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SWTPC Floppy Disk/FLEX

antiquekid3

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So what is this whole FLEX thing about? Do I have to have it to operate a floppy disk? Or is it just another operating system that is used with a floppy disk?

I'd like to have some non-volatile memory in my SWTPC (it's annoying to keep having to load BASIC every time I turn on the computer!) but I'm not sure the best way to do that.

I do have some lithium-battery-topped 2K RAMs, but they are pretty old; I haven't a clue if the batteries are still any good...

Is there a floppy drive that doesn't require a controller, but rather just address inputs and data in/outs? That would be a very clever approach to non-volatile memory in older computers.

Kyle
 

Chuck(G)

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FLEX is an operating system for 6800/6809 written by TSC. You can find more information here.

If you need a lot of storage, Compact Flash (CF) has a very simple interface (basically 8-bit PATA). If you just need a few K or hundred K, consider Ramtron's FRAM Works just like SRAM, but is nonvolatile.

If you want to use floppies, an eBay seller was selling MicroSolutions Backpack floppy drives for $5 the each some time ago. The interface is simple--basically 8-bit out, 4 bit in. Not well documented, but I have my own notes on how it works.

There are other options...
 

antiquekid3

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I am really liking the idea of FRAM. I found the 64K version for $5 on Mouser. Too bad I just bought a 32K SRAM from Digi-Key yesterday to build my own 32K RAM card!

Maybe I'll get the FRAM, build a 64K card, have a switch that switches between the first and second 32K locations, and that way I can have twice as much non-volatile memory!

I read on the MicroSolutions Backpack 3.5" drive box on eBay that they also make (or made, I guess) a 5.25" drive. Do you think there's any chance of finding one of those around here?

Kyle
 

Chuck(G)

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I read on the MicroSolutions Backpack 3.5" drive box on eBay that they also make (or made, I guess) a 5.25" drive. Do you think there's any chance of finding one of those around here?

They were pretty uncommon even while they were in production. Still, 5.25" drive support is in the 3.5" version; you'll just have to work out the enclosure and power supply for it.

A little known tidbit is that the Backpack itself supports 2 drives (you could probably even rig it to support 4, since it uses an NS8477 FDC chip. It has a small serial NVRAM to hold configuration information and there are 4 slots for drive information in it.

I had to get all of this by reverse-engineering the driver software; MS refused to play ball with us when we asked for interface information, even though we were buying caselots of the drives. I eventually worked out a couple of drivers (DOS and Win9x) of our own for handling non-PC diskette formats.

I like FRAM; I wish Ramtron had a wider selection of devices, though.
 

NobodyIsHere

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Dec 21, 2006
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Hi! If you are interested in 6809 operating systems like FLEX you might want to check out the N8VEM 6809 host processor. The SWTPC is a sweet system but they aren't exactly common these days!

One the N8VEM builders is porting CUBIX to the 6809 host processor at the moment and has it running at least partially. That effort is laying the foundation for future 6809 operating systems such as FLEX. CUBIX support will include floppy disk, IDE, and ATAPI support. I believe it will run with video support in addition to serial interface.

The N8VEM 6809 host processor uses the Z80 SBC as its IO processor so the software that runs on the Z80 could probably be adapted to FLEX. I realize this is not exactly what you were asking about but if you or others were interested in 6809 operating systems this would provide an entry point without requiring expensive and/or hard to find legacy systems.

I believe FLEX could be ported to the 6809 host processor and probably will be eventually. The CUBIX port will help a lot since it will build up the Z80 side IO servicing routines. Once I complete the IO mezzanine board to give the 6809 host processor its own IO and bus interfaces it will be easier too.

Thanks and have a nice day!

Andrew Lynch
 
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