Re: Looking for a Micro SCI disk controller

["Bill Garber" <willy46pa@comcast.net>]

"Eric Smith" <eric-no-spam-for-me@brouhaha.com> wrote in message
qhllnmulin.fsf@ruckus.brouhaha.com">news:qhllnmulin.fsf@ruckus.brouhaha.com...
: Specifically, with the Apple Disk ][ controller:
:
: The P5 (341-0009) and P5A (341-0027) PROMs contains 13- and
16-sector
: boot code, respectively.  This determines which kind of
diskettes can be
: booted directly, but does not affect which can be accessed.  It
is
: possible to boot software from a 13-sector diskettes that knows
how to
: read and write 16-sector diskettes (but see the P6 notes
below).  For
: instance, there was a hacked version of MUFFIN, Apple's
: 13-sector-to-16-sector utility, that worked in the reverse
direction.
:
: If you have a P5A PROM and want to boot a 13-sector diskette,
you'll need
: to either boot the BASICS disk first, or boot DOS 3.3 and run
BOOT13.
:
: The P6 (341-0010) state machine PROM can not read 16-sector
diskettes
: reliably.  It should only be used with 13-sector diskettes.
The P6A
: (341-0028) can read both 13- and 16-sector diskettes reliably.
There is
: no reason to use the old P6 state machine PROM, even if you're
going to
: use a P5 13-sector boot PROM.
:
: On the other hand, installing the P5A and P6 together is asking
for
: trouble, since it would only be able to boot 16-sector disks
which it
: would be unable to read reliably.
:
: Of course, normally the PROMs were used in matching pairs.
Controllers
: that were originally shipped with the P5 and P6 were generally
upgarded
: to the P5A and P6A at the same time.

So, basically, if I have the 0027 and 0028 proms, I can read
and write both 13 and 16 sector disks, so why would I want
the older ones?    8)

: Speaking of which, has anyone got any extra P5 or P6 chips
they'd be
: willing to sell or trade?  At the very least I'd be willing to
provide
: a P5A and P6A if anyone needs an upgrade.

Let me check, I have a box full of Disk II controllers and
some of them wouldn't read 16 sector disks, I wondered why.
Could be they have the older roms.

: Failing that, a copy of the P5 and P6 bit patterns would let me
burn my
: own, assuming that I can find some blank 6309, 82S135, 82LS135,
: TBP18S22, 74S471, or 74LS471 PROMs.

Good luck finding the chips. I couldn't even find
data on them, anywhere! What do you burn those with?

: Back in 1980 I programmed a double-size PROM (512x8) with the
contents
: of both the P5 and P5A PROMs, and wired the extra address line
to a
: switch on the side of my Apple ][+.  IIRC, the PROM was a Texas
: Instruments TBP28S42, though the 82S147, 6349, 7649, 74S472, or
74LS472
: should also work.  I had to write a little program to reformat
the data
: because of the way the address lines are arranged on the larger
chip.

I want to do that with my //e, but I only have 28 pin
socket, so I either stack and solder the pins all but
the power pins, or build an adapter to somehow install
the larger 32 pin eprom.

Bill @ GarberStreet Enterprizez };-)
Web Site - http://garberstreet.netfirms.com
Email - willy4SPAM6pa@comXcast.net
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