characterizing speed performance of floppy drive controller

So I’ve got things working rather swimmingly right now.  Switched drives from Samsung to Sony, and it’s made a huge difference.  The Sony just seems to work better.

I’m averaging about 355ms per track, yielding 57s total disk times.  The 355ms is made up of 313ms of transfer time at an effective throughput rate on the serial of around 1.175mbps.  Which is basically 1.5mbps baud rate, theoretical max of 1.2mbps.  This isn’t horrible performance, but I really want to get back to 2mbps.  I haven’t been using 2mbps because I have massive errors, but I think that there is some round off happening in my UART that prevents it from working correctly.  I need to revisit my UART code and find out exactly why 2mbps doesn’t work.  I’ve run this usb->ttl converter at 2mbps with my uC, so it really should work fine.

If I go to 2mbps, I’ll EASILY chop off the 88ms from 313ms, and I’ll be transferring the track to the PC in REAL TIME.  Basically, as fast as I receive it, I’ll be sending it to the PC.  Remember, that because I transmit the pulse times, and not the data, that fast times are really required.  This is a little more complicated than just saying the RAW MFM rate is 500kbps, so you need 500kbps of bandwidth to the PC.

There are several optimizations I can do, and I’ll post more later.

About the author


Amateur Electronics Design Engineer and Hacker

One Comment

  • Holy crap. I’ve got some partial progress on running this thing at 2mbps.

    Wow is it fast!@#

    I’m processing tracks including the read as fast as 247ms per track.

    That’s reading the entire disk in about 40 seconds.

    There’s some work to do still, but the progress is motivating!