On Mon, 31 Jul 2017, Rob Jarratt wrote: > > It is. Check the "DECstation/DECsystem 5000 Model 200 Series Maintenance > > Guide" (EK-PM38C-MG-002), available online. > > > > I have that manual. Having checked again I realise I should have searched > for "NVR" and not "NVRAM", then I would have found it!!
Or "jumper" would do too, ;) avoiding DEC documentation peculiarities (they indeed call the Dallas chip "NVR", reserving "NVRAM" for the MS02-NV Prestoserve SRAM memory board). > > Technically it's wired to one of the 16 IOASIC external interrupt inputs, > which is > > otherwise unused. Functionally it tells software whether the mainboard is > used > > in a 5000 or a 5900 system configuration. I can dig out the exact details > if > > you're interested. > > > That would be interesting, if there is documentation that isn't generally > available it would be good to see it. Not everything has been properly documented, I've gathered information from various sources, including reverse engineering. The bigmax IOASIC IRQ bit is I recall only mentioned in an Ultrix error log processing utility, though the jumper itself is I believe mentioned in one of the 5900 manuals, available online. Over the years I've gathered available information in Linux kernel headers; for the KN03 mainboard specifically: <https://git.linux-mips.org/cgit/ralf/linux.git/tree/arch/mips/include/asm/dec/kn03.h> Interpreted along with: <https://git.linux-mips.org/cgit/ralf/linux.git/tree/arch/mips/include/asm/dec/ioasic_addrs.h> and knowing that in the console you need to use the MIPS KSEG1 uncached address space you get: KSEG1 | (KN03_SLOT_BASE + IOASIC_IOCTL + IO_REG_SIR) which expands to: 0xa0000000 | (0x1f800000 + 1 * 0x00040000 + 0x110) => 0xbf840110 so to get at the interesting bits: >>e -wx 0xbf840110 bf840110: 0x00008802 >> i.e. the bigmax bit is set as for the 5000/240 (jumper present), the NVR clear bit is clear (jumper absent), and the NRMOD bit is clear (jumper absent). There is also a TURBOchannel slot #0 option interrupt pending here for some reason and the halt button is released. > > BTW I saw your 5000/240 web page and I'm glad that you have rescued all > > that fine hardware. Also I think you don't have to worry about the H7878 > PSU -- > > apparently none of the caps used in that model suffers from the dreaded > > quaternary ammonium salt issue. > > > Thanks. I will create a page describing the machine in the coming days, for > now it will just be the blog posting. I do think there is a problem with the > PSU though because it will be just sitting there in the console and power > off, you can't turn it back on until you pull out the power cord. I am going > to check the caps more closely. Always worth doing of course, although from its arrangement the H7878 would be a pain do disassemble to reach some of its caps. Also check for the PSU overheating condition, reported at bit #4 in the IOASIC interrupt status as examined above (with good status indicated with the bit clear). It may cause the PSU to eventually shut itself down. Maciej
