Debut of AMD AM2: the long-awaited DDR2 on AMD Athlon X2
Date: 23.05.2006
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Author: Vladimir Romanchenko, Dmitry Sofronov
This day can be called a reference point of the new epoch of
AMD's processor architecture. It's just today when AMD has announced a
start of delivery of dual-core AMD Athlon 64 FX-62 and AMD Athlon 64 X2
5000+ processors compatible to the new AMD Socket AM2, which support
the AMD Virtualization technology and non-buffered DDR2 memory. Of
course, along with the top-end processors there has been announced a
whole line of new chips AMD Athlon 64 X2, AMD Athlon 64 and AMD Sempron
compatible to the Socket AM2.
Indeed, the long-awaited implementation of support for the
DDR2 memory by AMD chips is undoubtedly an eminent event, although the
processor core this time hasn't undergone any radical changes. The
single- and dual-core processors for the new Socket AM2 that have been
announced today offer a new controller with support for the DDR2. Along
with that, for the first time there has been implemented support for a
number of new technologies, with the operation of already known
functions optimized, and several other architectural innovations
introduced. However, in terms of evolution it doesn't reflect anything
more than the new core stepping - Revision F. Consolidating the real
architectural innovations announced today, we can count the following
four points:
- Support for DDR2 SDRAM memory
- Support for the AMD Virtualization (AMD-V)
- Implementation of processors with economical power
consumption
- Implementation of support for the 2-channel memory by
Sempron family processors
The key event underlying the transition to anew version of AMD
processors for desktop PCs with the new 940-pin AN2 socket is the
implementation of support for the DDR2 memory. Since the memory
controller is integrated into the processor, the major complication of
the stage is not the emergence of new memory chips (fortunately, the
DDR2 has already gained wide occurrence and even gone down in price),
and even not the emergence of some special chipset versions for the new
platform (although, the need for good chipsets has always been there).
The major point is how well AMD has managed to implement this
integrated controller with support for the DDR2,
To start with, let's sort out all the information on new
chipsets available to date and then move on to running the tests.
Architecture
The new AM2 processors by AMD are 940-pin K8 chips for desktop
systems with support for the 128-bit DDR2 aimed at the new Socket AM2.
From this point onwards, retail shops will be receiving more and more
AM2 versions of AMD chips for all the market sectors - Athlon 64,
Athlon 64 X2, and Sempron. These chips are consolidated by the DDR2
version of the Revision F processor core, although each sector has its
own code name.
- Windsor - dual-core Socket AM2
processors Athlon 64 FX and Athlon
64 X2 with support for dual-channel DDR2-533/667/800 and
the Pacifica technology. They are produced following the 90-nm process
technology with the use of SOI; they offer 2 x 1 MB L2 cache,
- Orleans - single-core Socket
AM2 processors Athlon 64 with support for
the dual-channel DDR2-533/667 and the Pacifica technology. They are
produced following the 90-nm process technology with the use of SOI;
they offer 1 MB L2 cache,
- Manila - single-core
inexpensive Socket AM2 processors Sempron
with support for the dual-channel DDR2-533/667 memory. Are produced
following the 90-nm process technology using SOI; offer 512 K L2 cache,
Although that is some deviation from the topic, I must point
out that with the mass emergence of DDR2 versions of cheap AMD Sempron
chips expected already this summer the epoch of wide use of the DDR1
memory can be regarded as quickly coming to a demise. In this regard,
the quickness is of course a relative thing, and there are no plans yet
to close down production of Socket 939 processors, but anyway that
should be a distinct sign for reasonable buyers...
The new revision F with the former 90-nm process technology,
support for the fast memory up to DDR2-800, declared Pacifica
technology, economical power saving have called foe some internal
re-design. On the photo below, where dual-core chips of revisions E and
F are compared, the easiest to see is the increased pad between L2
caches.
Windsor VS ToledoActually, the drawing reproduces the scale in merely a
schematic view. In fact, the area of the new core of Rev. F has been
increased relative to version Rev. E by approximately 13% - up to 220
sq.mm (from 194 sq. mm). Therefore, the size of 1 MB L2 caches has been
increased accordingly by 18%, so has the size of 1 MB L2 caches
– from 106 sq. mm in Rev. E (in the first steppings - 115 sq.
mm) to 126 sq. mm in processors of Rev. F. At the same time time, the
areas of positioning SRAM L2 cache memory has gone down. While the 1 MB
L2 cache size in Rev. E takes 41.4 sq. mm (therefore, 82.8 sq.mm for
the dual-core structure), this indicator in new processors of Rev. F
has gone down to 38.7 sq. mm (77.4 mm in the dual-core version).
The number of transistors that constitutes each chip has gone
up. While in today's dual-core K8 processors there are 233 mln
transistors, then in chips of Rev. F there are 243 mln, that is, by
approximately 4% greater. There is a complete analogy with single-core
processors: 120 mln transistors in the single-core K8 chip have been
replaced with 129 mln transistors in the processor of Rev. F, where the
increase is even greater - i.e.by 7.5%.
Increase in the core area with the reduction of cache area and
the same process technology for the manufacture of processors of Rev. F
suggest some reasoning. Indeed, AMD K8 chips of steppings Rev. D and
Rev. E have been produced following the same 90-nm process technology
PD-SOI (Partially Depleted Silicon-on-Insulator), with a 9-layer copper
metallization.
Therefore, the area of SRAM cells in the cache has gone down,
the number of transistors has gone up, so has the total area of the
chip. Of course, all can be attributed to the new DDR2 memory
controller (indeed, support for DDR2-800 in exchange of DDR-400 called
for substantial remake of signal lines) and support for the Pacifica
technology, but it seems to me something will be "ticking" in these
processors for the time being. For instance, integrated but not yet
declared support for the Presidio technology (an analog to Intel's
LaGrande). For now it is still unknown what to do with the
virtualization – AMD Pacifica, like the 64-bit computing
implemented in the architecture, may also wait until the emergence of
the new generation of Microsoft Vista operating systems.
Indeed, judging by the latest publications online, a
substantial redesign of the core (the core, not the memory controller)
is expected with the release of further steppings - Revision G and
Revision H. In the case of Rev. G, at least a substantial redesign of
the branch processing module is expected, and in Rev. H - even a new
generation of the FPU (Floating Point Unit).
Schematic sketch of potential cores of Rev. G and Rev. HIn this article, it doesn't make any sense to dwell on the
details of the next generation of AMD64 architectures; anyway, I would
note the newly born revision of the core hasn't undergone any
substantial redesign which directly affects the performance. In other
words, the performance boost, albeit expected, is possible only through
the rise in clock speeds and implementation efficiency of the new
memory controller.
However, there is one more substantial change implemented in
new AM2 processors of revision F, because chip versions with varying
power consumption have been declared. Now, AMD will produce economical
processors for desktop PCs of the Energy Efficient Desktop Processor
class. This category includes a number of new Socket AM2 chips AMD
Athlon 64 X2, AMD Athlon 64 and AMD Sempron with support for AMD
Cool‘n’Quiet and improved power consumption. The
new economical chips will be grouped into two subclasses - one with TDP
65 W and one with TDP 35 W.
Just imagine that now you can come across three versions of
the chip with a very similar name in the retail shop - AMD Athlon 64
3500+ or 3800+ , one of them being "regular", with TDP 89 W, the other
one - Energy Efficient, with TDP 65 W and finally the third version -
Energy Efficient Small Form Factor Desktop Processor AMD Athlon 64 X2,
with TDP 35 W. Processors AMD Athlon 64 3500+ and 3800+ will be
represented in versions for Socket 939 and Socket AM2, the same is for
the case with AMD Sempron 64 3000+, 3200+, 3400+, 3500+, and 3600+
processors.
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