test-drb

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101090 discussions

by john_a_s2004＠hotmail.com

Thanks, yes a schematic would be great. Can I post it to the web please? I'm sure Tony knows the following, included as background. Here's the adapter I used to read the 2564 in a 2764 programmer: 2564 pins?????? 2764 pins 20 (A11)??????? 23 (A11) 23 (A12)??????? 2 (A12) 2+27(CS1+CS2)?? 22 (OE) 1 (Vpp)???????? 28 (Vcc) 22 (PD/PGM)???? 20 (CE) (NC)??????????? 27 (PGM) All other pins connected straight through. The above can't be always used in the reverse direction (eg using a 2764 in a 2564 socket), as CS1 and CS2 may or may not be tied together depending on the circuit. Also programming a 2564 uses a different algorithm to programming a 2764. For example, on a 2764 Vpp can be left at programming voltage of 21V during a verify cycle, whilst on the 2564 Vpp is at 25V for programming and 5V for verifying / reading (I assume the 25C64 is similar but with a lower Vpp). Regards, John ============================================================== Tony Duell ard at p850ug1.demon.co.uk Mon Oct 11 15:29:35 CDT 2010 > I've finally made an adapter to read the 2564 on my programmer (which can o= > nly read the 2764). There were about 5 pins to rewire=2C I'll write some no= > tes later on the differences. > > I've upload the ROM image to: > > http://www.vintagecomputers.btinternet.co.uk/mw4/mw4.zip THanks. I've downloaded it, it unpacks OK. I wondered why the file was larger than ecxpected, but then saw you'd included both hex and binary images. I will probably burn it into a 27C64 (those I have, and my programmer can easily handle them) and make an adapter to use it in the MW4. Then we can see if that gets mine working. I won't be doing this just yet (I've gor various other things to do), but I will let you know how I get on when I do do it. If you are going to disassemble the ROM, do you need schematics of the MW4 hardware? -tony

15 years, 6 months

IP Fragments - Worth doing, testing strategies?

by bqt＠softjar.se

On 10/01/10 00:22, "Michael B. Brutman" <mbbrutman-cctalk at brutman.com> wrote: > Sean Conner wrote: >> > While I'm familiar wih IP, I haven't tried implementing it, but, what if >> > you were to set an MTU size of around 50 bytes? The IP header (sans >> > options) is 20 bytes, and the TCP header is another 20. I would think >> > setting the MTU to just above 40 might cause some fragmentation (I thought >> > of suggesting an MTU of just above 20, but then you're testing for IP >> > fragmentation, and not TCP fragmentation. >> > >> > I tend to do stupid stuff like that, but then again, I*was* hired to >> > write testing code at my current job ... >> > >> > -spc (In thoery, IP should work with an MTU of 30 bytes, right?) > The IP header is 20 bytes without any IP header options, and the TCP > header is another 20 bytes without any TCP header options. The minimum allowed MTU is actually 68. (I wrote 65 erronously in a previous mail.) See RFC 791, page 24. In addition to the 68 bytes for a single fragment, an IP stack must be able to handle 576 byte packets, but there is no requirement that this isn't sent in fragments. The receiver must, however, always be able to handle atleast 576 byte packets. > My implementation has room for 10 fragments per packet (configurable > with a #define), which is great for a 'normal' MTU size. If I tested > with a ridiculously small MTU it would wind up throwing a lot of things > away, but many implementations do the same thing. You should allocate that stuff dynamically. > My fragment problem is mostly on the source side - the source machines > are too clever about trying to probe and eliminate fragments. > > Linux has also been 'interesting' as a gateway. Some kernel versions > allow TCP fragments through even though they have bad checksums. I > throw away any packet with a bad checksum. Mixing NAT (Network Address > Translation) and fragments was problematic in my setup too - I think > that Linux was completely screwing up the payload checksums for TCP. What are you talking about? IP fragments for TCP don't have checksums of the TCP payload. There is only a checksum for the IP header. Only the final destination reassembles the packet, and can do a checksum of the TCP packet. Johnny

15 years, 6 months

Seagate ST39173N 9.1GB Narrow SCSI Drive failure

by mark＠wickensonline.co.uk

Hi, Apologies that my first post to this list for a while is one requesting assistance, but my unjustified faith in hard drive technology has bitten me... The Seagate drive in my VAXstation 4000/90 (running OpenVMS 7.3) failed recently and it hadn't been backed up for quite a while. We had a power surge which tripped the main circuit breaker, and when I reset the breaker and turned the box back on the drive failed to spin up. The drive is recognized by the firmware, except that the capacity column shows ... instead of a figure. An LED on the controller circuit board lights a couple of times reinforcing that the drive electronics are talking across the SCSI bus, but as I say the drive refuses to spin up. The box was running a website dedicated to HECNet (it was at http://www.hecnet.eu) using the WASD webserver and was able to report on issues with the network and current HECnet nodes. My (limited) diagnostic skills would point towards a drive motor controller failure, or less likely sticking heads. Given that the drive has been powered down and up on a number of occasions without issue I'm thinking it is probably a controller failure rather than a head problem, but I'm open to alternative opinions. Does anyone have a Seagate ST39173N drive they would be prepared to part with for a reasonable amount of money? At the moment the only drives I can find are in the region of $150 which is more than I can comfortably part with on the off chance that swapping the controller board might give the drive new life. Many thanks for the help. Mark.

15 years, 6 months

Old calculators

by charlesmorris800＠centurytel.net

I have more calculators accumulated over 30+ years than I'll ever play with, so would like to find new homes for a few. http://i1181.photobucket.com/albums/x426/DrCharlesMorris/PA030021.jpg >From left to right: -RadioShack EC-220 (Cat No 65-604). Working. -Unitrex "Memory-8". Missing battery compartment cover. Working. -Commodore MM2 "Minuteman 2". Not working. Comes with wall wart. -TI SR-51-II. Not working. Several years ago I put new nicads in the battery pack and it worked then. With case, wart & manual. -Unknown mfg. "4-banger" with LCD display and incandescent backlight. Works but has air bubble partially obscuring LSD's 2/3. This one was written up in "73 Magazine" in the late '70's or early '80's and was available from Meshna, Poly Paks or a similar surplus place. Would like to get $10 for all five, plus shipping from US zip 65775.

15 years, 6 months

at&t unix pc (big black binder scan)

by mtapley＠swri.edu

At 5:34 -0500 10/12/10, Mark D. wrote: >If Al could send me the guidelines, I'll happily see what I can do. At 5:34 -0500 10/12/10, Alexandre quoted Dave: > > I for one would thank you wholeheartedly. > > Make that two :) ...three! -- - Mark 210-379-4635 ----------------------------------------------------------------------- Large Asteroids headed toward planets inhabited by beings that don't have technology adequate to stop them: Think of it as Evolution in Fast-Forward.

15 years, 6 months

VTL/Dutchess logic

by h.j.stegeman＠hccnet.nl

Hi, VTL stands for Vendor Transitor Logic. I (finally) found it in a S/34 hardware manual. VTL is Texas Instrument TTL chips with IBM part numbers. Henk www.ibmsystem3.nl

15 years, 6 months

OT : RJ45 Telecom wiring

by ard＠p850ug1.demon.co.uk

Can anyone suggest URLs, etc that give the wiring of RJ45 sockets. in telecom applications. Not 10bse<n> (which from what I understand are not strictly RJ45's anyway), or ISDN, but older telecoms. The web pages I've found soe far give the wiring for up to 4 POTS lines on an RJ45, which is, again, not what I am looking for... In particular : What pins would I expect to find a normal 'switched' telephone line on (4 and 5, I think?) What about a 2-wire leased line ('private circuit')? Or a 4-wire one? Why would there be a resistor of about 866 ohms connected between pins 7 and 8? Why would pins 3 anf 6 be shorted together? In case anyone's wondering, I've bought a non-working telephone line simulator, and am trying to make sense of the numerous relays connected to the telephone connectors, which are RJ45s (genuine RJ45s, with the extra polarisation notch). Books on US telcoms practicce are few and far between over here... Thanks in advance for any help... -tony

15 years, 6 months

Microwriter MW4 help

by john_a_s2004＠hotmail.com

Hi, John S <john_a_s2004 at hotmail.com> wrote: >>> I recently obtained a Microwriter with an LCD display. >>> >>> Else it may be faulty >>> I found Tony's post from 2009 asking for a 'good' EPROM image maybe >>> mine is failing in a similar way. > >Tony wrote: >> FWIW, I am still stuck... I am pretty sure the Firmware EPROM in mine is >> corrupted, some 'chords' do not produce the characters I would expect >My one can generate all the letters, numbers and punctuation marks so fingers crossed the EPROM is>OK. >> IIRC, the EPROM is a 25C64 (which is slightly different to the more common >> 27C64). If you have a programmer capable of reading out that device, it >> would be interesting to compare the ROM in mine with it. >OK, I'll try and read the EPROM. This might take me some time, but I am keen to >do it as there is very little technical stuff about the MW4 on line. I've finally made an adapter to read the 2564 on my programmer (which can only read the 2764). There were about 5 pins to rewire, I'll write some notes later on the differences. I've upload the ROM image to: http://www.vintagecomputers.btinternet.co.uk/mw4/mw4.zip The file looks OK, but there are a lot of FF bytes on the ROM, which hopefully imply that the whole 8K bytes weren't needed rather than the ROM is faulty. Hopefully Tony can compare this with his ROM and come back with any further tips or questions. >I might try and disassemble the code too Not yet tried DASMx <http://myweb.tiscali.co.uk/pclare/DASMx/> (thanks for the link Phil), maybe one day. Regards, John

15 years, 6 months

The "death" of GEOS

by christian_liendo＠yahoo.com

Interesting read since I haven't played with GEOs for a couple of years now. I know people who still used GEOs for the C64, but the PC version has been in limbo for a while http://www.osnews.com/story/23882/The_Death_of_GEOS_

15 years, 6 months

Monrobot

by evan＠snarc.net

Does anyone know of a good history, online or in print, regarding the Monrobot computers? I found some technical info at Bitsavers and on Ed Thelen's site, but I'm looking for info about the people behind the company in the 1950s.

15 years, 6 months

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