Can somebody please help me with my X1900's memory speed?

[blane]

I thought this card, the X1900XTX, was supposed to run stock at 650MHz and 1550MHz.

According to my ATI control panel my GPU is at 650MHz and the memory is at 775MHz.

Am I supposed to double the memory number or something? I overclocked them to 689MHz and 797MHz respectively.

Does this all sound normal to you? My 3DMark06 numbers went up 1000pts just by upgrading my 7800GT to this card and games are much better so I am pleased with the performance, I'm just curious why the memory speed is reported as half of what it should be. Screen shot below.

http://home.comcast.net/~bartalane/ati.jpg

Thanks for any help.

 

[CurDoG]

Normal...I had the same fears. Follow this thread for a detailed explanation.

Follow this thread.

 

[AzNPinkTuv]

775 is what its really running at but since its DDR memory, double it =)

 

[blane]

I see. Thanks for resting my concerns. I figured it was something like that.

 

[jiffylube1024]

Originally posted by: blane
I thought this card, the X1900XTX, was supposed to run stock at 650MHz and 1550MHz.

According to my ATI control panel my GPU is at 650MHz and the memory is at 775MHz.

Am I supposed to double the memory number or something? I overclocked them to 689MHz and 797MHz respectively.

775 MHz is the actual clockspeed. 1550 MHz is the effective clockspeed, since it's DDR (double data rate).

It's just like regular DDR memory: PC3200 RAM runs at 200 MHz, but it is effectively 400MHz RAM.

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As a little side note, I believe RAMBUS used QDR technology (transfers 4 times per clock speed), in addition to super high clockspeeds, so PC800 RAMbus RAM ran at 3200 MHz effective clockspeed (800MHz * 4) I'm pretty sure. However, RAMbus memory also runs on a very narrow bus (16-bit), so PC800 RAMbus RAM at 800 MHz on a 16-bit bus was only equvalent to PC3200 DDR memory at 200 MHz on a 128-bit bus (dual channel). I may be wrong and RAMbus may have been only using double data rate on a 32-bit bus (16-bit memory in dual channel) however.