test-drb June 2016

test-drb@ccmp.vtda.org

196 participants
290 discussions

by jnc＠mercury.lcs.mit.edu

> From: Chuck Guzis > It's not the refresh rate that will kill things, but the horizontal > frequency. The high voltage in most CRT monitors (and TVs) is developed > from the scanning signal via a high-voltage "flyboack" transformer > ... > Ultimately, if taken too far, the voltage in the FBT secondary exceeds > the ratings of the winding insulation; an arc develops between windings > and the FBT self-destructs So, with Chuck's explanation (above) in hand, eventually my brain turned on, and I was able to work out what the deal is, and whether my monitor is safe; it also explains the somewhat contradictory CRT monitor manual: HP M50 manual says "Setting the screen resolution/refresh rate combination higher than 1024x768 at 60 Hz can damage the display." Even though the same document lists the vertical frequency range as "50-100 Hz"! They mention both the resolution and "refresh rate" since those two together control the horizontal flyback frequency, which Chuck pointed out as the key. (Well, the line count - 768 - is involved there, not the line length in pixels - although the latter will influence the maximum video bandwith or "dot rate" that needs to be supported - 65 MHz for this particular monitor.) The horizontal retrace frequency is simply the vertical retrace frequency, times the number of scan lines per vertical retrace plus a small slop factor for the actual retrace duration. So my monitor was running 1024x768 - but interlaced, so only 364 lines per screen scan (alternating odd and even lines in successive scans). I was seeing a refresh frequency of 44 Hz - but for full scan of all lines; the actual vertical retrace is being produced at 87 Hz. So the horizontal retrace frequency is about 87 * 364 = ~32 KHz - well within what the monitor can handle (30-49 Khz for the horizontal retrace, per the spec). So the monitor is safe! Probably by the time this monitor came out, the interlaced XGA format had fallen into disuse, and so they didn't need to clarify that "resolution/refresh rate combination higher than 1024x768 at 60 Hz can damage the display" refers to 'progressive' displays, not interlaced. And of course, as previously pointed out, the interlace explains why no LCD displays will work. So I'll have to carefully hoard my remaining video monitors! ;-) Thanks to everyone who helped me work this out... Noel

8 years, 1 month

Programming for the Alto's Mesa

by lproven＠gmail.com

>From the discussions around Y Combinator's Alto restoration... (Some may not know that the founder of Y Combinator is Paul Graham, using some of the money Yahoo! paid him for Viaweb, which became Yahoo Stores. PG is a Lisp champion and evangelist.) The Alto restoration is being discussed on Hacker News, Y Combinator's very successful forums: https://news.ycombinator.com/item?id=11929396 This comment struck me: ? Animats 2 days ago I just looked in some boxes I haven't opened in decades. I have "Mesa Language Manual, Version 5.0, April 1979". If the people with the Alto need this, let me know. If the world had used Mesa instead of C, computing would have been far less buggy. Mesa was a hard-compiled language, but it had concurrency, monitors, co-routines ("ports", similar to Go channels), strong type safety, and a sane way to pass arrays around. In the 1970s. (I should donate this stuff to the Computer Museum. I just found the original DEC Small Computer Manual, many 1960s UNIVAC mainframe manuals, and a reel of UNIVAC I steel magnetic tape.) ? I knew that the original Smalltalk boxes weren't Smalltalk all the way down to the metal, and that there was an OS and language, Mesa, underneath... but I didn't know it was used for anything much *else* or that some considered it important. Anyone here know or remember Mesa? I'd like to hear more about it. -- Liam Proven ? Profile: http://lproven.livejournal.com/profile Email: lproven at cix.co.uk ? GMail/G+/Twitter/Flickr/Facebook: lproven MSN: lproven at hotmail.com ? Skype/AIM/Yahoo/LinkedIn: liamproven Cell/Mobiles: +44 7939-087884 (UK) ? +420 702 829 053 (?R)

8 years, 1 month

Sun4 370 PSU Maintenance/Schematics

by aswood＠t-online.de

Hello all, I do have an Symbolics UX1200 plugged into a Sun4 370 host. Before powering the host, just to be secure, I'd like to check the psu - or if the psu will be broken, I'd like to try to fix it. Yesterday I'd a look into the psu - very complicated layout! Is there any known documentation, servicing and maintenance documentation or schematics for psus used in Sun server/workstation available, of course esp. for psus used in Sun4 370 systems? -- Andreas ?

8 years, 1 month

Programming for the Alto's Mesa

by jnc＠mercury.lcs.mit.edu

> From: Josh Dersch >> ISTR that BravoX was written in Mesa. -- Ian > Yes it was, as was MazeWar ?? There was a MazeWar on the Alto, early on, and I'm not sure that version was in Mesa. Maybe someone re-implemned it in Mesa for some of the later machines? (Of course, all the Xerox ones were inspired by the much earlier Imlac one.) Noel

8 years, 1 month

FPGA I/O and external memory (was Re: CDC 6600 emulation - was Re: How do they make Verilog code for unknown ICs?)

by spacewar＠gmail.com

On Mon, Jun 20, 2016 at 10:07 PM, ben <bfranchuk at jetnet.ab.ca> wrote: > Do you use Static or Dynamic ram with the FPGA's? I've done both. You indicated that you wanted 5V I/O. AFAIK, there haven't been any new FPGAs made in many years that have even 5V-tolerant I/O, let alone actual 5V I/O. Some really old FPGAs may still be in production, but are not very cost-effective. The latest midrange to high-end FPGAs aren't even 3.3V-tolerant. However, the economy FPGAs such as Spartan 6 and Artix 7 still support 3.3V I/O, and are quite inexpensive for the amount of resources provided. For 5V-tolerance, it is usually adequate to use 3.3V I/O with series resistors to limit the current. Xilinx specifies a maximum rated current for the clamp diodes. This works fine when interfacing actual TTL (or TTL-compatible MOS) parts. It is NOT adequate for driving 5V CMOS, such as CD4000 series, because the FPGA won't drive above 3.3V, and the 5V CMOS inputs typically are specified for Vih min of 90% of Vdd, which is 4.5V. The series resistor does slow down the signal, which usually isn't a problem with TTL since TTL is quite slow by FPGA standards. Where it is a problem, an nFET voltage clamp can be used instead.

8 years, 1 month

How do they make Verilog code for unknown ICs?

by wkt＠tuhs.org

All, I messed around with VHDL last year. I found this a great book to learn VHDL best practices: http://www.gstitt.ece.ufl.edu/courses/eel4712/labs/free_range_vhdl.pdf The book is free but you can also buy a printed copy at http://freerangefactory.org/ I started with GHDL: https://www.fpgarelated.com/showarticle/20.php and then progressed to a Nexys4 FPGA board. Lots of fun. Just a few more resources to add to the mix. Cheers, Warren P.S The CPU I built with it: http://minnie.tuhs.org/Programs/UcodeCPU/index.html

8 years, 1 month

NetBooting old MacOS 8.x or 7x.

by swiftgriggs＠gmail.com

Due to the news about the MacOS name change, it's becoming quite hard to Google for older MacOS stuff. Was it ever possible to netboot MacOS 8.1 or earlier? I have A/UX 3 running nicely on a Quadra 700, now, but now I want to dual boot it with MacOS, but I don't have a CDROM. Taking out the drive and putting it on my other 68k Mac (a Centris 660AV) and installing MacOS still gives me some weird issues that I suspect are related to having installed it on different hardware. If I can't do a network based install, I'll probably just steal a longer SCSI cable, use a molex power splitter to add another 5V power cable, and then install from CDROM while the system is half-open. Then I'll just button it up afterwards. The factor SCSI cable in my Quadra 700 has only one connector for a drive. -Swift

8 years, 1 month

General *NIX ramble thread - was Re: Quadra 660AV what's with the "PowerPC" label?

by ian.finder＠gmail.com

Changing thread title and invoking filter. Thanks, - Ian On Mon, Jun 20, 2016 at 10:50 AM, Swift Griggs <swiftgriggs at gmail.com> wrote: > > And yet, now that significant chunks of the Linux underpinnings are > > being combined into one purpose-written close-knit chunk, designed by a > > single team, the same sort of people that praise *BSD for its conceptual > > unity are harshly damning the thing bringing comparable unity to Linux. > > Odd, that. > > It's not the same thing, IMO. People aren't slamming Linux+systemd for > unifying their team (I've not even seen the harshest systemd critics > mention this even in passing). They aren't upset because of the greater > "conceptual unity", either. They are upset because it's breaking faith > with "the unix way" (creating a giant all-consuming mega-daemon with > equally heinous binary opaque supporting-crap ala journald) and going > their own way (a hard right toward Bloatville with a couple of stops near > Lake Clueless if you ask me), and they are, in the opinion of many, being > jerks with the implementation of their planned schism. > > -Swift > > -- Ian Finder (206) 395-MIPS ian.finder at gmail.com

8 years, 1 month

DL11 M7800

by jnc＠mercury.lcs.mit.edu

> From: Paul Birkel >> I will upload the content to the CHW (and add the DB9 pinouts, too). > Yes, please. OK, done; see: http://gunkies.org/wiki/DEC_asynchronous_serial_line_pinout and it references the new: http://gunkies.org/wiki/EIA_RS-232_serial_line_interface I'd be grateful for any feedback on how I can improve the page(s) - more data to add, thinks to explain better, etc. Note: I added the DB9 pinouts, _but_ I have never made an actual DEC->DB9 cable, and am unlikely to (see below), so these have not been experimentally tested. I'm pretty sure they're right (I checked them against some online tables), but 'the difference between theory and practise', etc, etc. So if someone does make any DB9 cables from this page, and can confirm that they works, I'd be very grateful! :-) I personally don't recommend making DEC->DB9 cables. DB25P<->DB9S adaptors are cheap and easy to find on eBay, and if you make everything DB25, all you'll need are a few DB25P<->DB9S adaptors to connect to PCs, and all your other cabling activity (e.g. connecting one PDP-11 to another) will be simple, since everything will be standardized on DB25s; no having to keep two kinds of every cable. Noel

8 years, 1 month

Eckert - Faster, Faster; books in general

by thebri＠gmail.com

Is there an electronic copy of this floating around? My (ex-library) copy is missing all of chapter 11, "What is there to calculate?. (And the last page of the previous chapter). The pages weren't ripped out, they were missing when it was bound. Very annoying, I enjoyed the book right up until it crashed, so to speak. Two, also ex-library, copies are listed on Amazon, and I hesitate to get another copy with the same problem. There are others, of course, at outrageous prices. Or maybe I don't realize the significance of '1st edition, not ex-library'. Just to make any discussion a bit more interesting, what would you suggest along similar lines? The two giant books on IBM (detailing "pre-360", and "360") were quite fun too. bri

8 years, 1 month

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test-drb June 2016