Ultimate FDC? (Was: IBM 6360 - Filesystem(ish) info?

Fred Cisin cisin at xenosoft.com
Tue Feb 19 18:25:08 CST 2019

On Tue, 19 Feb 2019, dwight wrote:
> Actually, I'd like to see it just read/write flux changes + index marks 
> onto a SD card for later analysis. Building all the smarts into the 
> controller means that some formats will get missed. One can later write 
> translation code for what ever format one has. Make this information 
> open source, much of it is already in bits and pieces. Make sure it can 
> read and buffer an entire track of data in RAM ( Gotek can't ).

As I see it, flux transition hardware COULD be all that is needed for 
hardware.  Emulation of FDC could be done in software with flux transition 

First stage would be with minimal software, to save the track flux 
transitions in a file.

Next stage, If and when a 765 FDC can be emulated.
THEN, make the FDC emulation code loadable into RAM, and repoint the 
Int13h vector to it. (TSR)
THEN, make new version that adds TRACK-READ (ala WD, NOT the multi-sector 
read in the 765)
Then fine details, such as whether or not to implement (switchable) index 
pulse "flash blindness", inability to handle 128 byte sectors, etc.
OR, that much could be done without full flux transition functions.

But, if you DO retain full access to the flux transition data, 
THEN, add GCR decoding, and add that into the FDC emulation (so that 
Int13h/fn2 could read GCR sectors, etc.)
THEN, add hard sector handling

THEN create IFS (Installable File System), which is totally not connected 
with any of this, except when needed for non 765 compatible physical 
formats. That is what XenoCopy would have eventually become, IFF I were to 
have been able to continue.
(Uniform did implement most of an installable file system for CP/M 

The end-user wants to load their Epson QX-10 documents and Kaypro CP/M 
documents into Word.  They don't want to know how it is done, nor go 
through the essential steps of reading alien sectors, processing alien 
file system to select appropriate sectors, AND convert word processor 
formatting codes from one word processor to another.  Do you think that 
you could teach them how?  XenoCopy transferred FILES; but left the 
content alone.  So, YES, I did get people telling me that XenoCopy had 
"trashed the last letter of every word in the Wordstar files"
I drew the line between transferring files V modification of the content 
of the files.  You are drawing the line between flux transition data V 
sectors/file system/files/content

Grumpy Ol' Fred     		cisin at xenosoft.com

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