Re: Triple bios schematic/pcb design help
WP is active low, en542958.pdf page 19/20 suggests a pull-down resistor if the pin is being used. I think we need a pull up resistor as WP shouldn't be aloud to float.
The actual chips I have are GD25B64SIG from Giga devices, I could only find datasheets from similar devices....
modman1337
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Last Activity: 07-25-2019, 03:25 PM
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Location: grimsby
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Last edited by modman1337; 09-04-2015, 02:57 PM. -
Re: Triple bios schematic/pcb design help
Cheers STJ that's 100 times clearer mate.
I'll check the data sheet for the pull up resistor on WP.
I think you mentioned the 3 resistors to the dip being 100ohms?
Nice workLeave a comment:
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Re: Triple bios schematic/pcb design help
Excellent idea I like it, I was toying with doing the same thing with a custom flex but thought it might be pricey, this could work. Reminds me of console modchips for the wii.
With regard to the flip top I may see if there's a through hole version for ease of soldering, can it be done with the forma or would I need IR rework?
Feel free to play around with the schem and do what you thinks best.Last edited by modman1337; 09-01-2015, 04:25 AM.Leave a comment:
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Re: Triple bios schematic/pcb design help
thats it stj albeit quite a messy schem, first time using eagle had to spend sometime getting to grips with it. does it need modifying?
Until I can come up with an ingenious way of connecting to the soic land pattern on the mobo im using the right angled molex connectors and an off board slide switch.
[URL]http://www.logicalsys.com/prodpics/soic-emulator-adapter-150.jpg[/URL]
Would these headers do the job? we could then have a connector on the back of the board to interconnect, if its strong enough....Leave a comment:
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Re: Triple bios schematic/pcb design help
Just a quick update to show my progress on this project, eagle files attached.
Let me know what you think....Last edited by modman1337; 08-31-2015, 02:20 PM.Leave a comment:
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Re: Bad contacts problem. How you deal with it?
U'd be wasting your money on that stuff as suggested get yourself a rubber I use Staedtler Mars Plastic Eraser, then some IPA on a cotton bud and rub down to make sure and ur good to go.
The IPA has so many uses, I clean screens and keyboards with it also.Last edited by modman1337; 08-23-2015, 11:01 AM.Leave a comment:
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Re: Triple bios schematic/pcb design help
Of course, I don't know what I was thinking mixing gnd with cs.
Anyway now onto pcb layout, get this mother etched.
Great stuff STJ, without ur input I'd still be scratching my head, or maybe have a burnt out board.
Any comments or ideas for features from the community welcomed.Leave a comment:
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Re: Triple bios schematic/pcb design help
sure flip top socket types are not idea, the main thinking was I didn't want the overall design too tall, with the restricted height inside my laptops case.
Probably going to reduce the project to a two chip solution in the end or do two versions, just nice to have the option of a removable chip without having to get the rework station out and de-solder.
so the cs pins can just be ignored entirely and left floating?Leave a comment:
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Re: Triple bios schematic/pcb design help
I guess it'll be trial and error regarding cmos settings, may just have to clear cmos before switching maybe?
Not a big problem as i can manipulate the bios setup IFR (internal forms representation) to change a default value.
yes 3 switches does seem daft, left first chip cs grounded only.
As we have a test socket on the board what is the risk if any of esd damaging the other chips in the circuit? (possible frequent removal/insertion of chip)...Last edited by modman1337; 08-18-2015, 10:19 AM.Leave a comment:
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Re: Triple bios schematic/pcb design help
here's what I have so far.....Leave a comment:
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Re: Triple bios schematic/pcb design help
Whilst drawing the new schematic I realised that if we're switching via Vcc CMOS memory on inactive chips isn't getting any power therefore bios will resort to setup defaults every time we select a different chip so any saved values are lost.
Can this be resolved in any way?Leave a comment:
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Re: Triple bios schematic/pcb design help
Thanks STJ,
Some great advice there I'll come up with a new schematic and see what you think. So without the pull up part of the circuit there's no need for any diodes in the new schematic?
The main reason for WP was not fear of overwriting the wrong chip but paranoia, However unlikely, insyde bioses are very vulnerable to modification and attack, I'd feel safe knowing the chip is write protected. *carefully buts his tinfoil hat back on*
Can I ask the purpose of the ceramic cap? Am I right in...Leave a comment:
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Re: Triple bios schematic/pcb design help
Thanks for the input stj, it is most valued.
My decision to use CS pin was based on work already done by [URL]http://blog.jacksoftlabs.com[/URL], i did wonder why he never chose to switch vcc.
what would be needed for an LED selection indicator given the board offering 3.3v on VCC, is there any protection circuitry you would add.
Frankly im looking for the simplest most compact design with a bit of functionality, i don't want to overcomplicate things.
"About the Dual-BIOS mod:...Leave a comment:
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Triple bios schematic/pcb design help
I've been trying to get my head around designing a triple bios pcb solution for bios modding/testing. Sorta like the dual bios backup found in most modern motherboards from gigabyte only this will be for laptop bios testing.
It will be directly soldered onto the SOIC/DIP pads of the motherboard controlled by a slide switch, have room for 3 custom bios eeproms, the third maybe a removable test socket. Possible selection LED's, Write protect dip switch, clear cmos button.
I need help and advice with the schematics from the community as im not great with pcb design.
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Re: Sapphire HD 7870 possible short
okay so I went ahead and tested TP101 -104 for you eekcage, heres what I get.
TP101 - 3.56
TP102 - 4.58
TP103 - 4.10
TP104 - 3.74
If you require anymore readings just ask, hope this helps.Leave a comment:
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Re: Sapphire HD 7870 possible short
Hi eekcage,
don't worry about the hijack, the more we can find out about these cards the better, like yourself I could barely find any technical / repair info on the net that's why I came here and asked the questions myself. Ill check TP101 for you in a bit and give you my reading.
Would you mind sharing your knowledge on the lanes / differential pair? Am I right in thinking TP101 stands for 'test point'? If we can map out all 'normal' test point readings on a working card it may well provide a source of reference...Leave a comment:
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Re: Sapphire HD 7870 possible short
Okay so Fairchild denied my request for a free sample not sure why? So I went ahead and ordered them from Mouser with some stupidly over priced delivery charge £12, so I order a few to make it worth my while. Why is the delivery from these chip companies so high? Even from my aliexpress account the Chinese where quoting something crazy to send something weighing next to nothing and costing pennies. I've ordered hundreds of capacitors and delivery was really cheap.
If someone could shed some light on that I'd appreciate it.
...Last edited by modman1337; 02-11-2014, 10:50 AM.Leave a comment:
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Re: Sapphire HD 7870 possible short
Nice thanks, I think I understand the circuit better now.
Right so I got my camera out again to try find out what these mosfets were and who manufactures them.
Heres what I got:-
FDC18AB
FDMF
6705B
Which I think translates to a Fairchild FDMF6705B 6x6 PQFN XS DRMOS FAMILY MOSFET, do you agree momaka?...Last edited by modman1337; 02-09-2014, 06:58 AM.Leave a comment:
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Re: Sapphire HD 7870 possible short
Thank you sir momaka to the rescue. I very much appreciate your help, that's a very in depth reply still trying to wrap my head around it.
So here's what I get:
Upper IR0 to ground - OL
Lower IRO to ground - 128 ohms
R19's to ground - 6.8 ohms
12v 6pin molex to ground measures 6.6 - 7 ohms
So does this mean it's an upper MOSFET at fault?
It's the whole upper / lower thing that I'm finding had to grasp. How would I find the right pair of mosfets. Sorry if...Leave a comment:
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Sapphire HD 7870 possible short
Hi folks,
I wanna start off by saying hi to all you guys as this is my first post, this is the only place I come to when in need of advise and knowledgeable answers. Great forum you all have here. I've been repairing my PC hardware for some time now (Minor cap replacement, Dc jacks). But that's kind of the extent of my knowledge so want to improve my skills and learn a bit more so what better way than to jump right it at the deep end and try fix a dead graphics card ay?
The card in question is a Sapphire 7870 Ghz edition 2GB which I believe sticks to amd's reference...
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