Agilent Technologies 75000 SERIES B, E1301B Memory Configuration, Positioning of Allocatable RAM

Memory Configuration

NOTE

Before attempting to download any device drivers you should understand how memory is affected when you specify a size for one or more types of RAM. There are three types of RAM that you can allocate in the mainframe:

•RAM disk (RDISK)

•Non-volatile RAM (NRAM)

•Driver RAM (DRAM)

Figure 5-2 shows the positioning of these areas in memory. User Non-volatile RAM and RAM Disk both occupy higher memory addresses than the Driver RAM. Because the actual size of these three areas is variable, they do not have a fixed starting position. At creation time, the lowest unused memory address becomes the starting address for the requested type of RAM. Memory areas set at higher addresses can be created without affecting any previously created lower memory areas, but creating a new memory area causes any areas above it to be removed.

If you wish to use RDISK or NRAM, you can modify the configuration file so that the download program sets up the required memory segments.

FFFFFFh

Low Memory

System Non-volatile

Instrument Memory

Operating System memory

RAM Disk

Non-volatile User RAM

Driver RAM

The Low Address depends on the amount of memory installed. It is equal to the highest address plus 1 (1000000h) minus the size of memory installed. The boot time messages will tell you how much RAM you have installed in your system. In a system with 512Kbytes of memory the Low Address is low address = 1000000h - 80000h = F80000h, or 16,252,928 decimal.

Figure 5-2. Positioning of Allocatable RAM

Example If you create a RAM Disk area without creating any User Non-volatile RAM or Driver RAM, the starting address for the RAM Disk will be at the lowest address (F80000h for a command module with 512Kbytes of memory). If you now create a Driver RAM area, the RAM Disk area will be removed since the new area has to be at a lower address then the RAM Disk area.

Downloading Device Drivers 5-3