Looking for an 8 bit FDC...

Joe R. rigdonj at cfl.rr.com
Tue Oct 25 16:32:42 CDT 2005


At 03:26 PM 10/25/05 -0400, you wrote:
>>
>>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?
>>
>>Rationale:
>>
>>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... :-)
>>
>>cheers
>>
>>Jules
>
>
>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.
>
>Allison

  I have a used ISA Proto board that I'll contribute to the effort.

    Joe




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