Found these inside a non-working 71B

[Dave Frederickson]

Okay,

With the CMT-71-P01, when the switch is in the 32k position, I measure 6.49V on Pin 11, with the blue wire. When in the 64k position I measure zero.

(03-16-2018 02:04 AM)Sylvain Cote Wrote:  Remember that the CMT-71-P01 is able to create a 64KB module (free ported RAM) only if the FORTH/Assembler module is present (page 3 of the Instruction Manual).
Sylvain

The manual states,

To use the programmer in the 64K mode, a FORTH/ASSM ROM needs to
be inserted into another HP-71 port.

There's no problem creating a 64k port without the F/A ROM, see below.

Code:


/* This is the 2CDCC machine I have hooked up to the P01 in Port(4).
>SHOWPORT
0.05  16384  2
0      4096  0
0.01   4096  0
0.02   4096  0
0.03   4096  0
4     65536  0 \* The switch is in the 64k position
5     32768  0 \* CMT 128k RAM
5.01  32768  0
5.02  32768  0
5.03  32768  0
>
>FREEPORT(4)
>
>MEM(4)
 65531 \* Port created
>
>VER$
HP71:2CDCC HPIL:1B \* No F/A
>
\* Switching to 1BBBB with the 64k bug
>VER$
HP71:1BBBB HPIL:1B
>
>
>SHOWPORT
0.05  16384  2
4     65536  1 \* IRAM is still there because the P01 is still powered
>
>CLAIMPORT(4)
>SHOWPORT
0.05  16384  2 \* P01 RAM is now in MAIN
>
>FREEPORT(4)
>MEM(4)
 65531 \* FREEPORT okay
>

An additional description of the bug can be found in the 1985 Atlanta Conference Proceedings, pp103-104, in an article by Jim De Arras from HHP, describing the discovery of the bug when he first delivered the 64k modules to HP.

The bug is easy to duplicate with Emu71. As described in the article, it occurs when EDIT is invoked on a 64k IRAM configured at E0000.

Dave