8800GTS 640MB/320bit -> 768MB/384bit

**largon** · 07-09-2007, 12:36 PM

I'm toying with an idea of modding the 320bit bus on the 8800GTS into 384bits...

You know, the 8800GTS has 12 GDDR chip solder pads like 8800GTX but only 10 are populated and the GPU (mem ctrl) is the same. So, I'm thinking why not? I got the needed chips, two (eight actually) Samsung K4J52324QE-BC12s, the SMD caps, resistors and what-not needed for the pads on the backside. But most importantly soon also a hot air soldering iron for soldering the BGA balls...
Sounds reasonably safe, doesn't it? No?

Anyways, the "only unsolved problem" (yeah right) is to mod the BIOS from 320bits to 384bits.
Some thoughts about the bus width problem:
- NiBiTor 3.4a doesn't allow bus width manipulation
- reverse engineer the bus width bits from a BIOS of a GTX (mission impossible?)
- flashing a GTX BIOS into the GTS (atleast it "should" be reflashable back to GTS given the card were not to fry instantly)

Input would be appreciated regarding how to enable the extra bus width once the hackjob is done.

btw, the card is errr... relatively disposeable so there's no need for anyone to run around screaming "Don't do it man!!1!one1!".

**GrimReaper** · 07-09-2007, 01:02 PM

Originally Posted by largon

I'm toying with an idea of modding the 320bit bus on the 8800GTS into 384bits...

You know, the 8800GTS has 12 GDDR chip solder pads like 8800GTX but only 10 are populated and the GPU (mem ctrl) is the same. So, I'm thinking why not? I got the needed chips, two (eight actually) Samsung K4J52324QE-BC12s, the SMD caps, resistors and what-not needed for the pads on the backside. But most importantly soon also a hot air soldering iron for soldering the BGA balls...
Sounds reasonably safe, doesn't it? No?

Anyways, the "only unsolved problem" (yeah right) is to mod the BIOS from 320bits to 384bits.
Some thoughts about the bus width problem:
- NiBiTor 3.4a doesn't allow bus width manipulation
- reverse engineer the bus width bits from a BIOS of a GTX (mission impossible?)
- flashing a GTX BIOS into the GTS (atleast it "should" be reflashable back to GTS given the card were not to fry instantly)

Input would be appreciated regarding how to enable the extra bus width once the hackjob is done.

btw, the card is errr... relatively disposeable so there's no need for anyone to run around screaming "Don't do it man!!1!one1!".

the voltage changes would also be needed, the GTX eats up a lot more power than the GTS, I would think that this is really really impossible!

**largon** · 07-09-2007, 01:11 PM

I assume you're referring to the "GTX flash" -method?
I doubt a GTX bios in GTS would increase power consumption per se, except for the couple watts for the 2 additional chips. I think the locked shaders are beyond bios modding, infact I'm not looking to unlock shaders with a GTX bios.

**nutral** · 07-09-2007, 01:17 PM

the shaders shaders that arent used for the 8800gts are cut off with a laser, no coming back to them.

**largon** · 07-09-2007, 01:38 PM

nutral,
No, I doubt there's any laser cutting involved in the locked shaders; there's no cut nor live bridges on the GPU.

BTT, I'm not interested in the locked shaders.

edit:
I'd appreciate if someone would post a high res macro pic of the backside of the GTX particularly around the area of the 11th and 12th RAM chips that are not found on GTS. See attachment for reference.

**ineedaname** · 07-30-2007, 09:36 PM

I really hope some1 posts cuz this looks interesting

**zanzabar** · 07-31-2007, 12:58 AM

wouldent the set shaders have a set of instructions that only worked for the gtx/ultra, witch i would think would fry your card if u tried to make the chip run it, especially since nvidia dosnt use fully dynamic shader pipelines

**1badhabit** · 07-31-2007, 06:24 AM

This could indeed be very interesting, and a fun project if it could work. Ill try and get some Macro pics of the back of my GTS tonight.

**GripS** · 08-02-2007, 11:47 AM

Originally Posted by 1badhabit

This could indeed be very interesting, and a fun project if it could work. Ill try and get some Macro pics of the back of my GTS tonight.

He needs a pic of the GTX (not the GTS). I'm curious to see how this turns out myself.

**largon** · 08-06-2007, 12:48 PM

BIOS is the obstacle here.
Soldering doesn't make any good if BIOS doesn't know there's 12 chips instead of 10.

Btw, I found that the chips on my GTS aren't exactly of the same revision as the spares that are supposed to be soldered in. Both are Samsung, speeds match, etc, but the chip generations and current draws differ.

Anyways, I need a good macro of the backside of 11th and 12th chips (M11 and M12 on the silkscreen) of a GTX. And GTX only, since a GTS doesn't have the surface mounted components installed. I got myself a GTS here, can take all the pics I ever fancy about one myself.

zanzabar,
Dunno what you're talking about since I have no intention to tamper with the shaders.

**RAW-Raptor22** · 08-11-2007, 09:54 AM

This sounds like a good experiment, I would like to see how it turns out. If good comes to good:

320bit bus -> 384bit bus
320MB/640MB -> 768MB
(idealistically)96shaders -> 128 shaders

Good luck on the flashing!

**Alik4041** · 08-28-2007, 02:20 AM

/subscribed

If this works, I'm definitely getting on the boat with my gts

PS: I would recommend you get the SAME EXACT ram modules just to cancel out the variable of memory not compatible

Good Luck and let us know how it goes

**ginnz** · 09-04-2007, 02:59 AM

you can use a hot air gun to solder the bga..... ive worked with bga chips before. desoldering and reattaching, first, i use a small 15 watt iron with a needle point to "touch up" all the bga "balls", so they are all uniform. then apply a thin layer of flux.... line up the pads, and use something (clips, hemostats, whatever" to hold the bga in position, then heat the chip till the flux boils out the sides.... it should be good to go.

this sounds like a risky project.... i like it!

**largon** · 10-30-2007, 11:49 AM

It seems this mod is impossible.
The ROPs on G80 are coupled with a fixed portion of RAM bus width (64bit/quad) and since G80GTS has 20 ROPs (5 quads) the maximum RAM bus width it could possibly use is 320bit.

One would need to unlock the missing quad to make it work...