MS4X - DME write maximum count?

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MS4X - DME write maximum count?

Postby harlard » Thu Jul 09, 2020 5:04 pm

Hello all,

It has been a while since I have messed with flashing a factory engine management system. It would be great if you could bust or confirm this myth: is there a software-defined limit to the amount of partial/full writes allowed in a Siemens MS4X DME?

Thanks in advance,


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Re: MS4X - DME write maximum count?

Postby Renovelo » Thu Jul 09, 2020 7:35 pm

Contrary to what others on the internet may say, no DME in the MS4x family has a flash limit that tuners need to worry about. The EEPROMs themselves have a flash limit but they're far greater than any tuner will ever reach. For example, the AM29F400 in MS42 has a documented read/write limit of 1 million cycles. The EEPROMs could probably withstand more cycles than this, but the manufacturer only guarantees proper functionality for this many. We have flashed our bench DMEs probably hundreds of times since we first started working on ByteTuner.

With BMW DMEs, most people probably confuse true flash limits with the AIF limits. Factory flashing software writes an entry in the AIF region during each flash. There is a limit to how many times the AIF region can be written. Our software does not write to the AIF region at all, so there is no need to worry about this.

The only DME family in this era with true flash limits is MSS5x. However, ByteTuner allows you to reset these flash counters via OBD2 with a simple click of a button.

Myth busted!

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