Looking for info on National Semiconductor RAM board (VAX 11/730)

[tony duell]

[Argh! Following up my own post :-(]

> I am looking for any information on a National Semiconductor RAM board that I think goes in
> a VAX 11/730. My 11/730 (which admittedly I have not run) has 2 DEC MS730 boards and 2 of these
> NatSemi boards, I found another one while unpacking stuff today.

[...]

> The only identification I can find on it is in the etch :
> 
> PWB 551109464-002 B
> PWA 980109464

[...]

> There seems to be one RAM too many!. The main RAM array is 4 rows each of 32 4164-like DRAMs.

> Rest of the board is TTL drivers, etc. There are 2 LEDs, one green, one yellow. And a momentary pushbutton
> switch. I have no idea of the functions of those.

That switch may well be latching (alternate action). I wasnt't pressing it hard enough. It seems to be 
wired directly to the yellow LED (amongst other things).

I have found a mention of this board in an 11/750 FAQ (not surprising, I think the same 1M boards can
be used in the 11/750 and 11/730). It appears that in normal operation both LEDs are on. Pressing the
button turns off the yellow LED and completely disables the board. Quite why you'd want to do this I do
not know...

Oh, and it mentions a 'spare RAM chip in a socket on the board'. All RAM on my board is, indeed, socketed.
If this is just an unused chip to substitute if one fails then I think I've seen it all...

-tony