I finally got multipliers to work on my Asus A7M266 DDR board!

[AdamK47]

I bought 256MB of PC2100 memory and an Asus A7M266 two days ago and in those two days I've been playing around with it trying to get my 1.2GHz Athlon to run at 9 x 133. I bought a block of DIP swiches from Radio Shack and soldered it to the board. I set the 5th & 2nd DIP down and powered on, but got nothing. Not even a signal. I checked the DIP swiches to see if they were indeed on there correctly and they were. I then began connecting the L4,L3, and L6 bridges to see if there was a combination between the swiches and bridges that would allow for multiplier manipulation. Connecting all of the L4 and L3 bridges allowed me to use all the multiplier swiches but one... the 2nd one. That was the one I needed too, so I played around with the bridges some more. I found that connecting all of the bridges on L4 and L3 except for the second L3 bridge allowed me to use the second DIP switch, but disables the first switch. I don't care about the first switch, since all I need are the 2nd and 5th switches. Now, with that combination I'm able to run my 1.2GHz Athlon at 9 x 133MHz with my PC2100 memory at its rated 266MHz DDR speed. This thing rocks!

 

[DarkMajiq]

Couldn't you just have modified the multiplier using the L3, L4 and L6s alone, without bothering with all the DIP switches and such?

 

[AdamK47]

I tried that, but after two hours of trying to cut through ceramic on one of the bridges I gave up and did this mod instead.

 

[johncar]

Adam....,
Go here http://members.nbci.com/candjac/index.htm Duron/Tbird OC article to see the circuits you were manipulating. Just a few comments 'cause not exactly sure if you were counting from the L or R,

You'll see that your default L3/L4 bridges setting had the HI bridge for the 1X "Adder" closed. The other 3 bridge "pairs" for the .5X, 2X, 4X, "Adders" had their LO bridges closed. Those settings result in a TotalX = 4X = 3X base + the 1X Adder set HI. Then 4X is interpreted as 12X since 3X thru 4.5X get 8X added, algorithm is there at the site.
(Only one bridge of each "pair" is closed to set either a HI or a LO).

So in order to reset to TotalX = 9X = 3X base + 2X + 4X Adders set HI, you had to reset the default HI 1X to LO, and reset the default LO 2X and 4X to HIs.

But the way you did this is wild. When you close "both" bridges of each pair the signal bus sees 1/2 of the voltage between gd aand Vcc = Vcore. 1/2 signal voltage is usually "indeterminate", ie, not sure if the comparator in the chip will interpret it as a HI or a LO. But from what we can see from your description, the 2X and 4X signals were interpreted as HIs in order to enable the 2X and 4X adders.

Opening the 2nd L3 bridge seems to have just restored the .5X circuit back to its default LO, Adder Off, setting. And if your "second" switch was connected to the 1X "pair", then that's how you were somehow able to turn off the default 1X Adder...by grounding the 1/2 Vcc signal, resetting it to a LO.

Copy and print this out, then check to see if and how it fits what you did, after you go to the site with the pics, circuit diagrams, etc.
Man, if you managed to do what you did, blind as it seems, you get some kind of prize.;-)
John C.

PS:- Info at site may help you to do it the simpler way described at the site...there's even a page describing the A7V control circuits, which might be similar to yours. Give a response in any case.

 

[AdamK47]

Your right. I had no idea what did what. I just experimented with it a lot. I found it odd that just adding the DIP switches did not override the default chip settings even though DIP switch 5 is supposed to disable default chip FID settings. I have a question for you....

How would I be able to use all of the multiplier switches with a 1.2GHz T-Bird (default 12 x 100) without cutting any of the bridges? It looks like you know a whole lot about this. I don't know if the information on the site about the A7V will apply with the A7M266.

 

[johncar]

Adam...you wrote.....
How would I be able to use all of the multiplier switches with a 1.2GHz T-Bird (default 12 x 100) without cutting any of the bridges? It looks like you know a whole lot about this. I don't know if the information on the site about the A7V will apply with the A7M266.
End quote.....

First...see if you can locate (2) 74F125 quad tri-state buffer chips on the mobo. If they are there then you can verify the circuitry on page 3 of our site and correct whatever is wrong or different from the A7V. But if they do not exist, you will have to follow the procedure for DIY dipsw's...which you will note means cutting some of the FID L6 bridges to remove the "hard grounds" default signals which "cannot" be over-ridden. (Note that the tri-state buffers can "effectively" open those circuits). Note carefully on the FID circuit diagram/s that all AMD does is to ground those default HI circuits it wants to be LO. ..these "signals" go to chipset, not to the cpu...again all AMD does is ground them or not. So if you open all L6 bridges then "you" can control the FID settings to the chipset simply by grounding the circuits for LOs, and leaving the switch/es open to ground to allow the default HIs to remain HI where appropriate...same as AMD did.
Reference to DIY diamond surfaced hand tool for easy ceramic/bridge cutting on page 2...with link to supplier MicroMark.

Second... the DIY dipsw's circuit for the BP_FID settings do not involve any L3 or L4 bridges cutting, as the default settings can be simply over-ridden by the circuits shown. Of course the L1 bridges must be closed as they are part of those circuits. But believe they are closed on 1.2Mhz chips...easy to close with rear window defogger repair kit conductive ink in any case.

Hope this helps if you want to make OC operation more understandable. On the other hand, you seem to be where you want to be, and if happy there, you can decide to leave well enough alone for the time being, at least until the OC bug bites again.;-)
John C.

 

[AdamK47]

I tried other settings with the L3/L4/L6 bridges along with the DIP switches, but I think I need to cut some of the L6 bridges. I don't want to do that. Thanks for the information though. I think I'm going to leave it at the settings I indended to run it at. I got everything running cool. The 1.2GHz chip runs fine with only 1.55V with the VIO1 at 2.7V and VIO at 3.3V. It runs much cooler than I would have expected. Even after about 12 hours of Pime95 last night. I guess I'll change my sig so it doesn't say space heater anymore. hehe

 

[AdamK47]

johncar,

As you stated before, the overclocking bug has hit me again. This time I was armed with more information on how to get all of the multipliers working. I was over at the AMDZone forums and did a search for A7M266. I got a result with a post from a guy that suggested removing the 4.7K Ohm resistor banks RN19 and RN20 and replacing them with lower value 330 Ohm to 560 Ohm resistors. This will allow for the voltage signal to pass through the lower resistance. After searching my old dead motherboards, I found two good 330 Ohm resistor banks (identified by 331 resistance code). I used a flat edge soldering iron to heat up the four contact points on one side to remove them easily. I did the same to the 4.7K Ohm resistors on the A7M266 being very careful not to damage the contact pads.

Now heres the tricky part. To get the 330 Ohm resistors on the A7M266 motherboard I had to be very careful and have a steady arm. After several attemps (about 4 frustrating hours) to get all 8 points of each resistor to touch the contact point without touching each other, I got them on there. If I had better equipment, this would have been a breeze. After that, I used my multimeter to confirm that each of the four points were in series (RN20 in series with RN19) did add up to 660 Ohm and that they were in contact with the motherboard.

Now, with everything in place, I can now use every single multiplier setting through the dip switches without having to pencil anything in on my Athlon 1.2GHz.

And yes if your wondering, I have experience with electronics. It wasn't too long ago that I went to college to get my Assoc. Degree in Computer Systems Tech., so I somewhat knew what I was doing.