On Fri, May 2, 2025 at 11:53 AM Jonathan Chapman via cctalk <cctalk(a)classiccmp.org> wrote: I have a Grant Technologies 306A/307 I found in a MicroPDP-11/53 I bought a few years back. Yes... NiCd damage under the battery, fortunately very minor. -ethan

Thanks for the info! I'm going to have to widen my search for sure. One of those 306A or 307 cards sounds like they should work. - Peter On Sat, May 3, 2025 at 12:08 PM Christopher Zach via cctalk < cctalk(a)classiccmp.org&gt; wrote:

My note in the DEC VCF forum might give you some more background. https://forum.vcfed.org/index.php?threads/real-time-clock-card-gtsc306a-add… https://bitsavers.trailing-edge.com/pdf/gtsc/979-0021-306_GTSC306_Sep88.pdf The DEC KWV-11 is designed to support analog and digital acquisition boards. See EK-ADV11-OP-002 ADV11-A, KWV11-A, AAV11-A, DRV11 User's Manual.pdf. On Sat, May 3, 2025 at 9:18 PM Ethan Dicks via cctalk &lt;cctalk(a)classiccmp.org&gt; wrote: -- jsw(a)ieee.org

Neat! Is the rsx code or source code for the rtc anywhere? It's less necessary now that we have ntp from the tcp stack (thank you bqt) but it would still be cool On May 4, 2025 2:08:35 AM EDT, Jerry Weiss via cctalk &lt;cctalk(a)classiccmp.org&gt; wrote:

Source code for the rtc -- the KW11-L and KW11-P diagnostics are available on BitSavers et al via goo. MAINDEC-11-DDKWA for the KW11-L line frequency clock and MAINDEC-11-DDKWB for the KW11-P real time clock (ie 50/60/10k and 100k Hz). I appreciate this is agricultural, but these are probably the best specifications of the KW11's available. There are also the KW11-W watchdog timers, the Qbus derivatives, counter / timers boards to support data acquisition, and of course the time of day clocks. Usage of the CSRs and vectors seems quite a fankle, but that is an XFU. Specimen CSR/VEC/BR may be - line frequency / programmable clock 777546 / 100 / BR6 - watchdog timer 777544 / 104 / BR7 - ToD RTC float / float / BR4 HtH; Martin -----Original Message----- From: Peter Ekstrom via cctalk [mailto:cctalk@classiccmp.org] Sent: 04 May 2025 15:35 To: General Discussion: On-Topic and Off-Topic Posts &lt;cctalk(a)classiccmp.org&gt; Cc: Peter Ekstrom &lt;epekstrom(a)gmail.com&gt; Subject: [cctalk] Re: PDP-11 hardware clock It is still a 'good to have' for those running real PDP-11 machines without I/D support, like the 11/23 and 11.23+. The TCP/IP stack Johnny has written works great on the machines (emulated or real) that do support I/D space. I would really like to have Johnny's TCP/IP stack on my 11/23+ but I understand it is a big undertaking to modify the stack to work on non-I/D space systems. DECnet works though but lacks NTP-like utilities. -Peter On Sun, May 4, 2025 at 10:23 AM Christopher Zach via cctalk < cctalk(a)classiccmp.org&gt; wrote:

Oh! Thank you for that! I didn't know about that one. -Peter On Sun, May 4, 2025 at 1:18 PM Glen Slick via cctalk &lt;cctalk(a)classiccmp.org&gt; wrote:

On 5/4/2025 1:10 PM, Glen Slick via cctalk wrote: If you have a free serial port there is always an old GPS receiver like A Delorme Tripmate. They show up on eBay all the time. And, now I have an even more interesting idea. I have built a couple of different clocks based on things like the Arduino and The Blue Pill. I expect it would not take much to add serial port output on one of these and use it to feed time to an old system. bill

GPS modules can now be had from various outlets for $20 or so, perhaps less depending on specs. I got one from Adafruit recently that will track 15 or more satellites, and deliver time to a modest number of nanoseconds. Some have embedded antennas that work quite well even indoors (though I would assume not if you have solid metal layers in the ceiling). The common standard is NMEA, which is well enough described in product data sheets (the ones from u-blox are particularly good, and they also make good GPS modules at prices somewhat higher than Chinese competitors) even though the standard itself is annoyingly secret. It's a simple serial protocol on a 9600 baud link, so a PDP-11 can easily process it. If you want time to the nearest second, just parsing the incoming NMEA message is sufficient. If you want to do better, hook up the GPS module's PPS (pulse per second) line to a convenient logic level input, perhaps a modem control signal of a serial port or an input line of a GPIO digital controller. That will get you second signals to far better than the interrupt latency of a PDP-11. paul

On Sat, May 3, 2025 at 12:08 PM Christopher Zach via cctalk &lt;cctalk(a)classiccmp.org&gt; wrote: OK. I did some digging around for 3 year old conversations and links. The Grant Technology 306A is the fully-stuffed KWV11 + RTC board. If it's 1/4 stuffed with just the RTC portion, it's a 307. Manual at: http://bitsavers.informatik.uni-stuttgart.de/pdf/gtsc/979-0021-306_GTSC306_… RT-11 routines at: https://archive.decromancer.ca/pdp-11.classiccmp.org/RT-11/freeware/decus11… One 306A sold last year on fleabay for $27 plus shipping. If I had seen it, I probably would have bought it. I don't think there are any photos easily findable online. The manual on bitsavers has some great technical details but sadly no schematic. Enjoy, -ethan