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T e c h n i c a l I n f o r m a t i o n
Memory
Server memory is located on one or two ECC memory module expansion
cards. Fully loaded, one card provides 384 Mbytes of common high-
speed memory for the server. The card has three memory banks. Each
bank consists of four SIMM sockets. Each socket can hold a 2, 4, 8, 16,
or 32 Mbytes approved fast-page parity SIMM. You can install any size
SIMM in any bank; however, all four SIMMs within a bank must be the
same size (see Chapter 3, Upgrading Your System, for more information
about SIMMs). The SIMM's height must not exceed one inch; taller
SIMMs will interfere with an adjacent CPU card or ECC memory card. If
you need more memory, you can install an additional ECC memory card
in the server. Fully loaded, the two cards provide 768 Mbytes of common
high-speed memory for the server.
The ECC memory card detects and corrects single-bit errors from DRAM
(Dynamic Random Access Memory) in real time, allowing your system to
function normally. It detects all double-bit errors but does not correct
them; it also detects all three-bit and four-bit adjacent errors in a DRAM
nibble but does not correct them. When one of these multiple-bit errors
occurs, the ECC memory card generates an NMI (NonMaskable Interrupt)
and usually halts the system.
The data transfer width of the ECC memory card is 64/128 bits. It is
compatible with all Pentium processor modules.
The server supports both base (conventional) and extended memory. Base
memory is located at addresses 00000h to 9FFFFh (the first 640 Kbytes).
Extended memory begins at address 100000h (1 Mbyte) and extends to
the limit of addressable memory (4 Gbytes).
Some operating systems and application programs use base memory; for
example, MS-DOS, OS/2, and UNIX. Other operating systems use both
conventional and extended memory; for example, OS/2 and UNIX. MS-
DOS does not use extended memory; however, some MS-DOS utility
programs such as RAM disks, disk caches, print spoolers, and windowing
environments use extended memory for better performance.
5-4 OWNER'S HANDBOOK
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