new part-faulty RAM chips?

Does anyone know if the Sinclair Spectrum ever made use of RAM chips that were known to be part-faulty as-new? This was just asked over on another mailing list... I recall discussions about such chips in the past on here, where manufacturers would sell 'faulty' RAM to vendors at lower cost where only half of the address map could store data reliably. However, I'm sure that was late 70s or so, not the early 80s when the Spectrum existed; by then I would have thought that the manufacturers would have had the reliability issues sorted out and would simply dump faulty stock? Anyone able to confirm? cheers Jules -- If you've ever wondered how you get triangles from a cow You need buttermilk and cheese, and an equilateral chainsaw