MaximumPC 2004 03

4 MAXIMUMPC MARCH 2004

Beyond PC3200—

memory that works

for overclocking

The JEDEC Solid State Technology

Association ( http://www.jedec.org ) is the orga-

nization responsible for establishing

memory standards. The fastest DDR

SDRAM memory approved by JEDEC

is DDR400, which is the memory used

in PC3200 memory modules. However,

many vendors, including Corsair Memory,

Kingston, Mushkin, OCZ, and GeIL now

offer PC3700 and PC4000 modules. These

modules are designed and priced for

the overclocker/gamer market. Most of

them feature heat spreaders and other

extras designed to handle the higher

heat and voltages used in overclocking.

If you’re content to run your memory at

stock clock speeds and timings, stay with

standard modules and spend your money

elsewhere. But if the highest clock speeds

on the planet are what you’re aiming for,

PC3700 and PC4000 memory should be

on your shopping list.

As memory speeds increase, standard

timing settings become more relaxed.

For example, instead of the 2-3-2-6 tim-

ings typically used with PC3200 memory,

PC3700 and PC4000 memory often use

timings of 3-4-4-8.

Registered

memory

and the

Athlon 64 FX

To provide maximum

reliability, servers and

workstations typically use registered

DIMMs instead of the unbuffered DIMMs

used in desktop computers. A registered

DIMM uses an additional chip mounted

horizontally on the DIMM to boost

memory signals running to and from

the module. This process takes one clock

cycle, so registered memory is slightly

slower than normal unbuffered memory.

Registered memory is also more expen-

sive than unbuffered memory, cannot

be mixed with unbuffered memory, and

must be supported by the motherboard

chipset.

Because servers (which typically use

special processors such as the Intel Xeon

or AMD Opteron) use registered mem-

ory, we were surprised to learn that the

first motherboards for the AMD Athlon

64 FX also require registered memory.

Here’s why: The initial versions of the

Athlon 64 FX are based on the Opteron

server/workstation chip. It’s likely that

future versions of the Athlon 64 FX will

not require registered memory.

DDR2: The next wave

Starting late this year or in early 2005,

Figure 4: This chart illustrates how clock speed and

simultaneous memory operations per clock cycle affect

performance. Each rise and fall of the alternating

line represents a single clock cycle, and the arrows

emerging from the memory core represent how many

operations can be performed within each clock cycle.

More operations per second translates into faster

performance, while faster clock cycles allows the

memory to do more in less time.

Got questions? We got answers.

What is registered memory?

Registered memory redrives

memory signals for better reli-

ability; it can’t be mixed with

standard memory.

What is ECC? Memory that uses

additional bits for error correc-

tion; ECC support in the chipset is

required.

What is access time?

That’s the amount of time from

when a memory module receives

a request for data to the time that

data becomes available.

What is non-parity?

Memory without error-

checking or error correction.

Same as non-ECC.

Whatever happened to

quad-band memory?

The release of Kentron’s quad-

band memory (QBM), which is

designed to provide DDR2 levels

of performance in existing memo-

ry sockets by using a switching

chip plus two banks of DDR mem-

ory, is running very late. Promised

for the second half of 2003, it is

not supported by any current

chipsets; VIA’s PT880 was sup-

posed to support it, but doesn’t.

The latest news on Kenton’s

own QBM News web site

(www.quadbandmemory.com/

news/news.htm) is dated May

2003, so our prognosis for this

DDR2 alternative isn’t promising.

RAM:

All Questions Answered!

RAM FAQ