6600 GT AGP card

The 6600 GT AGP top, PCI-E board bottom

6600 GT AGP and PCI-E X700 PRO 256MB

Another shot of the 6600 GT cards

Revised specs

Unfortunately, the GeForce 6600 GT AGP doesn’t match the PCI Express card spec for spec. While the GeForce 6600 GT AGP features the same 500MHz core clock frequency as the PCI Express card that was launched earlier this year, NVIDIA clocks the GeForce 6600 GT’s memory at 450MHz (900MHz effective), this is 50MHz slower than the PCI Express 6600 GT’s memory speed. This change drops peak bandwidth from 16GB/sec on the PCI Express 6600 GT, to 14.4GB/sec on the AGP card. Other than this difference, the rest of the 6600 GT’s core specs are the same as the PCI Express variant (although of course, you should also keep in mind that SLI is a feature that’s exclusive to the PCI Express GeForce 6600 GT, AGP cards cannot be combined together for increased performance).

Reference board design

With the revised memory clock speed in mind, the first component we looked at when receiving our reference GeForce 6600 GT board was its memory. Sure enough, NVIDIA uses the same Samsung 2.0ns GDDR3 modules for the GeForce 6600 GT AGP as they do for the PCI Express card and the GeForce 6800 GT. These modules are officially rated for operation at up to 500MHz, so you have a little bit of headroom for overclocking if you’d like to overclock your 6600 GT AGP board’s memory.

Looking over the Samsung Semiconductor website reveals that the 2.0ns GDDR3 modules are currently the entry-level GDDR3 offering for Samsung at the moment, there is no listing for a 2.2ns, 450MHz module. Therefore, as long as the retail GeForce 6600 GT AGP cards that are hitting the market are using GDDR3 modules, we feel pretty confident in saying that the boards are using 2.0ns memory, at least for right now. If you happen to come across a GDDR2 or DDR 6600 GT board however, all bets are off, as Samsung does produce 2.2ns GDDR2 and DDR SDRAM modules. At launch we were told that all PCI Express GeForce 6600 GT cards would ship with GDDR3 memory, so hopefully that’s also the case for the AGP card as well.

Note the rotated core and memory

Dual DVI connectors

One change you’ll immediately recognize is the dual DVI outputs on the GeForce 6600 GT AGP reference card (the reference shots provided by NVIDIA feature a 6600 GT with a DVI/VGA combination). By providing dual DVI connections, end users can combine a more flexible array of display combinations; this should come as welcome news for flat-panel users. With NVIDIA handling all early GeForce 6600 GT AGP board production, board partners like ASUS, BFG, eVGA, and PNY should all be providing dual DVI 6600 GT AGP cards. The XFX card listed on Newegg also sports dual DVI connections.

The second major difference you’ll notice is the orientation of the 6600 GT graphics core. In order to make room for the AGP bridge chip (NVIDIA marketing refers to it as HSI, which is short for high-speed interconnect), NVIDIA rotated the graphics core and its memory approximately 45 degrees. The bridge chip is then placed directly beneath the graphics core, at an angle parallel with the edge of the board. A second heatsink is used to cool the bridge chip, this heatsink is rotated 45 degrees off-axis of the bridge chip in order to fit properly. The aluminum heatsink used to cool the graphics core is the same cooler used on the PCI Express GeForce 6600 GT and does not cool the board’s memory.

By rotating the NV43 graphics core and its memory 45 degrees, NVIDIA is able to drop the bridge chip on the same PCB as the PCI Express GeForce 6600 GT. This is important for keeping production costs down.

You will however notice that unlike the PCI Express GeForce 6600 GT, the AGP GeForce 6600 GT requires an external power source. The AGP interface just isn’t capable of supplying enough juice for the card. If you don’t plug up the board’s power connection, it will operate at slower clock speeds.