Further PDP-11/05 debugging -- core memory faults

Brent, On Sat, Sep 6, 2014 at 2:53 AM, Brent Hilpert <hilpert at cs.ubc.ca> wrote: I read your linked article - very enjoyable, informative and clearly-written piece. You really managed to pack a lot of interesting detail into it, and the diagrams are quite good. The details on actual physical topologies (and functional electrical layouts, with actual write / sense amplifier designs), the weaving together of bit-planes into words and finally modules are something I haven't come across on-line before. A thought.. if you still have access to the hardware cited in the article, it would be neat if you could add another column or two to the table fig.11 - one for volume, one for mass.. just for amusement purposes. ;-) One lingering question though.. why on earth were the big iron manufacturers still building massive core memories as recently as the late 1970s? As early as the mid-1980s, 64K of (faster!) SRAM could be bought for around a hundred dollars. Clearly these core modules are orders of magnitude more costly.. so why were they still being produced? It can't only be a matter of their non-volatility?