Random Access Memories; that is, not everything you show yourself first…

Everything you need to know about RAM, ROM.

Random Access Memories; that is, not everything you show yourself first…

RAM, ROM abbreviations are not new to those who are a little familiar with computer science (although it is like driving with a license, quasi-competent), yet, let's start with them first. Both are of English origin, ROM, or Read-Only Memory, is still relatively obvious. RAM, ie Random Access Memory, is less, since translated into Hungarian it would mean Random Access Memory, but not because it is where it is, where it is not…

If we imagine an A4 checkered sheet in front of us, in which we can store a number in each cube, we can also get directly to the number in the middle of the sheet, without having to start reading from the top of the sheet. So let's call RAM Rather Memory Access. Unlike ROM, RAM is also writable and readable.
Self-appointed computer technicians tend to shuffle the hard drive here as a type of memory because “the machine will slow down if I copy a lot of things,” but that’s the wrong approach. The hard drive is a storage device that works on a completely different principle, plus it is not used in a PDA (there have been embarrassing attempts). So the point for us is: RAM is a fast read / write, while ROM is a fast read-only memory device. (The author talks too much.)

The PDA has both RAM and ROM type modules and is integrated into the device's motherboard. According to their internal structure, they mostly belong to the family of EEPROMs (electronically rewritable memories). "Non-volatile solid state flash memories", ie circuit elements which do not contain moving parts, the contents of which can be changed by current (ROM only with special external devices, see "flash") and which retain the information written to them after a power failure .

It’s a big blessing, a few years ago they weren’t cheap enough for mass production, so manufacturers used chips that could only keep data discharged using an external power source (a tiny button cell). If this was removed or the battery was depleted, only the backup helped.

In terms of usage speed, flash memory chips are almost as fast as DRAMs, which provide the RAM for PCs and forget about the information entered after being turned off, i.e., volatile.

The amount of data that can be stored in memories can be expressed in the usual units of measurement (megabytes, kilobytes) used in computer technology. In general, the higher this value, the greater our room for maneuver.

ROM, which cannot be modified by the user, is loaded with content by the manufacturer, including the operating system (Windows, Android, etc.) and pre-installed programs (eg factory games, browsers, mail client utilities).

Unlike PCs, RAM is logically divided into two parts. It is reserved by the system and user or storage memory (for Windows users this is My Storage). In the latter part we can freely copy data, music, pictures, install our own programs, our e-mail client and other messages (sms, mms) can be placed here, while the part reserved by the system is a cache, a kind of desktop of the system, where the currently running programs and the temporary data they generate, open files, and are deleted after the program is closed.

The latter small part is therefore in a constantly changing state, but its size is limited, so it is conceivable that, for example, while listening to music, you do not completely upload the currently playing mp3 file to this operating area, but only play a small part of it. the next part of the file, etc., so there is room for other tasks.

On older devices (such as the Acer N50), the allocation of internal RAM could be controlled from the Control Panel, so it was up to the user to decide how much internal memory to use for storage and how much to run programs. Sounds good? The reason this is no longer the case is that we can parse memories in other ways, and this is true for both ROM and RAM: there is NAND and NOR type memory, the name for how their cells are connected refers to (serial or parallel).

In general, NOR (RAM / ROM) memories are faster to read and write, while NAND (ROM / RAM) memories are the other way around, and NAND memories only allow serial reads, while NOR memories allow random block reads. . In addition, NOR allows XIP, i.e., “starting locally,” so you don’t have to upload and run individual programs, but you can work with them locally. It is important to know that XIP only applies to programs, there is no data, they must be copied to the operational part before use. A small detail is hidden here: less copying means less power consumption and program startup is also faster. An ideal system would be close to 50-50% in terms of NAND and NOR, unless there is something else here.

In addition to NAND and OneNAND, which are not discussed in more detail, the internal memory interface is able to connect high-speed DRAMs, which can be mobile DDR or SDRAM, operated at low voltage and temperature-controlled, from which the previously mentioned “operational desktop” can be built. ”.

The question may arise: are these not having trouble with a lot of writing and reading?

Well, like all electrical devices, of course, they have a life cycle, which they try to eliminate in everyday use with various techniques, so as they regularly check the integrity of the data with a separate circuit and mark the memory compartments that are considered faulty, and the system avoids their use. User-accessible storage memories typically use the FAT32 / EXT3 file system to store files. This is a kind of compromise because both have been designed for magnetic hard drives, with endless write capability, but in other respects they fit perfectly. In general, as long as a PDA doesn’t go deep into the drawer when the offspring arrive, it can withstand the memory, but it’s better to be careful and save your data from time to time.

If anyone gets this far, they’ve really been pretty determined on the subject already, so I’ll quote him that the answer is that the Meaning of Life is 42, so the question for that originally was how much 6 multiplied by 7. Let's move on.

Finally, there is another group of flash memories that we use (not only) in PDAs. SecureDigital cards, commonly referred to as “escard cards”. This is the only way to increase our storage capacity, they are available today in different storage sizes (2-4-8-16-32 GB). Sizes larger than 4GB operate according to a faster SDHC standard (we need an SDHC-capable card reader to read the latter) and are classified based on quasi-speed (Class 2,4,6,10), where the number indicates a transfer rate of MB / s . The SDXC standard has also been released, which supports storage up to 2 terabytes in size.

Based on its internal structure, SD cards are NAND, i.e. non-volatile memories, so it is not particularly worthwhile to use anything other than data storage. Of course, there is a fault-tolerant and corrective system in these as well. Older devices prefer the SD / MMC card, today's ones prefer the micro SD card.
 
Although we were only able to review a slice of the topic with the article, overall we can see that the world of memories has evolved a lot in a few years and created tiny miracles with their help that we can now hold in our hands. The process didn’t stop, one day maybe we’ll smile and remember we once had a PDA and had a huh, 512MB of memory in it. Altogether.