BCM Advanced Research
12
Memory Subsystem
The IN440EX DRAM controller supports a 64-bit memory data interface, optionally supporting 64-bit wide DIMM
modules, without ECC/EC. The DRAM types supported are Synchronous DRAM (SDRAM). SDRAM is supported at
66 MHz using symmetrical addressing.
The IN440EX Main Memory interface provides two (2) 168-pin DIMM socket (DIMM0 and DIMM1) sites, allowing
system memory from 8MB to 256MB of SDRAM.
The DIMM sockets support either single or double-sided
‘Unbuffered DIMM’
modules. The installed DRAM type
can be 8MB, 16MB, 32MB, 64MB or 128MB DIMMs. The DRAM Controller uses the JEDEC standard Serial
Presence Detect (SPD) Mechanism to detect memory and array configurations, there is no jumper settings required for
the memory size. Memory is automatically detected by the system BIOS.
Rules for Populating the DIMM memory array
•
DIMM sockets can be populated in any order.
•
The DRAM Timing register, which provides the DRAM speed grade control for the entire
memory array, will be programmed to use the timings of the slowest DRAMs installed.
Data Integrity Subsystem
Several data integrity features are included in the system. These are 64-bit DRAM interface for EX chipset,
parity generation and checking on the PCI Bus and A.G.P. (for PCI transactions).
PCI Bus.
The system implements parity generation/checking as defined by the PCI specification.
A.G.P. Bus.
For the operations on the A.G.P. interface using PCI protocol, the system supports Parity generation/checking as
defined by the PCI specification.
Main Memory DRAM Protection Modes.
The system supports three modes of data protection of the DRAM array:
•
Non-ECC with Byte-Wise Write Support (Default mode, in this mode there is no provision for
protecting the integrity of data in the DRAM array.)
A.G.P. Interface
The A.G.P. is a high performance, component level interconnect targeted at 3D graphics applications and is based
on a set of performance enhancements to PCI. The IN440EX is designed to support the A.G.P. Interface.
The A.G.P. implementation is compatible with the Accelerated Graphics Port Specification. The system supports
only a synchronous A.G.P. interface coupling to the host bus frequency. The actual bandwidth will be limited by
the capability of the system’s memory, reaching the highest performance with fast SDRAM. The A.G.P. Interface
supports PCI operations as defined by the PCI specification. Electrically, only 66MHz PCI operations are
supported.
