Internal storage areas, governed by a tricky tapestry of pointers and storerooms, and necessary for making software programs run smoothly.
Machine memory, mercifully, is slightly more manageable than the woolly inner workings of the human brain, which desperately tries to retain some memories, and shed others. Machines can be ordered to always remember, never forget.
An obvious example is the digital set-top box. What one hears most vociferously about them is how much memory they don’t have. But, as is usually the case in technological matters, there’s a lot more to be said about machine memory and how it works than the shrill refrain of “not enough.”
For starters, electronic memory is generally stored on chips. It is measured in kilobytes (abbreviated “kB”) and megabytes (abbreviated “MB.”) Some types of memory are more expensive than others, but in general, memory prices are falling predictably.
The digital set-tops shipping today – models on or after the “2000″ series of both Motorola and Cisco/Scientific-Atlanta – contain at least three different types of memory. In techno-speak, these three memory types go by “NV-RAM,” for “non-volatile, random access memory;” “flash;” and “DRAM” (pronounced “dee-ram.”)
Flash and DRAM memory generally get the most talk-time among digital box aficionados. Maybe you’ve heard a technologist refer to set-top memory as “four by eight,” or “one by two.” The first number is the number of megabytes of flash memory. The second number is the number of DRAM megabytes. A four-by-eight configuration, then, is a box that contains 4 Megabytes of flash memory, and 8 Megabytes of DRAM.
In general, the difference between the three types of set-top memory involves what stays in the storage cells when the power goes out. Non-volatile, in this sense, means “must stay.” Both NV-RAM and flash memory chips are configured to keep stored information when the power fails. DRAM memory cells, by contrast, are volatile: They blank out when the power goes, and need to be refreshed.
NV-RAM is the tiniest of the three, capacity-wise. It is generally sized in kilobytes per unit. NV-RAM holds super-critical stuff: The identification number of the box. Customer-generated preferences, including any parental locks. Information about pay-per-view purchases, for inclusion in the next monthly bill.
NV-RAM is much like the first data you learned as a child, and the first data you teach your children to remember: Name, address, telephone number.
Flash is the most expensive of the three. A sort of re-writeable NV-RAM, flash memory used in contemporary digital set-tops is sized in the low Megabytes – from 1 MB to 4 MB, in the baseline cases of most set-top makers.
Flash memory holds the software code that makes various applications work – the “applications code,” or “executables,” in technical parlance. This means the operating system, the program that evokes the electronic program guide, and any other “resident applications” present in the box.
Flash, in human terms, holds the things you tend to remember no matter what: Your birthday. The Pledge of Allegiance. Multiplication tables. How to tie your shoe. The words to your favorite songs. Things you hold dear, either by repetition or vigilance.
DRAM holds the information used by the applications held in flash – the “apps data,” in tech-speak. DRAM is volatile, meaning that if the power fails, all its storage cells are emptied. Guide data is a good example: When the power returns to the box, all of the titles and descriptions of TV shows must be re-loaded. In some cases, applications code, like the software files that make VOD work, are loaded into DRAM, and initiated when a digital customer evokes the application.
The constant in machine memory is this: No matter how cheap it gets, and no matter how much of it snaps into electronics devices like the digital set-top, there will never, ever be enough. Such is the nature of software: Like a gas, it tends to fill all available space.