| Summary: |
DDR400: Presentation of the Module
As we already presumed the DDR400 module is built with Kingmax TinyBGA
chips, which is still the hobbyhorse of Kingmax Semiconductor. The module
comes on a completely redesigned PCB (Printed Circuit Board) which, in
order to accept future large capacity chips, has gained in profile compared
to previous PCB versions. This PCB also equips the latest version of DDR333,
without waiting any longer here you have the precious modules:
As you can see on the pictures above, the modules Kingmax delivered to
us are the first samples with Serial Number 0000043. For your information
the Module presented on the worldwide DDR-summit had S/N 0000045.
Compared to a regular DDR333 the DDR400 has almost the same height, in
order to accept high-density chips Kingmax voluntary kept the larger PCB
design, which allows at the same time to void any potential signal interference
in high-speed environments such as required by DDR400. For more information
about the TinyBGAä technology and the previously tested DDR333 we
invite you to check our previous article DDR333
:
|
The chips Kingmax uses to build the DDR400 are 5nS, so specified at 1/0.5e-9 = 200MHz. We are very impressed to discover here on this DDR-SDRAM the same speed rating which is more likely available on a GeForce2 Pro. Hereby a small overview on the commonly used access time and frequencies.
|
 |
As per the Kingmax label, the modules are certified CAS 2.5, we could
not expect less to guarantee a pure 200MHz single chip performance, 400
in Double Data Rate. So the DDR400 module offers a real 3.2Gb/S data throughput,
now we need to find the right hardware to handle this brutal power. It's
not enough to offer this performance while your CPU can't handle it. You
would never gain any performance, like it would be the case in the previously
tested KT333, which offers a respectable 2.7Gb/S with DDR333 on an EV6
Bus, with an Athlon who only requires 2.1Gb/S because it only runs at
a 133MHz clock frequency.
As we can see here, using a DDR333 or even a DDR400 on an Athlon XP running
on its standard bus at 133MHz (DDR266) has absolutely no use…! That's
why it's absolutely required to increase the system bus first, in this
case the Athlon system bus, from 133MHz up to 200MHz in which case the
EV6 will take all profit of the 3.2Gb/S instead of the standard 2.1Gb/S.
This will offer you all the benefit of the DDR400 performance. Regarding
the Pentium IV, it requires this 3.2Gb/S throughput to run under optimal
condition, without having to be restricted by the memory. Usually a Pentium
IV acquires this throughput of 3.2Gb/S by using a two-channel PC800 RAMBUS
module… but with the use of this DDR400 one single channel would
be enough!
Unlike the Athlon CPU, the Pentium IV has the ability to take full profit
out of a DDR400 module, and this in two different operational ways:
- Asynchronous Bus: This means that the CPU has the ability to run at a different speed than the memory. But even at 100MHz bus speed the Pentium IV will require a 3.2Gb/S throughput. Anyway, you will always take profit desynchronizing the CPU from the RAM and you will take 100% usable advantage out of it.
- Synchronous Bus: This means that the memory and the CPU run at the same frequency (FSB). In the present case at 200MHz, which is the basic chip frequency of the DDR400. Knowing that the original bus frequency of a Pentium IV is set at 100MHz, this would require a 100% overclocking to bring this CPU at full 200MHz FSB (800QDR)
Taken together, if we want to take full profit out of these memories, we need a CPU that can handle this FSB. Therefore we assume that the Athlon will cause most trouble with the DDR400, because the Athlon will require a synchronous bus to be able to test the memory. Let's take a look at these tests: