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Konamiman / Nextor

A disk operating system for MSX computers, forked from MSX-DOS 2.31
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DEV_STATUS is called for current drive every time ENTER key is pressed on empty string #46

Closed Eugeny1 closed 4 years ago

Eugeny1 commented 4 years ago

If I press ENTER key at the empty prompt of the DOS A:> (enter) it queries drive A for disk change status, and then reads its structures if disk was changed. While it is very good to stay up to date even when nothing actually being done by user or any application, it causes problems with floppies. Original logic of the DSKCHG is when it is invoked, driver gives past/current status to the kernel and clears its internal flag so that next time DSKCHG is called and device is not changed driver gives information that device was not changed since last call. For floppies, to read the disk change bit, as well as to clear it internally in the FDD, it is required to start motor and perform a seek operation (see here https://wiki.osdev.org/Floppy#DIR_register.2C_Disk_Change_bit). Thus with current logic, on every spare ENTER key press there will be floppy drive motor on and possible seek operation - this wears the drive and floppy disk out.

Eugeny1 commented 4 years ago

In the private conversation Nestor said that this behavior is dependent on the SET PROMPT setting. If it is ON, then device is being queried, otherwise not. Thus behavior is confirmed to exist in MSX-DOS2 implementation, thus it is not a Nextor issue but rather than DOS2 architectural feature.