IBMMuseum
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- Aug 28, 2006
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IBM sold ESDI and DBA disks in the PS/2
The 3.5" drives with a single large edge connector like in the 50z are not ESDI, they are DBA
The true ESDI controllers (https://www.ardent-tool.com/storage/ESDI.html) and (5-1/4") drives are for the PS/2 Model 60 and 80 (towers). "DBA-ESDI" is mixing up some circuitry of the controller and (3-1/2") drives from the 60/80 design (same electronics are there, but as you have stated, the connection became largely proprietary). DBA-ESDI started with the same 8031 microcontroller as the IBM 60/80 ESDI, but later changed to the 80C196Kx; Here is a page I developed to show the response to INT 13h, Function 1Ch, Subfunction 0Bh, an 'ESDI' ROM BIOS call: https://ibmmuseum.com/Interrupts/INT13h/INT13h1C0B.htm