Memory size of the STM32F10xx Medium-density with Device ID:0x410 exceeding 64KBytes?

[Bvan.8]

When using the ST-LINK Utility, after connecting to the target , I see :

Device ID:0x410

Device flash Size:64KBytes

Device family:STM32F10xx Medium-density

Chip marking is STM32F103R8T6

Flashing a software package of 128KBytes seems to work! Verify after programming shows no error. Even after reading back the package I notice the memory size = 0x1FFFC (about 128K) and content seems intact. The aplication is running (including ROM memory check)!

Does the device have more than 64KBytes memory ??

[waclawek.jan]

It's the same physical chip as the one with the bigger FLASH; however, that FLASH is not tested at factory and is not guaranteed to work.

That you casually find it working means nothing, it may stop working at different temperatures/supply voltages etc.

JW

[Danish1]

It can happen, but you shouldn't rely on it.

ST probably only make parts in a few FLASH sizes. But it is possible for a speck of dirt to land on a chip during manufacture making some of the FLASH to be bad. Rather than scrap that chip, they probably re-map the FLASH so they are sure there is good FLASH where the data sheet says there is. And sell that part as a small-FLASH part.

It might be that the "bad" FLASH is largely good (i.e. it programs properly first time) but on test they find it doesn't have the safety-margin that ST are looking for, so they don't feel they can guarantee the number of programming cycles and data-retention shown in the data sheet. Or it might be that a particular FLASH cell or bit is stuck either high or low.

If the yield on the parts is good and there is great demand for the small-FLASH parts, ST might decide to make a new mask-set with less FLASH resulting in smaller chip size hence many more chips per wafer. This is cheaper to make per chip, so ST can make more profit and/or sell at a lower price.