suipaste
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Joined: Tue Jul 17, 2012 6:50 pm

BBC Micro model B floppy drive

Tue Jul 17, 2012 7:44 pm

Hi I've been lurking around the site for a while now waiting for stocks of the Pi to because available. However during my wait I decided to see where it all began and a couple of days ago I acquired a BBC model B and figured this would be one of the best forums to pose questions because it's very active and I imagine there are a fair few BBC veterans kicking about so here goes.

Basically I got this BBC B off my Granddad. The machine runs like a dream, the only problem is the 5.25" duel floppy drive he gave me does not. Therefore I have no way of loading or saving programs onto the computer.

I found a couple of 3.5" floppy drives in the loft from some old computers and I was looking for some help connecting them to the BBC. In essence I think it's quite simple but I need a hand picking out the right parts to order as I have no idea about electronics. I plan on using the BBC's auxiliary power output socket to power the drives and then connect them with ribbon cable.

So my question is- if I were to buy the parts from http://uk.farnell.com/ what would go on my shopping list? The array of ribbon cables baffled me and I'm not sure what connector would fit the aux output (assuming you can even buy one these days)

Also is there any tweaking I would need to do to the drives themselves? From what I've read they should work fine but each one is missing a pin on the ribbon input on the bottom row first from the left I'm guessing this is normal for PCs but do I need to add a pin to get them to work with the BBC?

Thanks for your help.

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Mortimer
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Re: BBC Micro model B floppy drive

Tue Jul 17, 2012 8:06 pm

The BBC micros didn't support the 3.5" floppy drives commonly found in PCs as far as I know. If it ever worked that way, it would most likely have been through the use of a third party add-on. Whether or not you'd find something like that nowadays I don't know!
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The purpose of a little toe is to ensure you keep your furniture in the right place.

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rpdom
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Re: BBC Micro model B floppy drive

Tue Jul 17, 2012 8:10 pm

Oh cripes, it's been a long time since I did this and all my BBCs are long gone.

Not all PC floppy drives will work on a Beeb.

The missing pin isn't important.

It's easier to power the drive from a 5v PSU than try and find a connector for the Beeb's PSU (having said that, I might have one somewhere... I'll check it out tomorrow).

If you are using a PC floppy cable, then I think you need one with a twist (some of the wires crossed over) in it and connect the floppy to the drive B: connector. For some reason PC drive signalling works so drive 0 is B: and drive 1 is A:

I may be wrong about some or all of this. I welcome corrections.

As I said, I have used a PC 3.5" floppy drive on a BBC B to read and write ADFS disks successfully (DFS *might* work, but probably not and isn't advisable).

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Mortimer
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Re: BBC Micro model B floppy drive

Tue Jul 17, 2012 8:18 pm

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The purpose of a little toe is to ensure you keep your furniture in the right place.

suipaste
Posts: 17
Joined: Tue Jul 17, 2012 6:50 pm

Re: BBC Micro model B floppy drive

Tue Jul 17, 2012 9:00 pm

So from looking at all that it is in theory possible to connect them up and get them working but It's not just a simple case of connecting the power and ribbon cables together which sadly means it's probably beyond my ability.

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DexOS
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Re: BBC Micro model B floppy drive

Thu Jul 19, 2012 5:31 pm

Batteries not included, Some assembly required.

flaxcottage
Posts: 5
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Re: BBC Micro model B floppy drive

Tue Sep 18, 2012 9:22 pm

This is a very simple thing to do but only on BBC micros with the 1770DFS upgrade or on BBC Master computers;

1. obtain a 34-way grey ribbon cable (with the red wire along one edge)
2. obtain 2 x 34-way IDC header sockets
3. connect the ribbon cable to the sockets with the red wire to the connector for pin 1
4. before making the connection to the IDC header socket which will connect to the disk drive, carefully separate wires 10, 11 and 12 (keep them connected together but separated from the rest of the cable). Twist the wires 10, 11 and 12 so that wire 12 is in pin 10 position and wire 10 is in pin 12 position. Now crimp the cable into the connector.

Connect the drive to the cable (drives vary on which way round the plug will go). Connect a power lead to the drive. Plug the other end of the 34-way cable into the BBC disc drive socket, connect power to the drive, switch on the micro and hey presto a 3.5" drive acting as drive 0. This worked with a spare Teac drive I had.

Without twisting wires 10, 11 and 12, the drive will work as drive 1.

PC disk drive cables do not work without modification as they twist more than these three wires but it is quite easy to undo the plug, remove the wires, twist only the three and remake the plug again.

In theory two 34-way connectors, the end one twisted as above on the same ribbon cable will operate two 3.5" disk drives but I have not tried this yet.
Running Raspbian Linux or RISCOS 5 on 16Gb micro SD
Pi case a modified micro-ITX with 120W PSU. 4 port powered USB hub

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