Oh, I know.
That would work in most cases (using the Superdrive to read 400k floppies) we tried that, but about half the disks wouldn't read, but with an 800k drive it did read some cleanly. Unfortunately the guy who was using his Mac II with an 800k drive had a hard drive crash, so he sent the disks to me for recovery.
So there are physical differences between 400k/800k drives and 1.44M drives that may make a big difference here.
For one thing, if the original drive used to write these was even slightly misaligned, the smaller r/w head in the 1.44M drive wouldn't see the whole band, but while the 400k head would see a bit more of it.
Also, the 400k drive uses a variable speed motor - so some tracks are read at different speeds than others in order to store more data. The 1.44M drives don't vary the motor speed, but rather vary the shift register clock rate that's used to read from the drive head.
I've actually had great luck moving data between a 1.44.M drive to a 400k drive. i.e. from a 7100 or a TAM, or a IIsi to a Lisa and back without any problems, but this is for disks that are 20 years old and have been stored in a non-controller environment (i.e. garage)
So that's why I'm trying to connect a 400k external drive to a IIsi, but wanted to check if I'm risking the IIsi's SWIM chip or other electronics.
I don't want to damage my poor IIsi in the process.
That would work in most cases (using the Superdrive to read 400k floppies) we tried that, but about half the disks wouldn't read, but with an 800k drive it did read some cleanly. Unfortunately the guy who was using his Mac II with an 800k drive had a hard drive crash, so he sent the disks to me for recovery.
So there are physical differences between 400k/800k drives and 1.44M drives that may make a big difference here.
For one thing, if the original drive used to write these was even slightly misaligned, the smaller r/w head in the 1.44M drive wouldn't see the whole band, but while the 400k head would see a bit more of it.
Also, the 400k drive uses a variable speed motor - so some tracks are read at different speeds than others in order to store more data. The 1.44M drives don't vary the motor speed, but rather vary the shift register clock rate that's used to read from the drive head.
I've actually had great luck moving data between a 1.44.M drive to a 400k drive. i.e. from a 7100 or a TAM, or a IIsi to a Lisa and back without any problems, but this is for disks that are 20 years old and have been stored in a non-controller environment (i.e. garage)
So that's why I'm trying to connect a 400k external drive to a IIsi, but wanted to check if I'm risking the IIsi's SWIM chip or other electronics.
I don't want to damage my poor IIsi in the process.