Looking for an 8 bit FDC...
ajp166 at bellatlantic.net
Tue Oct 25 13:09:55 CDT 2005
>Subject: Re: Looking for an 8 bit FDC...
> From: Jules Richardson <julesrichardsonuk at yahoo.co.uk>
> Date: Tue, 25 Oct 2005 18:43:13 +0100
> To: General Discussion: On-Topic and Off-Topic Posts <cctalk at classiccmp.org>
>>>Subject: Looking for an 8 bit FDC...
>>> From: Jules Richardson <julesrichardsonuk at yahoo.co.uk>
>>> Date: Tue, 25 Oct 2005 17:28:35 +0100
>>> To: General Discussion: On-Topic and Off-Topic Posts <cctalk at classiccmp.org>
>>>OK, I'm wanting to build a board with an 8 bit CPU (probably Z80,
>>>possibly 6502) and a floppy controller IC on board with the intention of
>>>hanging it off my PC (via serial or parallel, undecided yet) and
>>>allowing me to read and write *most* formats from various 1980's 8 bit
>>>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.
>> ick poo.. The 8271 was not widely used especially on 8bitters. If your
>> serious then 1793 that was common as house flies and does most all soft
>Ahh, not had experience of that one before (I don't think anyway). 177x
>was pretty common in machines over here, and the 8271 gets used in a lot
>of Acorn hardware which is why I'm used to it...
the Acorn is one of the few that used it. The 8271 was rare here compared
to 1771 and 1793.
>> Seriously 32kbyte static ram chips are easy to get (JDR and other have them)
>> and EEprom (small is 2k and 8k are easy to find).
>Well part of the plan is to raid the junk pile and at least put some of
>it to use, which would likely mean a 2732 EPROM for on-board ROM and
>6116 SRAM chips for memory - latter subject to power requirements and
>board space though. I know I've got quite a few of them kicking around,
>but they're physically large chips and not *that* big a capacity (8kbit
>or 16kbit I think, going from my hazy memory...)
The 6116 is a great part and 4 of them are enough for a track level buffer
and another 2 would provide adaquate code space.
>Of course I've got a boatload of various DRAM chips though, so if the
>Z80 does provide pretty much all the refresh needed then maybe that's a
GO TO Gaby's site and look for Tim Olmstead DRAM article. It covers DRAM
interface in the context of Z80 systems and is very complete.
>> Another way to do this is a small S100 bus with 16k of ram, a rom card
>> Z80 cpu card and a serial board with one each of:
>> NS* MDSA-4(a common hard sector that one does SD and DD)
>> Tarbel 1771 based card (SD and really off 1771 specific formats)
>> CCS 1793 based soft sector card. (most all softsector formats)
>> Compupro 765 based card (why not!)
>Ahh, thanks for that list. We've got a truckload of S100 hardware at the
>museum, so there's definitely a possibility there - I'm just not sure
>without checking what FDC cards we have. I don't know what spare ROM
>boards we'll have either (my programmer won't do three-rail devices, so
>I'd need a board that'd take slightly newer EPROMs...)
Or enough eprom to boot over wire. Everytime I need a system to do xxzzy
I find enough peices in the S100 spares bin to build it with minimal fuss.
Simple enough, anything with WD1771 will do SD, 1791/93 does SD and DD
and there were some cards with 765 (Compupro) that do SD/DD.
The real key is documentation, however for the popular cards its wasy to
docs on line.
>> If you stick to static parts and 6502 or Z80 the whole thing should be
>> simple. Parallel port (bidirectional) will be faster but serial is easier
>> though slower.
>Agreed :) I can't see parallel being complex though; I guess there's
>just handshaking protocol to design on top of hooking the chip itself up
>(unless I got for individual ICs to do the parallel interface), but it
>doesn't need to be anything complicated.
It's really traffic management, who talks first and when. ;)
>I've got a few weeks until I'm back in the UK, so it gives me something
>to ponder over in the meantime though :)
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