HP X Class 500/550MHz, Reference Manual

Page: 49 / 149

Chapter 2 49
System Board
Main Memory Bus
Main Memory Bus
The memory bus is 72-bits wide, comprised of 64 bits of data and address information, and
8 bits of Error Correcting Code (ECC). The bus is connected to the Main Memory and to
the Host Bridge (Intel 440GX) chip.
HP V
ISUALIZE
Personal Workstation models are supplied with a 128 MB unbuffered ECC
SDRAM memory module in one of the four DIMM slots, leaving the other slots free for
memory upgrades. If additional memory is required, up to 1 GB (4 x 256 MB) of unbuffered
memory may be installed. Memory upgrades are available in single 64 MB, 128 MB or 256
MB unbuffered ECC SDRAM modules.
Or, alternatively, the existing unbuffered memory modules may be replaced by Registered
ECC SDRAM memory modules. Memory can be upgraded to a maximum of 2 GB using
multiples of 512 MB Registered or unbuffered ECC SDRAM memory modules (4 x 512
MB). Both the 512 MB Registered and unbuffered memory modules were not available at
the time of introduction of the HP V
ISUALIZE
Personal Workstations
NOTE Unbuffered and Registered ECC memory modules are not compatible with
each other, and cannot be mixed.
Refer to the section “DIMM Sockets” in this chapter for information about the DIMM
sockets.