XTIDE is an open source IDE disk controller for old XT computers that only have 8bit ISA expansion slots. The Vintage Computer Forum designed this controller so their retro gear could keep rolling with modern IDE storage like harddrives and compact flash cards.
Most of the ICs are simple 7400 series logic chips. They cut the 16bit IDE bus into 8bit nibbles chunks the older expansion slot can deal with. A parallel EEPROM (labeled SEEQ in this image) holds a bios that tells the computer how to use the board.
We’re looking for an old XT computer now, just so we can build one of these boards.
Since when is a nibble equal to eight bits? Maybe my age is getting the better of me but I seem to recall a nibble being four bits.
I used it as a generic reference to half-a-word, in this case 16bits, but it could very well be wrong!
I am so totally wrong:
http://en.wikipedia.org/wiki/Nibble
Thanks, updated.
I’m still wrong, but let’s slow down for a minute :)
“Historically, there have been cases where the term “nybble” was used for a set of bits fewer than 8, but not necessarily 4. In the Apple II microcomputer line, much of the disk drive control was implemented in software. Writing data to a disk was done by converting 256-byte pages into sets of 5-bit or, later, 6-bit nibbles; loading data from the disk required the reverse. Note that the term byte also had this ambiguity; at one time, byte meant a set of bits but not necessarily 8. Today, the terms “byte” and “nibble” generally refer to 8- and 4-bit collections, respectively, and are not often used for other sizes. The term “semi-nibble” is used to refer to a 2-bit collection, or half a nibble.”
8bits is still not a nibble, but there is precedent for ‘less than the standard memory chunk size on this platform” usage :)
“modern IDE storage” :-)
I like it, it’s one of those things you need one day when you don’t have one, wish you had and you know its gonna cost ya :p
Fyi, while ide data is 16 bits, the control commands only use 8. So you can do a simple 8 bit interface with no multiplexing if you are willing to throw away half the disk and have a nonstandard format.
Not that doing it right doesn’t have merit.