Cache Memory

MegaRAID Express 500 cache memory resides in a memory bank that uses 2 M x 72 (16 MB), 4 M x 72 (32 MB), 8 M x 72 (64 MB) or 16 M x 72 (128 MB) unbuffered 3.3V SDRAM . Possible configurations are 16, 32, 64, or 128 MB. The maximum achievable memory bandwidth is 528 MB/s.

MegaRAID supports write-through or write-back caching, which can be selected for each logical drive. To improve performance in sequential disk accesses, MegaRAID does not use read-ahead caching for the current logical drive. The default setting for the read policy is Normal, meaning no read-ahead caching. You can disable read-ahead caching.

Warning!

Write caching is not recommended for the physical drives. When write cache is enabled, loss

of data can occur when power is interrupted.

MegaRAID BIOS

The BIOS resides on a 1 MB × 8 flash ROM for easy upgrade. The MegaRAID BIOS supports INT 13h calls to boot DOS without special software or device drivers. The MegaRAID BIOS provides an extensive setup utility that can be accessed by pressing <Ctrl> <M> at BIOS initialization. MegaRAID BIOS Setup is described in the MegaRAID Configuration Software Guide.

Onboard Speaker

The MegaRAID Express 500 controller has an onboard tone generator for audible warnings when system errors occur. Audible warnings can be generated through this speaker. The audible warnings are listed on page 117.

Serial Port

MegaRAID Express 500 includes a 3-pin RS232C-compatible serial port berg connector, which can connect to communications devices.

Chapter 4 Features

33