Upon further inspection, I cannot find any reference to the SERVICE_MODE jumper on Dell's website, only the two you mentioned, RTCRST and PSWD.
It appears it may only be present on the mid tower form factor model of the Dell OptiPlex 7010, on which, it is directly under the PCI-e x16 (wired as x4) slot, to the left of INT_USB. A photo with the jumper circled in yellow has been made available for clarity here: https://imgur.com/a/Bn0yuin
I heard from a post on a public forum (https://www.bios-mods.com/forum/Thread-PSA-Dell-Service-Mode-jumper-on-Optiplex-machines
) that the service mode jumper would allow you to use an "auxiliary BIOS" in case the "BIOS flash" (assumed they meant the chip with the firmware on it) was damaged, however, after Jeremy's comment on the matter, I believe either that post was incorrect, or the "auxiliary" BIOS is on a different region of the same chip.
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On 12/29/18 4:47 PM, Jeremy Jackson wrote:
> On 2018-12-29 10:39 a.m., Kumonie Williams wrote:
Hi Kumonie, Jeremy,
adding Paul and Lynxis to CC as they were initial contributors of change
> Though, I do have a question I was hoping you'd be able to answer:
> The Dell OptiPlex 7010 has a service mode jumper, and, from my
> understanding, two ROM chips for two firmware images, the primary
> one used when the service mode jumper is not set, and the secondary
> one used when the service mode jumper has been set, with an
> immutable firmware image. My question is, given I only have one PC
> at the moment, my OptiPlex 7010, if I, say, flash a coreboot image
> that won't boot, would it be possible for me to simply set the
> service mode jumper from that point to safely use the second ROM
> chip? If so, it would make testing much easier.
> FYI, I have a 7010 that I bricked doing a Dell firmware update.
> The jumper didn't help me recover (yet?). I have one other that
> updated successfully.
I'm not sure about what jumper you talking. There are 2 close to BIOS
chips RTCRST and PSWD - neither would help directly in recover form bric
I took a picture of 2 chips . First seems to be SPI which
contain BIOS and second I would say is storage for Dell bloatware that
can run various hardware tests and display useless messages . I
will insepct SOIC8 later today, but SOIC16 requires special clip which
I don't have at this point.
@Paul,Lynxis, if you flashed anything on those devices please let me
know if there is any special treatment.
Apparently  seems to be MX25L3206E  - which is well supported by
flashrom. Second seems to MX25L6406E  - I wonder how much of that
we will need - it would be great to have additional 8MB of space.
I hope to take a look at it today night - will let you know about the
Embedded Systems Consultant
https://3mdeb.com | @3mdeb_com
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