Nice work, indeed! The clearance issue is part of why I made the repair module boards.
Thanks, Jonathan On Wed, Dec 5, 2018 at 9:54 AM Maciej W. Rozycki via cctalk < [email protected]> wrote: > On Sun, 2 Dec 2018, Jeffrey S. Worley via cctalk wrote: > > > The re-work of that Dallas nvram chip is just beautiful. It makes me > > ashamed of myself. (I just chopped into the epoxy with a pocket knife, > > soldered two leads, and velcroed the new batteries somewhere inside the > > machine I installed it in.) > > There is very little clearance in DECstation 5000 systems, like .1", as > per the TURBOchannel specification, between the top of the Dallas chip and > the bottom of any TURBOchannel option placed right above it (some have > components underneath, including large ICs), and I think the risk of > breaking such a non-standard wiring while shuffling option cards is not to > be ignored either. Also the design of the system box makes it very > difficult to choose a suitable location for a distant battery holder that > would not obstruct anything. > > So I decided to do that properly at the cost of it taking perhaps a > little longer to rework a single chip. > > NB a CR1220 cell is supposed to last for ~8 years in this application if > running on battery power all the time, which I think is good enough. A > CR2032 cell would last ~50 years, which I think is an overkill, given that > the seal is expected to fail much earlier, like after 10 years. > > An encapsulated power module could instead be used such as the Renata > 175-0, where space permits, which would indeed last some 50 years, being > airtight, but I haven't seen any reports of its use in this application (I > have a couple of those on DEC NVRAM boards and last time I checked they > still had the power to hold 1MiB SRAM memory contents after 25+ years). > > > I salute you sir. > > :) So far I only made 2 of these, but more are in the pipeline (waiting > for a free weekend). > > Maciej >
