8800GTS locked mem-controller, ideas and unsuccesful practice:)
Memory controller of NVIDIA G80 is made from six 64-bit channels. This is also visible in model range of existing cards, 8800GTS, which have blocked 1 channel and have no 2 memory chips.Total bus width cutted from 384 to 320bits. 384-64=320 :D So one of memory channels is disabled on such cards. Which exact memchannel is disabled marked on GPU IHS top. Number after letter K in line “G80-100-K0-A2” is the key. Here you have image for reference. total 6 channels (from 0 to 5)
http://tin.topmods.net/article/evga/memchg.jpg
"Full" cards like 8800GTX\Ultra\Quadro working with all 6 channels, so their chips have no any letters “–Kx”. Most popular cards with disabled "0" channel, Lurking in the web show off some other rare variants, with G80-100-K1-A2, and G80-100-K3-A2 and G80-100-K5-A2. All these cards are 320bit 320MB versions.
So we get the question, is it possible to enable all memory controllers, buy soldering extra chips and flashing BIOS in home environment? :confused:
To get practice with this I've got dead (crappy GPU) Radeon X1900XT 512MB, which have 8 mem chips SAMSUNG K4J52324QC-BJ11. These IC's are mostly the same as used in mine 640MB GeForce 8800 GTS, difference is only in timings (1.1ns Radeon vs 1.2 8800GTS) and nominal voltage.
http://tin.topmods.net/article/evga/xtmems.jpg
Soldering chips was made in a horror way, by electrical owen from ancient 196x's :ROTF: This metodic was twice tested by me earlier (here russian description with photos) for _SUCESSFUL_ replacing chips NVIDIA nForce4 SLI\Ultra on two motherboards DFI LanParty NF4.
http://tin.topmods.net/article/evga/memsr.jpg
http://tin.topmods.net/article/evga/memsr2.jpg
Except memory chips, there also passive resistors and capacitors necessary for normal videocard operation, which was not placed with 2 memories. Soldering them was made by usual iron with sharp tip and binoculair microscope MBS-9. After all these things I've installed card into PC and turn power on. No artifacts, it is working! Ok, flashed original BIOS from Quadro FX 4600, which have total 768MB and 384-bit memory bus. But unfortunely, I've got just Quadro FX 4600 with 640MB and 320bit.
So don't try to add memory to your 8800GTS, G80 on these cards have fully blocked controller. TESTED by me :D
P.S. Of course, we can try to replace G80 chip from GTX card to GTS PCB, and AFAIK, this will render working GTS 768MB 324bit with even 128SP, but have no any working GTX-chips :rolleyes:
P.P.S. sorry for watermarks on photo, I've used this material for russian online site in mine EVGA 8800GTS ACS3 card review.
TiN.