In 1983, Compaq introduced its first product, a portable computer weighing 28 pounds; 128-640K RAM, two 5.25" floppy drives, 9" monochrome CRT for $3590. It was extremely successful in the market, and the company took off like a rocket; the later Plus model added an internal hard drive.
In 1984, IBM released the Portable Personal Computer 5155 model 68, a similar design weighing 30 pounds; 256-512K or 640K RAM, one or two 5.25" floppy drives, 9" monochrome CRT. Wikipedia says it was cheaper, but doesn't give a number. http://oldcomputers.net/ibm5155.html on the contrary says $4225. By all accounts it did not sell well, was considered something of a flop and discontinued relatively early.
I personally have never seen the attraction of a 'portable' that weighs more than many desktop machines, but my feelings on the matter are immaterial; the fact is that the market at the time was hungry for such machines, and the Compaq sold very well.
Which makes it surprising that the IBM portable PC flopped; it looks to me like essentially the same product, only with the IBM nameplate; I would expect this to be an attractive proposition for the business computing market in the eighties.
So why is it that the Compaq portable sold well but the IBM didn't?