AT&T 7300

I don't see how switching from a 1010 to a 2010 will help with the number of heads in a controller => drive interface. Both chips have three bits to define the head address. One thing that could be done with the external SDH register, however, is encode a drive select bit as a head address. However, the hardware to do that would already have to be in place. Most controllers did it the long slow way, using an external device to generate the head and drive select signals. I used several different drives with more than eight heads, using the drive select in at least one case. It's merely a matter of lying to the device with its bit defiitions. However, the track and sector ID fields will have a seemingly wrong head address if the fact that a mapping trick is in place isn't taken into account in the formatting routine. Any checks of the contents of the head field in the SDH register will reflect what the chip knows is the correct number of heads as it has read it from the drive's sector ID field, and the driver software has to compensate for that. If you're in a position to use that signal as a partitioning vehicle, you're that much ahead of the game. The user and the OS will understand much more easily if a physical drive change occurs when a drive change is signalled in the SDH address. Dick ----- Original Message ----- From: Neil Cherry <ncherry(a)home.net> To: <classiccmp(a)classiccmp.org> Sent: Saturday, October 28, 2000 9:58 PM Subject: Re: AT&T 7300 head.