Or have there been many redesigns of the chips since my WORKING in it in 89.

thanks

Andy
The DEBUG program included with Windows NT/2000/XP/2003 appears to operate the same as it did under DOS 5.0, but with two major exceptions:

1) DEBUG is no longer allowed to load from or write to any logical HDD sectors; only named files can still be read from or WRITTEN to under these OSs. HOWEVER, it can still access diskette sectors in the A:\ or B:\ drives with the L and W commands, but only if those diskettes contain a file system the OS can recognize.

DEBUG has never been able to directly access areas of an HDD outside of its DRIVE volumes; such as an Extended partition table or even the MBR sector.! However, DEBUG can be used to access such data by programming it to run INT13 commands or using a script file under DOS.

2) The I and O commands are essentially useless, since the program's interface with the REST of the system is only being emulated under these versions of Windows rather than having any direct access to the hardware. This was already true to varying degrees under previous versions of Windows.
Thanks Dias

Not that I'm into it anymore, but it was fun using it.