Conference 7.286::atarist

You would need a special program to format (ie: TOS won't even format 10
sectors let alone 18). TOS should read and write the disks with no problems
after they are formated.

	Ray

  RE: .0

    The WD controller chip is also not rated for 16mhz.  There have been
some people who have made the modification you mention on USENET and had
it work, and others it failed for.  Atari had a faster version of the chip
manufactured I think in Israel, and it should be available <Real Soon Now>.
This is of course Ataris definition of RSN which the rest of the world 
does not follow.  (DEF: RSN (see Atari Blitter for 520/1040,ROM drive,
Atari TT,Stacy,FSM GDOS...))

bill powers

    I have done this - and it works just fine!

    Yes, you double the clock for the WD1772 floppy controller chip. But
    there is more:

    Not all types of WD1772 are capable of handling the 16MHz. From various
    sources I know that you must have a chip with some number ending with
    '002', not the '001'-type.

    Secondly, the steprate also is controlled by the 16MHz and thus too
    fast.

    A colleage of mine developed a little cirquit that basicly does the
    following (that's the thinggy I have built into my MegaST):

    Some little logic twiddling makes it switch from 16MHz back to 8MHz
    whenever a) a step pulse is issued (controlled by a 3ms monoflop, b)
    whenever there is NO HD signal from the drive. The second point (b) is
    further dependant on the drive select signals. This all together gives
    a HDcontroller that allows for independant use of floppy A: and B: in
    any configuration of normal and HD drives. It also allows replacement
    of either drive with low and/or high density drive without any rewiring
    or reconfiguration.

    The whole thing has s size of 4cm by 5cm (1.5" by 2") and contains
    only 3 standard TTL chips (no GAL etc).

    I will contact my friend and ask wether he allows for posting more
    details, please be patient.

    
    ---markus---

Thanks everyone for your replies,

Markus, I certainly would be interested in the fix, I await it eagerly, Thanks.

Basically to sum up peoples responses:

	The fix of using 16Mhz gated from the HD select signal of the 
	Drive needs to be further modified to switch back to 8Mhz when
	a step pulse is issued on either type of disk. Also 8Mhz needs 
	to be selected when a non HD disk is used.

	Once this is installed, formatting will have to be done via a 
	special program (or a PC Perhaps ?)

	When a HD formatted disk is inserted and recognised (by it's extra
	little hole) the TOS will be able to read and write quite happily
 
	Obviously this all needs the use of a HD disk drive.

Does owning a brand new STE (1 month old) improve my chances of getting this to 
work with my WD 1772 controller ?

Brynn (who's next job is a Hard Disk)

    more to my reply (.3)


    I asked my friend about his cirquit and here is what came out:

    quote:
      The floppy controller WD1772 is normally clocked with 8MHz for DD
      drives. Doubling the frequency will allow HD drives to be used in HD
      mode. You must have a newer model of the WD1772 chip. The older one
      with a number 00-02 will not operate at 16MHz. If your chip is of type
      02-02 it will work fine. Sometimes it might get a little warm, just add a
      small cooling device, but this should not be neccessary.

      The clock to the WD1772 (pin 18) must be replaced by a new signal, that
      can be switched between 8MHz and 16MHz.

      The cirquit provides this clock and switches from 8Mhz to 16MHz clock
      when:
	- one of the drives is selected (drive select active)
	- and the selected drive is a HD drive and has a HD disk inserted

      During the step pulse the clock is also always 8MHz. Many of the
      commercial HD kits manage step pulse length by software. They program
      the WD1772 to 6ms step pulse length. With this cirquit you have a
      hardware solution and do not need any software for it to work.

      All the signals are buffered.

    endquote.


    
    My friend has has done a very nice drawing of the cirquit but has not a
    full description of the workings. You can ask me for photocopies of his
    drawing and a short description of how to connect it to the ST. If you
    build the cirquit and find it useful please let my friend know by
    sending him a postcard (is this the harware equivalent of
    'postcardware' ?).

    The cirquit comprises of 3 standard TTL chips, 2 capacitors, and 4
    resistors. Optionally you can add a 16MHz oscillator or get the 16MHz
    from the video shifter. --> very low cost!!

    Please contact me via mail (BERN01::RUGGIERO) if you are interested.


    And for the lawyers
    
    disclaimer:

    The cirquit works fine in several 1040ST and MegaST. It works in my
    own MegaST without any problems. It may however not work in your
    computer/with your drives, it may even cause damage to your system
    and to your data. Neither me or my friend are responsible in any way.
    Build and use it at your own risk.

	I sent a mail to Markus, and as promised he sent me back a paper copy
	of the little circuit his friend has drafted.
	I went to my usual Electronic Components shop and unforfunately, none
	of the 74HCTxxx ICs were available.
	Does anyone know if another series will do, especially the 74LFxxx 
	series ? I have seen "principle schematics" using 74LFxxx circuits
	for the same purpose.