The IBM PCjr was built by Teledyne for IBM.  IBM decided at the last minute to disable DMA so the computer could not compete with the IBM PC.  Terrible mistake.  The jr could not run spreadsheets so anyone who thought they could buy a jr and run spreadsheets at home was sadly mistaken.

Also IBM was known for its quality keyboard.  On the jr, they had a chicklet keyboard which as lousy.  To fix the problem, you could bring your chicklet keyboard to ComputerLand and they would give you a nice keyboard with real keys.  However, they never fixed the DMA problem which killed the sales.