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mtx500
Joined: 21 Nov 2003
Posts: 117
Location: Nuremberg, Germany
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 Posted: Sun Apr 06, 2014 1:31 pm Post subject: |
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| Xsecret wrote: | | Is it possible to reinject a recompiled HyperCode into the AMIBIOS then flash and run successfully that modded BIOS ? If yes, I can try to tune some ASM code, but the space limitation is really a problem. |
Yes of course. But if you make a mistake, your NexGen won't boot anymore. Then you have to remove the BIOS chip and have to reprogram it outside of the motherboard.
It is much more convenient to install a second BIOS chip so that you can switch between them. One always holds the original content and the other is there for experimenting. Then, if it doesn't boot with the experimental BIOS, you just switch the BIOSses and can then boot again. You can always program the experimental BIOS in place. You only have to be careful with the switch 
Here is what I did:
You need an additional EEPROM chip SST PH29EE010, at least 150ns.
Also, routing the chip select line from the board to the switch and then back to the BIOS chips is not a good idea because it is long an unshielded and thus sensitive to noise. So you better place a logic gate in between: I used two OR gates from an 74ALS32.
Mechanical plan, side view:
| Code: |
____________
___| |___ 74ALS32
|____________|
____________________
_| |_ SST PH29EE010 (Experimental)
| |____________________| |
| ____________________ |
|_| |_| SST PH29EE010 (Original)
| |____________________| |
__|________________________|__
| | Socket, 32 pin
|______________________________|
] [ ] [
# #
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Circuit:
| Code: |
_______ Vdd
________ ________ /
_| |_| |_ /
__________| | 1 14 | |/_____________________
SW2 /|_| |_| |
| | | |
| _| |_ ____________ |
\| | 2 13 | |_____| 10K |___|
/|_| |_|\ |____________| |
| | | \_______ |
| _| |_ SW1 |
| | | 3 12 | |_________ |
| |_| |_| #CE input (Socket) |
| | | |
| _| 74xx32 |_ |
\| | 4 11 | |_________ |
/|_| |_| #CE output Exp. BIOS |
| | | |
| _| |_ ____________ |
\| | 5 10 | |_____| 10K |___|
/|_| |_|\ |____________|
| | | \_______
| _| |_ SW3
| | | 6 9 | |_________
| |_| |_| #CE input (Socket)
| | |
| _| |_
\| | 7 8 | |_________
/|_| |_| #CE output Orig, BIOS
/ |___________________|
_______/
Vss
Switch
Position "Original"
/\ ___________
\ \ | |_____ SW1
\ \| |
\ | |_____ SW2
\| |
| |_____ SW3
|___________|
Position "Experimental"
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See the attached picture. |
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xsecret
Joined: 01 Feb 2004
Posts: 1847
Location: France
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| Posted: Sun Apr 06, 2014 1:37 pm Post subject: |
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Nice trick  I love it !
But for this project, I have an USB Programmer (GALEP-5, really nice tool) and I will add a ZIF socket on the motherboard.
Could you describe which tool do you use to rebuild the AMI BIOS with the new HyperCode binary ? I used to be a BIOS Engineer in another life, but I only worked with Award BIOS.
_________________
ES-Only Collector : http://www.engineering-sample.com
Universal Chip Analyzer (UCA) : https://x86.fr/uca / http://www.cpu-world.com/forum/viewtopic.php?t=34349 |
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mtx500
Joined: 21 Nov 2003
Posts: 117
Location: Nuremberg, Germany
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| Posted: Tue Apr 08, 2014 4:17 pm Post subject: |
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| Xsecret wrote: | | Could you describe which tool do you use to rebuild the AMI BIOS with the new HyperCode binary ? |
There is no need to re-assemble or re-build the AMI BIOS itself. AMI BIOS and hypercode start at different, fixed offsets within the BIOS image, so you can just overwrite the hypercode without touching the AMI BIOS.
This ZIP contains the original hypercode binaries with their IDA Pro data base, the sources, and the makefile and the batch file to create and compare all versions of hypercode: http://www.memotech.franken.de/Temp/Hypercode.zip .
It uses Borland Assembler, Linker and Make.
For a VL BIOS, just insert the hypercode into the BIOS image at relative offset 0x4000.
For a PCI BIOS, you first have to compress the hypercode. You can use my PERL script HYPACK.PL, see http://www.memotech.franken.de/NexGen/Bios.html#Dissecting_the_BIOS_images_ . Then insert it into the BIOS image at relative offset 0x0000. |
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Jeff_HxC2001
Joined: 27 Jul 2014
Posts: 2
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| Posted: Sun Jul 27, 2014 3:59 am Post subject: |
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Hi,
I just found my old Nx586 P90 PCI board and this topic interest me a lot.
I use an eprom emulator to work on the BIOS. This is very handy and fast. 
@mtx500 : i have modified your software to be able to patch/change a module into the AMIBIOS rom file. i will publish it soon.
Question : Is there some documentations about the Northbridge chipset present on these motherboards ? |
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mavroxur
Joined: 06 Jul 2005
Posts: 1192
Location: Wichita Falls, TX
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| Posted: Sun Jul 27, 2014 11:43 am Post subject: |
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| Love the floppy emulator. |
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xsecret
Joined: 01 Feb 2004
Posts: 1847
Location: France
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mtx500
Joined: 21 Nov 2003
Posts: 117
Location: Nuremberg, Germany
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| Posted: Sun Jul 27, 2014 3:55 pm Post subject: |
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Thanks for sharing the pictures. This looks like heavy work. Great!
| Jeff_HxC2001 wrote: | | Question : Is there some documentations about the Northbridge chipset present on these motherboards ? |
All the NexGen databooks were written by Warthman Associates (http://www.warthman.com/). Go to "Projects", "AMD" and there you will find NxPC System Logic Data Book (or NxPC System Controller Databook, as it says on the top page).
Some years ago I contacted Mr. Warthman by e-mail and asked about a way to get a copy of this book. He kindly replied that his contract with NexGen does not allow him to give copies, but if I manage to find someone at AMD which gives an official allowance, he would be happy to provide a copy to me.
I did not succeed in getting the necessary contacts to AMD ...
But it is just difficult to find the right person in a big organisation if you are on another continent and it's not your native language. |
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Jeff_HxC2001
Joined: 27 Jul 2014
Posts: 2
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| Posted: Sun Jul 27, 2014 4:16 pm Post subject: |
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| mtx500 wrote: |
Some years ago I contacted Mr. Warthman by e-mail and asked about a way to get a copy of this book. He kindly replied that his contract with NexGen does not allow him to give copies, but if I manage to find someone at AMD which gives an official allowance, he would be happy to provide a copy to me.
I did not succeed in getting the necessary contacts to AMD ...
But it is just difficult to find the right person in a big organisation if you are on another continent and it's not your native language. |
yes i know these problems... i have some contacts name with the competitor, but very few with AMD.
Maybe that we should try to contact some devellopers... |
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thehinac
Joined: 08 Aug 2014
Posts: 14
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| Posted: Fri Aug 08, 2014 1:59 pm Post subject: Need help from nexgen owners on a rebuild project. |
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I have a rebuild project I'm working on with a VLB board version. I tossed the original fan like 5 years ago thinking I'll just get another not knowing how odd the fan is. So I was able to get a hold of an original fan and heatsink but no plastic clips that hold the sink to the chip. Could someone snap some photos and get me a few precision measurements? So I can make a 3d printable object.
how long the posts are, and how thick.
how thick the lip is that slides under the cpu.
the lengths to the tips of the sides.
how long is the threaded area of the posts.
And any other measurements would help, unless you have one to spare.
Any help would be wonderful. |
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