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440bx chip swap with 440gx

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First post, by dm-

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Hello community

I was thinking to swap a 440bx chipset on my board to 440gx to get a 2gb of ram support.

according to datasheet, 440gx has a new signals MAA14/MAB14 (AE22/AE23) which is n/c on 440bx.

the question is, where to this signals must be connected on SDRAM side? some ppl thinking they must go to A12 signal lines of SDRAM, but they're already connected to MAA12 signals.

is there any boardview for 440GX boards available on internet?

Reply 1 of 22, by myne

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Yes. Google 440bx and 440gx reference design.

Or see my sig for the bx.

It won't be easy but at least maa14 and mab14 are in the edge of the core

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Re: The thing no one asked for: KICAD 440bx reference schematic

Reply 2 of 22, by dm-

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The attachment photo_2025-01-14_09-34-18.jpg is no longer available

thanks!

looks like i have to disconnect A12 from MA12 and connect to MAA14/MAB14

Reply 3 of 22, by myne

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Maybe. You might need an expert to confirm or explain a workaround.

Why? Because imagine its a spreadsheet.
Will you care that m14 is actually L13 and vice versa as long as it looks right and works?

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Re: The thing no one asked for: KICAD 440bx reference schematic

Reply 4 of 22, by dm-

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that's why i asked for any 440gx boardview

Reply 5 of 22, by myne

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They don't seem to exist.
I've looked.

If you manage to find one, let me know.

You did find the gx reference schematic, right?

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Re: The thing no one asked for: KICAD 440bx reference schematic

Reply 6 of 22, by myne

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This guy knows ram making total 32MB 72-simm with 2MB*4 chips

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Re: The thing no one asked for: KICAD 440bx reference schematic

Reply 7 of 22, by dm-

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so, i did swap. the good news, its working:

The attachment photo_2025-01-27_07-26-17.jpg is no longer available

the bad news. it's working not as expected.

by default pins A12 and BA1 are connected to each other:

The attachment MAB12.png is no longer available

so i did disconnect A12 from BA1, left connection MAx[12] to BA1, and connected A12 to MAA[14] directly and...

The attachment photo_2025-01-27_07-26-02.jpg is no longer available

(this is first attempt, A12+BA1->MAA14 . later i rewired)

it does not work. logical levels on signals MAA[14] and MAB[14] are always low.
i connected MAB[14] to pull-up resistor and i can see logical level HIGH for a moment after power-on, then chipset pulling level down.
i even did try use bios from some GX mobos, same here.

what else did i miss?

Last edited by dm- on 2025-01-27, 05:27. Edited 1 time in total.

Reply 8 of 22, by myne

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The pads.

They're probably not NC. Possibly at the dimm end too

What board?

Last edited by myne on 2025-01-27, 05:26. Edited 1 time in total.

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Re: The thing no one asked for: KICAD 440bx reference schematic

Reply 9 of 22, by dm-

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MAx[14] are N/C on any bx440 board.

this is GA-6BXC

A12 and BA1 of the DIMM are connected to each other and MAx[12] of the BX440 chipset.

that's why there is a wires to this pads.

Last edited by dm- on 2025-01-27, 05:41. Edited 2 times in total.

Reply 10 of 22, by myne

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Yeah, they're supposed to be NC.
But the reason 7th gen got a slightly different socket is that motherboard makers earthed NC pins on 6th gen boards.

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Re: The thing no one asked for: KICAD 440bx reference schematic

Reply 11 of 22, by dm-

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they're not grounded. i did pull-up and there is a HIGH for a milliseconds after power on, then chipset pulling signal down

Reply 12 of 22, by myne

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Without ram?
I can't find a boardview for that board 😒

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Re: The thing no one asked for: KICAD 440bx reference schematic

Reply 13 of 22, by dm-

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with or without. it does not matter
256mb sticks works as usual, none of 512 or 1gb sticks are working

Reply 14 of 22, by myne

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I mean: without the ram installed, and the machine off, it is open circuit?
And with no ram, it still pulls down?

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Re: The thing no one asked for: KICAD 440bx reference schematic

Reply 15 of 22, by dm-

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when power off there is no continuity to GND or any other pads, resistance Mohms.
Connecting tester with Diode mode show ~ 0.4 v. drop on both pads. this mean chip is alive and there is connection to the pads

Reply 16 of 22, by dm-

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looks like gigabyte messed up DIMM slots.

The attachment bx.png is no longer available

according to the actual wiring from bx to dimm. BANK2 is actually BANK 0, and etc...

will do rewire MAx[14] according to this new info this evening.

Reply 17 of 22, by myne

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Nice one.

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Convert old ASUS ASC boardviews to KICAD PCB!
Re: A comprehensive guide to install and play MechWarrior 2 on new versions on Windows.
Dos+Windows 3.11+tcp+vbe_svga auto-install iso template
Script to backup Win9x\ME drivers from a working install
Re: The thing no one asked for: KICAD 440bx reference schematic

Reply 18 of 22, by dm-

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rewiring did not help much -)

i connected oscilloscope to A12 DIMM socket pin and what i got:
board starting, post codes running, init vga adapter, and then, on post code 52, there is a 2 HIGH levels on that signal coming from chipset...

The attachment maa14.jpg is no longer available

startup video file link : https://drive.google.com/file/d/1gmHo5WDbsiVF … jeImOoyYsHcOJq9

Reply 19 of 22, by Cosmic

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I have no advice for you as this is beyond my technical expertise. However, I wish you good luck and admire your public efforts. Please continue documenting your work for future viewers. This is interesting, informative, and educational!

UMC UM8498: DX2-66 SX955 WB | 32MB FPM | GD5426 VLB | Win3.1/95
MVP3: 600MHz K6-III+ | 256MB SDRAM | MX440 AGP | 98SE/NT4
440BX: 1300MHz P!!!-S SL5XL | 384MB ECC Reg | Quadro FX500 AGP | XP SP3