The AMD 790GX
chipset is designed for higher 3D and video performance than previous AMD
chipsets. It's the third integrated video chipset from AMD to feature DirectX 10
capability, and serves as the high-octane upgrade to AMDs popular 780G/690G
AMD's 790GX chipset supports all AMD 32-bit/64-bit
Socket AM2 CPUs, the new Socket AM2+ Phenom and Athlon processors, and the new
Phenom II Socket AM3 family (depending on what the motherboard manufacturer
builds). With a socket AM3 or AM2+ processor installed, the CPU communicates
with the AMD 790GX chipset over a HyperTransport 3 (HT3) connection. For legacy
socket AM2 processors, a HyperTransport 2 (HT2) connection is used.
The AMD 790GX core logic is built on TSMC's 55nm
manufacturing process, draws 0.95W power, and contains 205 million transistors.
By comparison, the AMD 690G contained 72 million transistors, drew 1.4W power,
and was fabricated on the 80nm process.
The 938-pin AM2+
socket. Socket AM3 processors are backwards compatible with AM2+ sockets,
but socket AM2+ processors are not forwards compatible with socket AM3
because the processor does not have a DDR3 memory
The AMD 790GX core logic is based on
the venerable 780G chipset, but with an overclocked integrated graphics core and
dedicated 128MB of DDR3-1333 side port memory. In every real sense, the AMD
Radeon HD 3300 integrated graphics is more an integrated videocard than a true IGP which leaches its memory from the
While the Radeon HD 3200 GPU integrated into the 780G
chipset ran at a 500MHz core clock speed, the Radeon HD 3300 that's part of
AMD's 790GX chipset has been bumped up to a 700MHz core clock. Other than the
increase in speed, this chip is quite similar to its older sibling. Both IGPs
are built on the 55nm manufacturing process, have 26 lanes of PCI Express
connectivity, connect to the processor with HyperTransport 3.0 and use AMD's
Unified Video Decoder to offload processing of high-definition H.264, VC1 and
M-PEG2 content from the processor.
The 938-pin AM2+
socket with a backwards compatible socket AM3 AMD Phenom II X3 720
The AMD SB750 southbridge is a different story, and has
changed quite a bit from it predecessor the AMD SB700 which was paired with the
AMD 780G chipset. This new southbridge now supports RAID 5, in addition to the
RAID 0, 1 and 10 functionality.
AMD's SB750 southbridge also makes use Advanced Clock
Calibration (ACC); this is an interconnect that runs directly from the
southbridge and into the CPU socket. For owners of AMD Phenom and Phenom Black
Edition CPUs, enabling ACC will allow the SB750 southbridge to tweak the
overclocking capabilities of their processors.
Due to the increased graphics capabilities of the
integrated graphics controller, the AMD 790GX chipset supports Crossfire X,
although at reduced bandwidth rates than can be found on non-integrated graphics
motherboards. The AMD 790GX's Crossfire is limited to x8/x8 lanes of PCI Express
bandwidth. While this clearly isn't as nice as having a x16/x16 Crossfire
configuration, it's still more than enough that even high-end graphics cards
like the Radeon HD 4850 won't become bottle necked.
M3A78-T motherboard has 128MB of 1333MHz DDR3 Sideport memory, which serves as a
high-speed cache for the Radeon HD 3300 before it has to dip into the DDR2
memory banks that are shared between the integrated graphics processor. As we've
seen from previous reviews, the Sideport memory does add a few extra frames per
second to the Radeon HD 3300's performance in 3D games, but usually it's still
not enough to make most modern 3D games playable.
Naturally, support for Hybrid Crossfire is also included,
which means that the integrated Radeon HD 3300 graphics processor can be paired
with a Radeon HD 3450 videocard, and when running together these two graphics
processors can be about as powerful as a Radeon HD 3650. While this is a bit of
an improvement in overall processing power, it's really not worth
Look at it this way, AMD Radeon HD 3450 videocards cost
around $50, and AMD 790GX-based motherboards can reach as high as $160. That's
more than enough money to get a $100 AMD 780G-based motherboard and a faster
Radeon HD 4670 videocard..... Running Crossfire or SLI on an integrated graphics
chipset has never been particularly compelling - it's a technology that's only
useful to gamers, but will barely ever give worthwhile performance in video
AMD Unified High Definition
Most recent integrated graphics chipsets from AMD, nVidia
and Intel have had the capability of connecting via analog or DVI monitor cable.
If the board supported DVI, that meant it was capable of HDMI should the
manufacturer choose to implement it.
The AMD 790GX follows a similar path with dual display
controllers supporting analog VGA and DVI/display port/HDMI outputs. Although it
would be nice to use a DVI monitor and output HDMI to an adjacent big screen,
with one digital display controller it's an either or situation; either DVI or
Display Port or HDMI (at least all are HDCP compliant). And don't think you can
use that DVI-to-Analog converter, you can't.
to push the ASUS M3A78-T to the limit. Overclocking is next!