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Old 06-06-2019, 05:26 PM
oldskewel oldskewel is offline
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For anyone who can explain what "DME Ram" is, etc. I'm curious to learn more about what that means.

Back in the olden days when I would work on control systems etc., it would be common to have stuff that never changed stored in ROM. Truly fixed. Never changed. Then you'd have higher level stuff, like your control program, stored in EEPROM, for example. Then you'd have a processor that would boot using the ROM, load the EEPROM contents into its RAM, and run, using the rest of the available RAM while it's running.

The EEPROM was static unless there was an algorithm update (programming change). The RAM was volatile / dynamic / lost whenever powering down.

Do these DME systems work similarly?

Is the DME RAM really nonvolatile? And if it's volatile, is this like formatting vs. programming?

Is this DME RAM Backup actually a "reset" / "restore" or some similar word, vs. being a backup?

Is there really just one version of the DME firmware, e.g., that comes with the INPA programming software, vs. having each car having a different program based on year/month, options, etc.?

Personally, I would be very cautious about touching the firmware if that's what this is doing.

The DME in my 1985 911 has never been touched and is running fine (simpler days).

I recently, for the first time, did a very minor EEPROM programming to fix the temperature gauge in my 2001 3.0i, and was extremely cautious before making those changes. Maybe it was paranoia, but I did not want to brick my car. One particular thing that concerned me while doing that was that the 3 different examples I found all had different interstitial values between the ones that actually mattered. Never got an answer to that other than to leave them untouched, which worked.

https://xoutpost.com/1163366-post50.html

Trying to find answers to my questions above prior to posting this, I came across a guy whose eventual solution following a DME Ram reset was to strip his car for parts. Seriously.

Last summer, when I had my engine all apart, taking my sweet time with the battery disconnected for about 2 months, I had no problems at all when re-starting. I'd be more concerned about a voltage spike during the reconnection (battery spark) vs. concern for memory corruption over a period of weeks or months.
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2001 X5 3.0i, 203k miles, AT, owned since 2014
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