29 Sep
2014
29 Sep
'14
11:21 a.m.
On Mon, Sep 29, 2014 at 2:25 AM, Brent Hilpert <hilpert at cs.ubc.ca> wrote:
On 2014-Sep-28, at 11:10 PM, Josh Dersch wrote:
pursuit of
my crazy plan and I was initially puzzled -- it didn't actually
look like there's hardware on the board (or the associated control/driver
logic) to actually address 18 bits. I saw the sense/inhibit lines for bit
P0 and P1 outlined, but there are no associated diodes on the X/Y switches.
Thanks, that makes sense and I can see from the way things are set up that
you're probably right that this isn't going to help. Ah, all those cores
going to waste :).
On 9/27/2014 9:59 PM, Josh Dersch wrote:
> On 9/27/2014 2:11 PM, Tony Duell wrote:
>
>
>>
>> Incidneatlly, no matter what it says on the cover over the core mat,
you
>> can take it off quite easily without
damage. Just don't drop it on the
>> corse.
>>
>> If it is the core address wire in the mat, you may have big problems.
>> Some of these mats had the cores cast onto the array of wires, no
>> pre-made cores that were threaded with the wires. In which case,
>> replacing the wire might be impossible.
>>
>> My first throught was 'have a go anyway. If you wreck the board, well,
it
>> doesn't work now'. And then I
thoguth that no, you should treat it with
>> care. Even if you don't have the skill to fix it now, you might do so i
>> nthe future. Or somebody else might have a go. In any case, you don't
>> want ot make thigns worse.
>
> I do have a semi-crazy idea: The H214 I have is 8Kx18 bits (i.e.
parity). If
I were to disable parity on the control boards and reroute one
of the parity-related lines for this damaged section, maybe I could get a
complete 8Kx16?
I'll have to do a bit more research...
- Josh
OK -- I spent a bit of time looking at the schematics for the H215 in
After reading through a few different sets of documentation, it turns
out that
these lines are driven by an optional parity controller, the M7259
(which, when combined with an H215, G109 and G231 makes an MM11-LP). The
M7259 apparently contains the diodes "missing" from the H215 to drive the
parity lines. Of course I don't have this board in my 11/05, which makes
me wonder why it has an 18-bit core plane to begin with...
At any rate -- I can't find a schematic for the M7259, which would help
narrow
down which edge connector pins on the H215 are used for the X/Y
selectors for the additional parity bits. I could do this by process of
elimination, but just in case someone happens to have this scanned, I
figured I'd ask?
Unless I've missed something in the way this board is organized, I
wouldn't expect to see additional X/Y addressing diodes/selectors for the
parity bits. The parity bits would typically just be two extra bit-arrays
woven into the existing X/Y address wires.
If you envision the cores as being in a 3-D coordinate system, where X/Y
constitute the address space and Z is the bits in a word, the board is
X*Y*Z = 128*64*18.
The two parity bits added two XY planes (planes perpendicular to the Z
axis), while the bad X address line takes out one of the 128 YZ planes
(planes perpendicular to the X axis). While you have 2*64*128 'extra'
cores, and only 18*64 inaccessible cores, the extra (parity) cores are not
configured/wired in a useful way for the fault.
In principle you could hack the board to swap the bad address line with
the 'last' address line, so you were just missing 64 words at the end of
the 8K but the board traces probably aren't very amenable to such rework.
Something that might be a simple hack would be to swap two entire columns
in the X-coordinate sub-matrix, to wit: swap FD1/XS05 with FK1/XS15.
It should just be swapping two traces near the connector which goes to the
addressing board.
That should move the 64-word 'hole' from 012000 up to 036000, so the board
would provide a contiguous 15KBytes/7.5KW from 0, rather than just
5KBytes/2.5KW.
Right, I'd considered that as a last-ditch sort of thing, if the wire
cannot be repaired.
As others have suggested, I'd at least try to spot the location of the
(presumed) break in the bad address wire to assess it for potential repair
first.
I'll give it another go -- as I said in an earlier mail, the wires around
the edges of the core mat are difficult to discern because of the rather
large accumulation of dust in some places. The stuff it's stuck to is so
delicate I don't want to attempt to touch it unless I have to. Also, maybe
I missed it, but is there any way to map the numbered matrix wires on the
H214 schematic to a position on the edge of the mat? For some of the wires
it's obvious what PCB trace it connects to, for others not so much. Pin 7
of E22 is one such trace, it appears to go under the mat and from there
it's difficult to trace :).
Thanks for all the help,
Josh