test-drb October 2020

test-drb@ccmp.vtda.org

136 participants
117 discussions

by aek＠bitsavers.org

http://mnembler.com/computers_mini_stories.html "George Dragner always wore a belt with a metal dragon buckle. He was a colorful character known for pissing off management. His most famous act was tossing a chair through the window at a customer site. The customer refused to believe that the lack of humidity in the room was screwing up his magnetic tape media. As the tape heads depend on the moisture from the air to prevent the magnetic oxide from being torn off the media from the friction during a rewind. George broke the window to prove his point. He was right ! " There is a minimum RH specified for tape, but "tape heads depend on the moisture from the air" ??

4 years, 1 month

removing melting rubber from metal?

by kfergason＠gmail.com

Hi All, I have an EP-1 eprom programmer from BP Microsystems. The rubber feet melted. It was in my closet. I have no clue how it got that hot, or if they are just some composition for them to melt. My question is how do I clean this up? Acetone, paint thinner? I scraped off the feet, so there is just a few 'streams' of melted rubber down the sides, and a bit that somehow got inside (also on the side, not on the electronics). Just looking for some ideas before I start applying chemicals... Thanks, Kelly

4 years, 1 month

MOP boot files

by abs＠absd.org

I've been helping dreamlayers with his cleanup of the NetBSD/Linux mopd, ( https://github.com/dreamlayers/netbsd-mopd ) and we were looking at how it handled different a.out MOP files, specifically where the files may be little endian For non MID zero files its easy enough, but little endian MID 0 files are potentially more complicated. https://github.com/abs0/netbsd-mopd/commit/6ab8555817f3dff23c506464d302d1a4… It can netboot Ultrix and the vast panoply of NetBSD MOP boot files in the various a.out and ELF incarnations http://mop.absd.org/netbsd/ (those that are not broken that is :/ ) I was wondering if anyone had links to hand for any other good sources of MOP files? Thanks David

4 years, 1 month

DG Nova panel font?

by rsmilward＠frontier.com

Speaking of DEC fonts, does anyone know what was used on the Data General Nova machines? Thanks! **Richard IBM 1620 > IBM 1130 > S/360 Model 40 > DG Nova > ...

4 years, 1 month

Font for DEC indicator panels

by jnc＠mercury.lcs.mit.edu

> From: Toby Thain > To get closer I'd need better images of the panels. Hi, I borrowed a DEC inlay from someone (a KA10 CPU bay) and scanned a chunk of it (as much as I could fit into my A4 scanner :-) at 200 dpi: http://ana-3.lcs.mit.edu/~jnc/tech/jpg/KACPUPanel.jpg I have a TC08 inlay, but it's currently being used in my QSIC display (until we can get the RKV11-F/RPV11-D inlay done :-), and I didn't want to yank it out. As far as I can tell, it's the same font on the two of them. > the closest I know of off the top of my head is Akzidenz Grotesk. The Akzidenz Grotesk Medium is indeed very, very close (other than the zero). Do you happen to know if that font available for use in non-commercial settings? Thanks! Noel

4 years, 1 month

Next project: 11/24. Does it need memory?--Working-ish!

by jnc＠mercury.lcs.mit.edu

> From: Chris Zach > The last board is a new style 11/24 and it doesn't do anything but it > does have three switch packs. So I just need to find the manual for it Appendix D in the 003 rev of the /24 TM has the details of the -YA.. > In the meantime the UNIBUS problem also appears to be fixed: The > problem was that sure enough: One of the memory slot SPC's (4) did not > have the DMA jumper. Checking grant line continuity is part of system setup for me; the fact than on many backplanes, the DMA grant jumpering is wirewrap on the back of the backplane is a PITA, but back when it wasn't that big a deal. (Heck, configuration jumpering on boards was all soldered wires BITD!) The need for grant continuity is actually a characteristic of the _CPU_, not the bus. I was astonished the first time I played with an /04 (or naybe it was a /34, I forget), because on them, I'm pretty sure (I can't find it in the documentation, but I'm pretty sure I remember it) that on power-on, the CPU checks for grant continuity, and won't work without it. (They all require the M9302 teminator or equivalent, which has active circuitry to turn around an unclaimed grant onto the BSACK line.) When the CPU powers up, it sends grants down the grant lines and expects to see them back on SACK (from the M9302), and it won't operate if this doesn't happen. That floored me when I ran across it, because on the older UNIBUS CPUs I'd worked with BITD (/40's, etc) it was the done thing to be able to leave a gap in the grant _downtream_ of the last card that could do interrupts; no possible operational problem. I'm not sure why DEC added that 'feature'; probably somebody thought it would make systems more robust, but I bet all it did was generate a bunch of Field Circus calls. (Kind of like the LSI-11 'feature' where ODT won't start unless there's working memory at 0 - another wonderful little Easter Egg.) Ironically, although the QBUS uses _exactly_ the same kind of bus grant lines, no QBUS processor seems to check their continuity in this way; I habitually run my QBUS machines without all the slots filled, and F11 and J11 processors all run fine with open grant lines (after the last card that uses interrupts). I guess DEC found out the hard way that that check wasn't useful! But this, as I said, is a characteristic of the CPU, not the bus. > Anyone even know why Q-Bus doesn't need termination QBUS documentation has long ediscussions of maximum cable lengths between backplane sections, but little about cases where termination on both ends is not needed. One exception is in the " pdp11 bus hanbook", pg. 128: If nore than 20 AC loads are included [on a single bacplane], the other end of the bus must be terminated with 120 ohms. The clear implication is that with <20 AC loads, termination at the second end is not needed. No explanation is given as to why, but I had the same thoughts as Patrick Finnegan - that it's down to the very short bus lengths. (With a short bus, the reflection from the un-terminated end will be very close in time - the line length for the lines on a single backplane is spec'd at a max od about 14"; so about 1 nsec. That's on the order of magnitude of the bus signal rise times.) If you think about it, every time you plug in a card, you've added a short branch to the bus on every bus line (since they aren't normally terminated at the transmitter/reveiver chips). But very short branches, so their reflections are even closer in time. Noel

4 years, 1 month

Next project: 11/24. Does it need memory?--Memory sad!

by technoid6502＠gmail.com

Those sound like ram chip 4116, quite common once, and still available. I have a couple dozen tested ones handy if you want them. (From Atari 800 16k ram modules). 250ns to 350ns, depending. best, Jeff On Tue, 2020-10-27 at 12:00 -0500, cctalk-request at classiccmp.org wrote: > Re: Next project: 11/24. Does it need memory?--Memory sad!

4 years, 1 month

R65F11

by decguy＠songdog.eskimo.com

Anyone remember the R65F11? It's a Forth microcontroller: 6502 processor with a Forth kernel in ROM, from the mid '80s. I was going through some old stuff in storage (looking for something else) and found an R65F11 with the development ROM and some documentation for building a development board. Looks like a fun little project... I have plenty of projects. If anyone is interested, it's free for actual cost of shipping (could probably go in a U.S. Priority Mail envelope or small box, not sure about overseas options). The backstory: in 1984 I was working for a startup company, and we were looking at various microprocessors for use in a new product. Being a fairly skilled journeyman Forth programmer, I was advocating for the R65F11. I managed to talk the Rockwell sales rep into giving us the development ROM (usually not easily available). We ended up going with a 68000 for the project, and I ended up with the R65F11.

4 years, 1 month

Next project: 11/24. Does it need memory?

by jnc＠mercury.lcs.mit.edu

> From: Chris Zach > Next up is the 11/24, this is one of the 5.25 inch rack mounts with a > CPU, KT24, and no memory. > First question: Will ODT respond at all with no memory on the Unibus? My _guess_ is probably, since on other KDF11 CPU's, ODT works with no memory, but I haven't confirmed that. My PDP-11/24 chassis (a 5-1/4" BA11-L, like yours) I took apart to get the backplane out, so I could work out how the busses work (see below), and I'd need to put it back together before I could try my -12/24.to confirm it. If you could take some pictures of the insides of your BA11-L, that would be both a help to the re-assemblhy, and ancentive to do so. > Can a 128kw memory board from an 11/34 work in an 11/24? Yes and no. See: https://gunkies.org/wiki/PDP-11/24 for more. Note "The top 256 Kbytes of the CPU's address space were devoted to the UNIBUS". So an MS11-L or similar UNIBUS memory can probably be read/written by the CPU, but it won't appear at 0 in the CPU's address space. > Or do I need one of the 11/44 boards to make it go? Whether a KDF11-U will work with no memory at physical 0 is unknown: it would need at least a special bootstrap (since most assume working memory at 0) and a special OS load (ditto). Also, I seem to recall that on the -11/45, with mapping enabled, interrupt vectors are in Kernel D space, so once running, that machine could operate with no working memory at physical 0, but I don't know if KDF11 CPU's use mapped Kernel space for vectors. If you're interested, I can run an test on a KDF11-A and see. Noel

4 years, 1 month

IBM 360/30 panel, animated, restored

by jwsmail＠jwsss.com

This popped up on the radar tonight (on mine anyway). IBM System 360 30 Console animated mainframe CPU Console 360/30 https://www.ebay.com/itm/324348449949 A bit pricey, but pretty. Luckily I landed one of the boards to run Larry W's emulation of the 2030 , which will be satisfying for me.? (And thanks for releasing that work). Thanks Jim

4 years, 1 month

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test-drb October 2020