Looking for an 8 bit FDC...

Allison ajp166 at bellatlantic.net
Tue Oct 25 14:26:15 CDT 2005

>Subject: Re: Looking for an 8 bit FDC...
>   From: Jules Richardson <julesrichardsonuk at yahoo.co.uk>
>   Date: Tue, 25 Oct 2005 19:14:52 +0100
>     To: General Discussion: On-Topic and Off-Topic Posts <cctalk at classiccmp.org>
>Chuck Guzis wrote:
>>>Intel's 8271 looks like a possibility at the moment, but I thought I'd 
>>>poll the list for alternative ideas too. FM support is of course 
>>>critical - MFM is less of an issue as the host PC can handle that.
>> The 8271 is a pile of worms.  Don't even bother with it.
>> In a DIP package, if you want to restrict yourself to 5.25/3.5" MFM and FM
>> (but not HD) formats, the WD 1770/1772 is a nice compact (28 pin)  little
>I've certainly got 1770 chips lying around unused in the parts box... I 
>think you've just put that at the top of the list :)
>> Why a floppy to support your device, though?  There are many high-speed
>> interfaces available to choose from nowadays.  Why not feed your device via
>> USB?
>I'm interested in doing this in order to archive old floppies to modern 
>media, and out of the 5 or so PCs I can lay my hands on at home, none 
>are happy with FM data :-(
>Catweasel's ruled out on grounds of cost, lack of schematics, and the 
>fact that it's an internal board anyway.
>I need an external box of tricks so that I can easily use it to do 
>archival work both at home and at the museum (and potentially other 
>locations too). I know the museum PCs have serial and parallel ports, 
>but not all of them will have USB; plus I'm hoping to spend zero cash on 
>this and just use parts lying around at home - I'll have various serial 
>& parallel I/O chips but certainly no USB stuff!
>As an additional thought whilst writing this (admittedly not thought 
>through yet!) serial might be nicer than parallel so that at some future 
>date I can dump all of the necessary firmware onto the disk interface 
>box's ROM and in theory just talk to it using a comms package from the 
>PC host.
>Lots more work in terms of understanding the various download protocols 
>to do it that way, and it means that the disk interface box needs to 
>understand the resultant disk image format on the PC which I'm not sure 
>I like... but it does mean that all the host PC needs is a serial port 
>and some comms software (which is covered by pretty much any modern-ish 
>PC OS on the planet) rather than any special application to drive the box.
>If serial's the standard interface though it'd be zero hardware changes 
>to support this in the future - it just means being stuck with a slower 
>serial protocol for disk image transfer, when parallel would be faster. 
>And yeah, I think we've been over this on this list before... :-)

If you have an older box with ISA bus there is a direct solution..

Put a 1793/2793/1770 on a ISA protoboard and run it direct from the
PC.  Then all you need to write is software to make it go.  There's
absolutly no reason why you cannot do that.


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