When producing memory chips, the manufacturers want to have the highest ‘yield’, to be able to sell as much as possible, and to have the least number of rejects. To achieve that goal, the ‘raw’ memory chips are tested in various stages of the production process, even before final mounting to memory modules – what complies with the manufacturer’s requirements, will be processed further. For maximizing earnings the chip makers produce way more chips than they are able to test fully. Then different quality levels are generated:
‘eTT’(effective TesTed) – fully tested chips as well, but overproduced goods or the module manufacturers request is a "blank" chip to add maybe a customer logo. These are sold unlabeled, mounted to modules by other producers, and sold by them. Different to ‘Major Brand’, memory tests in finished module state are only rudimentary, or sometimes even omitted by these makers. Quality-wise these modules are comparable with ‘Major Brand’ ones, but they are a bit less expensive than the ones listed above. We now one chip manufacture he do, right now, not offer Major Brand Chips - PSC/Mira.
‘uTT’(unTesTed) – chips that nominally fulfill requirements, but were not subjected to the full set of tests. Usually these are fully functional as well, but that is not warranted. These chips are significantly cheaper than ‘Major Brand’ or ‘eTT’.
‘Downgraded’ – These are chips failing some critical tests, but most times work well under normal circumstances, as the chip makers' test criteria are usually harsher than expected real-life working conditions – to have ageing and variation reserves. These are the cheapest memory chips on market.
Source: Exceleram 2015 - All information without guarantee