I started a lot of debate when I wrote: The two rumours I had heard are thus: 1. The AT had been deliberately set up so that it couldn't make one of the transitions between modes - IBM were being paranoid and thinking of crackers having a back door - but this "feature" was removed in the PS/2. This is obviously a garbled version of the things you've all been telling me about 286s and the AT having to reset itself from time to time. Thank you for clearing this up. 2. Intel had a fault on a large batch of 286s that couldn't do some of the things you'd expect. IBM bought a job lot on the cheap and stuck them in XT286s. Can anyone tell me the origin of this latter rumour? Has it now been discredited? BTW What is Warp? Is it the OS/2 windowing system? If so, why would I want to use it at all, let alone on a 286? ;-) Philip. PS *** Off Topic *** I stand corrected. Uncle Roger is quite right about triangular manhole covers. However I don't know whether this still holds up (pun intended) if you have rounded corners and a thickness that is not negligible as well as the lip to support the cover in its normal position. I don't intend to try it to find out. Whoever posted that rather silly message about System/36 was right - this discussion has probably gone on too long. I will leave you with a thought: Make the cover a triangle, but with the sides arcs of circles centred on the opposite corner. (This works for any odd number of sides, like the 50p coin I mentioned earlier) P.