ATI X1950XTX, X1650 Pro and X1300XT

INTRODUCTION

A quite nice day in August I flew over to Berlin for a one day Techday with ATI to see their new products for this fall. Unfortunately these new products didn’t include the R600 but that was to be expected. Fall is usually the time for a minor refresh-product and Vista isn’t out yet anyway so showing off a DX10 product now would be useless.

There are three minor fall refresh products that I will talk about today.

X1950XTX and X1950XTX Crossfire Edition
This is of course ATI’s new flagship product. Based on the R580 Plus this is an updated X1900XTX with GDDR4-memory support.

X1650 Pro
This is ATI’s new mid-level card.

X1300XT
A new entry-level card.

New memory – GDDR4

Before we move in and talk about the individual cards, let’s take a look at the main enhancement with these cards – the support for the new GDDR4 memory. We had the luck of having one of the guys behind the memory with us at the Techday, ATI’s Senior Director, Circuit Technologies Joe Macri, who told us a bit more about the new advantages that we get with the new memory.

Low power by design

GDDR4 has been developed with low power requirements in mind from the start. If we look at GDDR3 vs GDDR4 we find:

The VDD is lower on GDDR4 than on GDDR3.
The nominal voltage for GDDR4 is 1.5V. 1.9V is used for gaming or overclocking. This gives a 30% save compared to GDDR3.

Fixed data burst length of 8.
This lowers the core frequency by 2x compared to GDDR3, significantly reduces the power and thus allows for higher clock frequencies.

Joe Macri showed us some of the ways they managed to do all this and while I won’t pretend I understand everything you might find this interesting.

DBI – Data Bus inversions

This lowers power consumption and increases the speed by reducing VDD-noise.
How it works? Well, by trying to eliminate the Logic 0’s as much as possible as they are the only ones that use power.

They use a formula that says that if the 0’s are >4 then invert the data and set the DBI-flag to 1. The receiver will then invert it back due to the flag.

Examples:
Original Data = 00000000 => Since # 0’s >4 Invert
Data on Bus = 11111111, DBI = 1
When DBI = 1 => Received data = 00000000

Original Data = 11111000 => Since # 0’s <4 Do not Invert
Data on Bus = 11111000, DBI = 0
When DBI = 0 => Received data = 11111000

Lower input Capacitance

GDDR4 has lower input capacitance than GDDR3 meaning lower power and more speed.

Double Pumped Address Bus

GDDR4 uses ½ the pins for address than GDDR3

• Slight reduction in Power
• Frees pins up to be used for Power and Ground
• Increases Speed
• Address are sent on two consecutive cycles