Memory

MEMORY Intel’s 80386, 80486, and Pentium microprocessors are 32-bit processors, which means that

they can manipulate binary numbers as large as 11111111111111111111111111111111, which

translates to the decimal number 4,294,967,296, or 4GB (gigabytes).

The memory management features of Windows use real and virtual memory to let you open

multiple applications at the same time, even if there isn’t enough physical memory to open them

all. With the improved memory management of Windows 95 and Windows 98, you can run more

applications before getting the out-of-memory message than you could in Windows 3.1.

All 16-bit (Windows 3.1) applications run together in a single memory space above the 32-bit applications. Although each application occupies its own piece of memory at one time, it may have to give up the use of a portion of RAM for use by an-other 16-bit application in a procedure called cooperative multitasking. When applications don’t cooperate properly, a system crash can occur.

If there isn’t enough unallocated mem-ory to match the application’s request, Windows uses virtual memory—hard disk space—to store RAM code that has not been re-cently used. Windows 95 can automatically vary the amount of disk space required for virtual memory. If the program whose memory was swapped to disk needs that data or code back, Windows will allocate real RAM for it, and swap another application’s memory to disk. If any ap-plication (16- or 32-bit) needs additional memory space, it sends a request to Windows, which checks to see how much memory is available. Windows then assigns an additional free stretch of memory to that application.

Dram vs. Sram: Static Ram is much faster the Dram, 25ns compared to 60- 80ns typically and is therefore is much more expensive. Putting this into perspective, a nanosecond (ns) measures transfer speed of a billionth of a second. Static ram is most commonly used for caching, and Dynamic Ram is what we talk about when we usually talk about Ram.