Re: supercard + hardware details

Hi,

Groepaz schrieb:
> inspired by a recent thread on lemon i have added supercard+ emulation to VICE 
> and in the process tried to find some documentation on that hardware (so i 
> dont have to guess) - with very little success.

some time around 2006 I attended several discussion thread in c.s.c
about CLD's RAMBOard series and also MegaSoft's The Shadow and Utilities
Unlimited's / Jim Drew's Supercard series also. Some basic information
about address decoding and such was exchanged. Maybe it's worth to
search G's archives.

> i figured out that it is 
> basically just a 2k ROM sitting at $1000, plus a 8k RAM at $6000 - and 
> implementing just that seems to make it work in VICE (grab the latest svn 
> version if you want to try).

From a reverse engineered high resolution TIF image file that someone
shared to me and a derived not validated Eagle schematic file I confirm
that 8K SRAM are by default configured (74LS138) to address location
0x6000...0x7FFF with a "PAD1" option for address location  0x4000...0x5FFF.

Decoder output Y0 (0x0000...0x1FFF) is put to a second 72LS138 along
with A11 and A12, so that Y2 selects address space 0x1000...0x17FF to
enable the 2764 EPROM. Therefore only 2K of the 8K ROM are usable.

Note: Part of Jim's greetings to the world are hidden due to the 2K
limitation.

Note 2: The 2K limitation was probably needed to also support the 1571
default memory map without too much hassle on "emulating" open address
space to the 1571n mainboard while the SC+ ROM is enabled.


> however, i understood that there is/was an 
> additional index hole sensor which is atleast supported by one of the 
> copyprograms for this card - i would be interested in any information on that 
> one, especially where it was connected to :) (that would save me from 
> disassembling the IHS-nibbler in order to find out how it works)

Nate told this already, this sensor consisted of a file with
instructions on one of SC's utility disks

> it seems that some people have already collected a bunch of related stuff (you 
> know who you are) back in 2006 - but unfortunately only the disk images and 
> scanned original docs are "around" on the net, no schematics or any other 
> details like that :/ (just for curiosity, i'd also like to know what exactly 
> the two "clips" coming from the card were used to, somehow i feel like they 
> werent really necessary *shrug*)

Hmmmmm, .... in my schematic I added PAD1....PAD7. PAD1 is the RAM
address location option described above. That one may correlate to PAD5,
6 and 7 from the open address space emulation circuit (74LS157).
Probably these pads along with the clips are needed to support specific
drives ????

Ah yes, there it is. From the 1571 installation instructions:

  "
  [...]
   9 - Now, solder a 12" piece of wire from the SUPER-CARD+ board at
       the
       location marked '71'.

  10 - Remove IC-U20.  It will be a 6526 or 8521.  Locate PIN 23 and
       SLOWLY
       slowly bend this pin out to the side enough so that when you re-
       install the IC, the leg does NOT go into the socket.

  11 - Solder the other end of the wire from the SUPER-CARD+ board to
       PIN 23
       of IC U20.
  [...]
  "

So then PAD1 in fact is needed to select the 1571's CIA ony for
addresses 0x4000...0x5FFF.

Don't know, what all the other PAD options were intended for. In some of
Jim Drew's interviews about The Shadow he told about one of his early
hardware hacks. Either that hack should be supported by The Shadow also
which was developed by someone else or he his hardware was inspired by a
similar technique from The Shadow. However, with a flip of a switch Jim
was able to instantly swap the disk drive's internal 2K of RAM with
another set of 2K RAM (perhaps part of an 8K chip) and then reset the
drive. That way the drive did not overwrite anything that was previously
stored to its internal RAM. Jim said that this shadow RAM was an
invaluable help on analysing custom and protection loaders.

Although _I_ don't see it, maybe the SC+ can be configured to support
such a RAM shadow switch.

> so if anyone can provide that info, please feel free to throw it into my 
> direction :)


Womo

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