Found these inside a non-working 71B

[Paul Berger (Canada)]

(03-15-2018 05:09 PM)MikeSD Wrote:  If I said that, I must have been tired. I think the only place I used 10 is that the U9-9 is routed to the Math ROM-8 and also to pin 10 on U9, for some reason.

I noticed there is a Forth Assembler part number for "with and without" a debugger. My part number is for the with debugger. Wonder how I verify that? Is the debugger a hardware item, or another ROM, or part of the Assembler?

Thinking out of the box
* I have a ton of 4K RAM boards, from salvaged 71Bs.
* And I have 4 unused front ports.
* And, I bet I could wire in some special connectors deep in those ports, to allow a kludged 8K RAM, made of 4K,
* to be inserted in and plugged into a special connector THAT wouldn't interfere with a standard plugin, if the RAM was removed.

Think that's possible? Can 8K RAMS be made, or do only 4K, 32K and 64K work as a group.

OR, I could put as many together as I could, that might fit in the Card Reader Port. Would like to find a good use for the 4K RAMs.

The circuit board assembly used for the internal 4K modules is identical to the one used on the 4K front plug in module. This module is a hybrid composed of 4 1KB chips, but appears as a 4K module because only one chip reports "Last chip in module" so the OS treats them as a single unit of memory. In order to be able to get the OS to treat two as an 8K module would be to prevent the last chip of module one from reporting last chip then it would combine all the chips in the module with the chips in the next module on the daisy chain and the OS would then treat them as a single unit equal to the sum of all the chips in the combined modules. I don't know if this is possible with the 4K modules, but it certainly is not documented.

It would be possible to connect the modules to a front port or to stack some up in the card reader port. I have a specially constructed front port module that brings the bus lines out to a connector on the front that I initially built to monitor the bus, but recently have been using to test memory modules and it now has a 128K module attached to it that I am running looped diagnostics on. The card reader port is easier to connect to. The small size of the 4K modules makes them less attractive for front port or card reader port modules but they will work.