… which memory chip quality levels exist and are available on the market?

We are asked frequently, which types of memory chips are used on eXceleram memory modules. We do not want to elaborate this too much, as we don’t want to disclose all secrets. But some answers can be given, nevertheless.

When producing memory chips the manufacturers want to have the highest possible ‘yield’, to be able to sell as much goods 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. So different quality levels are generated:

1. ‘Major Brand’ – fully tested chips, fulfilling all given specifications, and labelled by the maker with own brand name. These are e.g. chips of brand names Elpida, Hynix, Micron, Nanya, or Samsung (alphabetically listed, no ranking intended). The manufacturer tests finished memory modules further. Naturally this is the most expensive solution to get good memory modules.
2. ‘eTT’ – fully tested chips as well, but overproduced goods. 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.
3. ‘uTT’ – 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’.
4. ‘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.

 

eXceleram principally uses only ‘Major Brand’ and ‘eTT’ memory, and executes all module level tests that signify the difference between these two quality levels of memory. During selection tests there are similar harsh conditions as in ‘Major Brand’ production. ‘Downgraded’ modules are explicitly not used.

These are our main quality criteria: Use of good raw memory, not a single module leaves our house without being tested, and every memory module has to fulfil not only nominal specifications, but is tested to ‘overachieve’. In our opinion this is the only valid method to guarantee, that specifications can be fulfilled completely, even after several years of use.

Source: Exceleram 2011 - All information without guarantee