> some less-than-perfect bus signals They are also responsible for some mysterious memory compatibility problems in PCs. All PC builders have this experience -

> some less-than-perfect bus signals They are also responsible for some mysterious memory compatibility problems in PCs. All PC builders have this experience - on a certain motherboard model, some DIMMs work, some doesn't, but they are all off-the-shelf parts that follow JEDEC standards. Often there are minor variations in electrical characteristics from DIMMs to DIMMs. If the signal integrity on the motherboard is marginal, there will be mysterious problems.