LOSTCIRCUITS

Under The Hood

Disclaimer: The following information is provided for educational purposes only and LostCircuits will not assume any liability for any consequences whatsoever arising implicitly or explicitly from reading the material presented in this article!!

We earlier alluded to the fact that the core is identical in all X800 models, however, there are differences in the level of enabling of the different features. In addition, yield issues may play a role as to what parts are capable of running all four pipeline blocks at full bore and at a core speed of 520 MHz as opposed to the 3/4 solution sporting a meager 475 MHz core frequency. Similar issues hold, at least in theory, for the memory, the Samsung K4J55323QF-GC20 GDDR3 components in 144 pin BGA format are rated at 2.0 ns, which translates into 500 MHz rated clock rate or 1,000 Mbps data rate. Needless to say that there are higher speed grades available, the fastest of which are at the time of press at 800/1600 MHz clock/data rate.

           

Left to right: Close-up and personal with GDDR3. --- GPU die markings: the xxx.1 supposedly identifies a fully functional core (quality grade 1). Note the two bridges at the top right corner, one of which has been cut. --- Zooming in on the bridges: The one of the left has the bridge cut. --- Rear Window defroster repair kit should become a household item, in this case, we used it to bridge the cut trace as shown

The Core by Numbers

Different grades of the R420 appear to be differentiated by different markings to designate the quality grade. In absence of hard information, we have to resort to the hear-say circulating that the xxx.1 cores are fully functional and can be enabled to run in XT-mode, that is with all four pipeline blocks enabled. Enabling the functionality requires a BIOS flash with the -XT binaries AFTER physically reconnecting the cut traces on the package. To give credit where credit is due, we got the idea for this procedure from this article on PCUnleash.

The Operation

To make a long story short, all we did was to bridge the cut trace at the upper right corner of the package and subsequently flash the card's BIOS with Flashrom.exe. The flashing procedure requires a number of switches, first it is advisable to simply run the -i switch to gather all relevant information from the card. For a successful flashing of the graphics adapter, it is further necessary to use the -p switch for writing the binaries to the EEPROM, and the -f switch for forcing the procedure.

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