DDR main memory
•The latest NVIDIA nForce2 GT chipset
•Integrated NVIDIA GeForce4 MX graphics with up to 64 MB of DDR memory automatically
allocated to graphics
•Award-winning AMD Athlon 1XP processors
•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.
1For 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.
3
Graphics Memory Allocation
Up to 64MB 2of 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. The graphics memory allocation is hidden from
the operating system and cannot be used for other purposes. 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 Graphics memory allocation
Less than 256 MB 16 MB
256 MB 32 MB
384 MB or more 64 MB
Alternatively, the end-user can manually specify an allocation of up to 128 MB.
Note:
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.
2Up to128 MB if allocated manually
4
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 Description
Support PC2100, PC2700
DIMM slots Two
Channels 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.
•Dual channel—With both DIMM slots populated, the memory bus becomes128-bits wide, doubling
memory bandwidth. Memory performance can improve significantly.
Note
Performance tests carried out by HP on a d325 business desktop show the
following performance gains for dual-channel over single-channel 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 3by 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.
3To maximize system performance, the BIOS sets actual memory speed to not exceed the speed of the front-side bus.
5
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 dual-channel and part is
single-channel.
Note
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.
•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
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.
6
Appendix
This Appendix offers graphical representations of two issues that may impact performance:
•Mismatched (differently-sized) DIMMs are deployed
•An alternative graphics driver is used
Note
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.
Example 1
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.
Note
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.
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 set-up utility) to create a multi-monitor
configuration 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.
7
Example 2
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.
8
Example 3
In this example (shown in Figure 3), the end-user is deploying mismatched DIMMs. There is an
alternative graphics driver.
Note
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.
© 2004 Hewlett-Packard Development Company, L.P. The information
contained herein is subject to change without notice. The only warranties for
HP products and services are set forth in the express 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.
348600-002, 06/2004
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