I'm restoring some old SUN computers and they have ST combined SRAM, battery and clock chips in them (M48T59Y-70PC1). I've found the datasheets for the chips, but the replacements chips that I have purchased are M48T59Y-70PC1U and M48T59Y-70PC1D. Though I can't find any explanation anywhere for what the D or U stands for. Does anyone know ?
Also, apologies if I have posted this in the wrong section.