Burning BIOS to a new EEPROM

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Burning BIOS to a new EEPROM

Postby debs3759 » 2018-6-13 @ 17:53

I have two Asus PVI-486SP3 motherboard, rev 1.22 and rev 1.8

I'm told that the original BIOS chip on the 1.22 will not take the latest BIOS, but that a newer 128Kx8 EEPROM can be written and inserted in the board. Is it possible (and safe) to boot the system I built with the 1.8 board, replace the BIOS chip while running, then write the new BIOS to the target chip? If it is possible, what precautions do I need to take? Will I need to enable BIOS shadowing? That will save me the cost of asking someone with a burner to write it for me (or the cost of a cheap writer).

The 1.8 is in a working system, and the new chips are NOS. Obviously I want to avoid damaging either, so don't want to go the trial and error route :)
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Re: Burning BIOS to a new EEPROM

Postby Tiido » 2018-6-13 @ 18:46

That is called hotflashing and it is possible but care must be taken to make sure pins contact roughly at the same time. Stuff like pushing in one side and then other is a big no-no and can result in destruction of the chip and in worst case damage the motherboard too.
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Re: Burning BIOS to a new EEPROM

Postby Cga.8086 » 2018-6-13 @ 19:55

Suppose you buy one of those epromm flashers from ebay that come with a kit full of tools and things.
and over the years you were able to remove more than 10 bios chips from broken motherboards that were trashed.

is it easy to flash those chips?

you just remove the sticker, place them under a UV light bulb for a night and that erases it?

the flashing kit sold on ebay auto detects what type of epromm you just inserted?
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Re: Burning BIOS to a new EEPROM

Postby bjwil1991 » 2018-6-13 @ 20:00

Another thing to do would be to purchase spare chips in case you break them (my plan is to dump the BIOS content from my Packard Bell's motherboard and make 4 chips with the same content and keep 2 of them, and send 2 more to someone who needs them). When I buy chips or other DIY items online, I always get double the quantity in case I mess up with the soldering (which does happen), but my soldering skills are getting better.
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Re: Burning BIOS to a new EEPROM

Postby Tiido » 2018-6-13 @ 20:28

Cga.8086 wrote:Suppose you buy one of those epromm flashers from ebay that come with a kit full of tools and things.
and over the years you were able to remove more than 10 bios chips from broken motherboards that were trashed.

is it easy to flash those chips?

you just remove the sticker, place them under a UV light bulb for a night and that erases it?

the flashing kit sold on ebay auto detects what type of epromm you just inserted?


The ones with window on them are EPROMs and not flash chips (or EEPROMs, EEPROM refers to a small byte/word erasable serial device) and those cannot be programmed in system, you need a dedicated programmer for them. There are also windowless OTP EPROMs that you can identify with part number containing 27 rather than 28 or 29, those will also not be rewritable. 28 and 29, 39 and 49 are flash, 27 EPROM. 24 and 93 are for EEPROMs and those aren't useful for BIOS business, 25 is for serial flashes that most modern motherboards use.
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Re: Burning BIOS to a new EEPROM

Postby jesolo » 2018-6-13 @ 20:47

I would recommend to rather buy an E(E)PROM reader/burner, like the MiniPro TL866CS - they cost about $50.

Just take note that earlier revisions of the PVI-486SP3 motherboard sometimes used an earlier revision of the SIS 496/497 chipsets. These earlier chipset revisions are not compatible with the later BIOS versions - refer http://gboeger.de/Computer/Asus_PVI486SP3/pvisp3.html.

Also, some of these motherboards used a 12V EEPROM chip whereas some used a 5V EEPROM chip (only way to confirm is to peel back the sticker on the BIOS ROM chip and then configure the jumpers on the motherboard accordingly).
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Re: Burning BIOS to a new EEPROM

Postby bjwil1991 » 2018-6-13 @ 21:08

I have that particular device and I've backed up two EPROM chips: one for the S3 Virge/VX (STB Velocity 3D) video card and a SCSI PCI card that was pulled from a broken down Apple PowerMac G3 (kept the BIOS chip out and it gets detected in Windows surprisingly).

Also, go the device supported list link to check and see if the chips you're ordering can work with it as well. I checked the 4 chips I want to purchase to see if they're supported, and they are (thankfully).

So, basically, a chip like this one: https://www.digikey.com/product-detail/ ... ND/2297826 would suffice.

Check how many pins, access time (varies by motherboard, where 70ns is the fastest), and length between one pin to the one across (ex: 0.600" or 15.24mm).
Last edited by bjwil1991 on 2018-6-14 @ 13:25, edited 1 time in total.
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Re: Burning BIOS to a new EEPROM

Postby debs3759 » 2018-6-13 @ 22:29

bjwil1991 wrote:Another thing to do would be to purchase spare chips in case you break them (my plan is to dump the BIOS content from my Packard Bell's motherboard and make 4 chips with the same content and keep 2 of them, and send 2 more to someone who needs them). When I buy chips or other DIY items online, I always get double the quantity in case I mess up with the soldering (which does happen), but my soldering skills are getting better.


They are socketed chips, so soldering isn't an issue. I only need one, so bought two in case I mess something up.
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Re: Burning BIOS to a new EEPROM

Postby debs3759 » 2018-6-13 @ 22:35

jesolo wrote:I would recommend to rather buy an E(E)PROM reader/burner, like the MiniPro TL866CS - they cost about $50.

Just take note that earlier revisions of the PVI-486SP3 motherboard sometimes used an earlier revision of the SIS 496/497 chipsets. These earlier chipset revisions are not compatible with the later BIOS versions - refer http://gboeger.de/Computer/Asus_PVI486SP3/pvisp3.html.

Also, some of these motherboards used a 12V EEPROM chip whereas some used a 5V EEPROM chip (only way to confirm is to peel back the sticker on the BIOS ROM chip and then configure the jumpers on the motherboard accordingly).


I am considering buying the TL866CS. Got one in my eBay watch list.

Thanks for the link. I used that page for CPU type jumper setting, but hadn't looked at what other info they have. According to that site, the 1.22 and 1.8 are the same stepping, despite the chips on the 1.22 having date codes that are a year earlier.
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Re: Burning BIOS to a new EEPROM

Postby debs3759 » 2018-6-13 @ 22:46

bjwil1991 wrote:Also, go the device supported list link to check and see if the chips you're ordering can work with it as well. I checked the 4 chips I want to purchase to see if they're supported, and they are (thankfully).


Thank you, that is very useful.

So, basically, a chip like this one: https://www.digikey.com/scripts/DkSearc ... 2133482179 would suffice.


That link goes to an index page.
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Re: Burning BIOS to a new EEPROM

Postby bjwil1991 » 2018-6-14 @ 13:26

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Re: Burning BIOS to a new EEPROM

Postby dionb » 2018-6-14 @ 13:43

Tiido wrote:That is called hotflashing and it is possible but care must be taken to make sure pins contact roughly at the same time. Stuff like pushing in one side and then other is a big no-no and can result in destruction of the chip and in worst case damage the motherboard too.

Er, no.

The only risks are due to incorrect orientation (wrong way round or pins in wrong hole) or shorting something else by clumsiness. So long as you put the right pin (and only the right pin) in the correct hole in the socket, it doesn't matter at all which goes in first or what order follows.

I've been hotflashing regularly for the better part of 15 years now and only once damaged a board or EEPROM. That was the time I put it in the wrong way round - *don't* do that. Rest assured I an a very clumsy human and the other times were by no means picture-perfect - particularly as you get sloppy once you know it doesn't really matter (er, and I have at least a few times done it while significantly drunk).

If you have an EEPROM burner, use that. If you have a PCI/ISA card you can flash to instead of to the BIOS socket, use that. But if you don't have any of that, hotflashing is a decent option, with real, but very manageable, risks.
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Re: Burning BIOS to a new EEPROM

Postby Tiido » 2018-6-14 @ 14:07

Latchup is a real thing (and can and will happen if ground isn't gonnected) and also IO pins will become power pins through the ESD protection diodes putting unnecessarily high current requirements on the IO drivers of the motherboards during that time if VCC isn't getting connected.
Reverse orientation is usually destructive as VCC and GND get swapped and boards that supply 12VPP also will make sure the chip dies. If you're unlucky that 12VPP finds its way through the ESD protection diodes into IO pins and then to the chipset frying parts of the motherboard too.
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Re: Burning BIOS to a new EEPROM

Postby bjwil1991 » 2018-6-14 @ 14:23

The one thing about the BIOS chips when people install them would insert them the wrong way.

General rule of thumb: follow the notch on both the socket and the chip to make sure they're parallel to each other. Learnt that the hard way when I accidentally reversed the L2 cache (one of them) and turned it on (got hot, but a small amount of smoke, but nothing major). Going to replace the sockets to be on the safe side, but the resistance is working.

Also depends on the system's voltage requirements for the chip itself:

jesolo wrote:Also, some of these motherboards used a 12V EEPROM chip whereas some used a 5V EEPROM chip (only way to confirm is to peel back the sticker on the BIOS ROM chip and then configure the jumpers on the motherboard accordingly).


I checked the documentation about the BIOS chip that's in my Packard Bell Pack-Mate 28 Plus in comparison to the chip I found on Digikey to see what the difference is, and both are 5V +/- 10% Vcc (4.5V-5.5V).

Documentation on the Intel 28F001BX-T: http://pdf.datasheetcatalog.com/datashe ... Xuvtyr.pdf

Documentation on the Micro Chip SST39SF010A-70: http://ww1.microchip.com/downloads/en/D ... 05022C.pdf
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Re: Burning BIOS to a new EEPROM

Postby Tiido » 2018-6-14 @ 15:48

The intel chip uses 12V programming voltage while the other part is 5V only
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Re: Burning BIOS to a new EEPROM

Postby bjwil1991 » 2018-6-14 @ 16:15

Forgot to look at that. Looks like I have to purchase the chips on eBay. Fortunately, my programmer and software will work with the chip according to the list I posted on here.
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Re: Burning BIOS to a new EEPROM

Postby debs3759 » 2018-6-14 @ 23:18

Thanks everyone. I will hotflash it when the chips arrive. Just bought 5 (better to have and not need, etc) from digikey, as they are faster and cheaper than what I found on eBay. Will have to take a look what else they've got to make shipping to the UK more cost effective :)
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