|
BOOT CAMP 191 (06/09/01)
MEMORY CARDS, part 1
If you haven't yet got a digital still camera (DSC) it's
probably only a matter of time before you do and when that happens it can be
helpful to know a little about memory cards. They're the digital camera
equivalent of photographic film and are used to temporarily store images, before
they are copied across to a PC or printed out. This week we'll look at the
various types of card in use at the moment, next week the practicalities of
using them, how to get the data in and out and how to manage the files they
contain.
The memory cards used in DSCs are distantly related to the
RAM (random access memory) modules in your PC in that they are rewritable and
they store large volumes of digital data. However unlike RAM modules, memory
cards are 'non-volatile', which means that the information they contain is
retained when the device is switched off and the card is removed from its holder
or 'slot'. This type of storage is also sometimes known as 'Flash' memory
Non-volatile memory is used in a wide variety of
applications, from the personal 'phone books' on SIM (subscriber identity
module) cards used in mobile phones to storing user data on digital television
viewing cards and 'keycards' to open doors and access secure areas in offices
and buildings.
Memory cards come in a wide range of shapes and sizes but at
the moment only four types are used consumer products like digital cameras and a
range of other portable devices, such as MP3 personal stereos, digital
camcorders, portable and handheld computers and pocket organisers.
The first and currently most popular type of memory card is
the Compact Flash (CF) card. CF cards are roughly the size of a small box of
matches and about twice the thickness of a credit card (43 x 36 x 3.3mm). Cards
with a capacity of up to 640 megabytes (640Mb) have recently become available
with the possibility of even higher capacities in the future. Unlike most other
types of memory module CF cards contain a disc controller chip to speed up
operation and make them compatible with any PC (with a suitable slot or
adaptor), which immediately recognises the card and treats it as an extra disc
drive. Two years ago a new variant of the CF specification was introduced,
called Type II. This allows for a slightly thicker card slot that's compatible
with the original Type I cards, but enables other devices to be used as well,
like the IBM MicroDrive (up to 1Gb) plus thicker and eventually even higher
capacity Type II CF cards. Compact Flash cards operate on two voltage standards
(3.3 and 5 volts), though this doesn't appear to have any compatibility
implications and both types of card are interchangeable. Thanks to the built-in
controller chip data transfer rates on CF cards – i.e. the speed at which data
can be written to the card – is fast, and getting faster all the time and for
that reason they are often used on high-end and professional digital
cameras.
The smallest memory card is the postage-stamp sized
Multimedia Card or MMCs; they're also light and slightly thicker than a credit
card (24 x 32 x 1.4mm). Memory capacities range from 2 to 64 megabytes. Until
fairly recently that was considered to be more than adequate for most
applications, however as with all things digital, storage requirements escalate
and last year a consortium of companies, led by Matsushita, Toshiba and Sandisk
introduced a new variant on the MMC card called the SD (Secure Data) card. The
SD card is slightly thicker than a regular MMC (2.1mm), it has a
write-protection switch on the side, built-in anti-piracy copy protection called
SDMI (Secure Digital Music Initiative) and greatly increased memory capacities
which currently extends up to 256Mb. Devices that use SD cards can also read and
write data to MMC cards, though it doesn't always work the other way around and
older devices that use MMC cards won't necessarily be compatible with higher
capacity SD cards.
SmartMedia (SM) cards are popular on mid-market digital still
cameras due to their convenient size, simplicity and relative cheapness. The
cards are slightly smaller than a book of matches and thinner than most credit
cards (45 x 37 x 0.76mm). SmartMedia cards are pure memory, nothing else and
megabyte for megabyte they tend to be a little cheaper than the other formats.
SmartMedia cards can be easily read on PCs with PCMCIA card slots, using a
simple adaptor (more about that next month) and they are very robust. The only
downside is that memory capacity is lagging some way behind rival cards and
128Mb modules have only recently become available, moreover there are some
compatibility issues with higher capacity cards and some older cameras.
Until just a few weeks ago Memory Stick was a proprietary
memory card technology developed and used more or less exclusively by Sony but
now there are signs that the chewing gum sized modules (21.5 x 50 x 2.8mm) are
gaining wider acceptance with news that Samsung will also be using them in its
products. Memory stick is the most recent arrival and was first introduced in
1999. Capacities of 128Mb are on sale now and Sony confidently predicts that 1Gb
Sticks will be developed in the near future. There are two types of Memory
Stick, the standard module is coloured purple and will work in all devices
except MP3 players. The second type, labelled MagicGate, is coloured white and
allows copyright material to be copied so it works in all products including MP3
players. Thanks to Sony's decision to integrate Memory Stick technology across
its product range (DSCs, digital camcorders, laptops, MP3 players, etc.), it has
quickly become established moreover now that other manufacturers have adopted it
and prices are coming into line with other types of memory card its future seems
assured.
Next week – memory cards, part 2
JARGON FILTER
DISC CONTROLLER
Microchip that identifies a disc drive or storage device to a
computer and helps speed up the transfer of data
PCMCIA
Personal Computer Memory Card International Association. Body
responsible for PC card standards. PC cards are credit card sized modules (but a
little thicker) used in laptops for modems, memory expansion and other
peripherals
WRITE PROTECTION SWITCH
Mechanical device – usually a simple slide switch – that
indicates that the data on the card is protected and cannot be over-written
TOP TIP
A few weeks ago in Boot Camp we spoke about adding an extra
cooling fan to stop your PC overheating in the hot weather, but how can you tell
if your computer is suffering? It just so happens that many recent PC
motherboards have built in temperature sensors that keep a running check on
vital components. Motherboard Monitor (v5) is a neat freeware utility that puts
that information on the screen, so you can see for yourself what's going on. Not
all motherboards are supported, but the program will check your PC for
compatibility before it runs. The file is 1.5Mb and it can be downloaded from:
http://mbm.livewiredev.com/
|
