MaximumPC 2004 03

RAM

TECHNOLOGY

TYPES CLOCK

SPEED

FORM

FACTOR

MAXIMUM

THROUGHPUT

NOTES

SDRAM DIMM

PC66 66MHz 168-pin 533MB/sec One access per

clock cycle

PC100 100MHz 800MB/sec

PC133 133MHz 1.066GB/sec

DDR SDRAM

DIMM

PC2100 100MHz 184-pin 2.1GB/sec Two accesses

per clock cycle

PC2700 133MHz 2.7GB/sec

PC3200 166MHz 3.2GB/sec

PC3700 200MHz 3.7GB/sec

PC4000 250MHz 4.0GB/sec

RDRAM RIMM

RIMM1600 400MHz 184-pin 1.6GB/sec 16-bit (single

channel)

RIMM2100 533MHz 2.1GB/sec

RIMM2400 600MHz 2.4GB/sec

RIMM3200 400MHz 242-pin 3.2GB/sec 3 2-bit (dual-

channel)

RIMM4200 533MHz 4.2GB/sec

RIMM4800 600MHz 4.8GB/sec

RAM STATS

Your basic run-of-the-mill RAM test pro-

gram writes various test patterns into

memory and reads them back again; if the

patterns don’t match, you have bad memory.

The process can take anywhere from a few

minutes to several hours.

The best way to test memory, however,

is with a hardware tester. We like the

R.S.T Pro2 (RAM Stress Test) card made by

Ultra-X (www.uxd.com). It plugs into a PCI

slot, tests virtually every type of memory

while installed in the computer, and works

with the latest processors and chipsets.

We used it for our “Memory Meltdown

Challenge” in the November 2003 issue.

Hardware testers cost serious bucks.

Fortunately, there are several free test-

ing programs available which can

help you detect some problems with

memory. Our favorite is Memtest 86 , avail-

able from http://www.memtest86.com. You

can also download Doc Memory from

http://www.simmtester.com. Both programs are

available on this month’s Maximum CD.

Other memory test programs are included

in diagnostic programs.

How We Test RAM

MARCH 2004 MAXIMUMPC 55

Figure 5: DDR2 memory, like the one shown

above, can scale up to 800MHz while running

the memory core at just one quarter of that

speed, a more efficient design that cuts its power

requirements in half compared with DDR.

you will be able to buy systems
that use the next generation
of DDR memory, DDR2. DDR2,
previously known as DDR-II, is
designed to solve the shortcom-
ings of current DDR memory:

 Power: DDR2 uses less than
half the power of DDR memory
to help reduce heat buildup
and demands on laptop battery
power.

 High clock speeds: DDR2
starts at 400MHz effective clock
speed and can scale to 800MHz
while running the chip core at
just a quarter of the effective
clock speed.

 Component density: DDR2
supports up to 2Gb chips,
enabling a 2GB module to be
supplied as a single-sided mod-
ule.

 Chip size: DDR2 memory
chips are half the size of those
used by DDR modules.

 Chip connection technology:
DDR2 memory chips use a ball
grid array (BGA) connector.

Figure 4 (page 54) compares
the speeds used in a PC133
(133MHz) SDRAM module, a
current DDR PC3200 (400MHz)
module, and a DDR2 400MHz
module. Note that both the DDR
and DDR2 modules have the
same effective clock speed, but
the DDR2 module does it with
memory at a slower core rate
than the old PC133 module!
Externally, a DDR2 module
(Figure 5) resembles a DDR
DIMM. However, note the small-
er size of the memory chips
and the 240-pin connector. SO-
DIMMs for notebooks use a 200-
pin connector, and mini-DIMMs
made for specialized uses such
as printers and routers use a
244-pin connector. n