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101090 discussions

Commordore 64 character color cycling (Ethan Dicks)

by tpresence＠hotmail.com

> > The Color SRAM is a 2114. Very ordinary and, in my experience, prone > to failure. > > If you have another C-64, you could try swapping the PLA. You will > need an 18-pin socket for the SRAM. The chips are available from a > number of surplus places like Unicorn Electronics, BG Micro, and more. > Speed ranges for the 2114 are, IIRC, 250ms-450ms. I don't remember > what speed the C-64 requires, but you can typically sub a faster chip > than the circuit requires. > > -ethan I have already purchased a replacement sram for the 2114 (acutally 2 of the units, one P2114 and one MM2114N-2) and intend to replace the IC sometime today. I do have another C64, but no chips are socketed, and I don't want to ruin it, thus I'll just try replacing it in the bad unit. My understanding is that I need a chip that has a speed faster than half a machine cycle for the system to work properly. The spec sheet on the P2114 states that it has a 450ns access time. For the MM2114N-2 it looks like its 200ns. I understand that the access speed requirement is .5*(cpu freq/1)/machine-cycle. I don't know the machine cycle for this operation, but assuming the worst with an IC having an access time of 450ns, the machine-cycle couldn't be over 2.25 for things to be ok. If I use the 200ns IC, I should be good with a machine-cycle of just over 5. I could probably solve this by opening up the unit and just pulling the IC scribe marks and looking up the data sheet, but the location with the ICs is 50 miles from the house, and I happened to be nearby yesterday...so I just winged it. Can anyone checksum my thoughts here? Is my algorithm and its implementation ok? I also bought a replacement for the PLA, however, I had misunderstood the requirement. I thought it was just a plain ole N82S100, but now I understand that it is a specially programmed N82S100. Although I have found a ROM file I could perhaps burn on the chip, I simply don't have the gear. I'm hoping this isn't the problem, as I have to mail order the part, but I understand that this is the most common IC to fail on the C64 board. Since I'm getting only character color palette cycling, and have a border and don't have a problem with a blank screen, I am encouraged that this IC is probably ok. Just to be safe, I bought a replacement for U29, as the description in the c64 chip and common problems guide has content that really looks similar to my problem, moreso than even the description for problems with U6 (the 2114). Thanks for your commentary though. I'm likely to buy sockets for these chips as well, as they aren't that expensive, and it may save me issues should the selection I made be suboptimal. Kevin

14 years, 3 months

Well, that's depressing.

by derschjo＠mail.msu.edu

eBay item 320840589826. I suppose if anyone's looking for a Symbolics Ivory 2 CPU to play around with (LispM on a chip) here's your chance. Sad to think about all the machines these came out of... - Josh

14 years, 3 months

C compilers and non-ASCII systems

by jonas＠otter.se

At 11:21 AM -0500 1/31/12, Sean Conner wrote: > > So now I'm wondering---besides Baudot, 6-bit BCD and EBCDIC, is there any > >other encoding scheme used? And of Baudot, 6-bit BCD and EBCDIC, are there > >any systems using those encoding schemes*AND* have a C compiler available? > > Not sure what you mean by 6-bit BCD? For current systems which use a 6-bit character code, the Unisys 1100/2200 class systems (ClearPath nowadays) use Fieldata as well as 9-bit ASCII. They have a C compiler. These machines are 36-bit, so to fit ASCII characters in, they extended the characters to 9 bits, fitting 4 "ASCII" characters in a word instead of 6 Fieldata characters. It is possible to use all 9 bits which creates interesting problems when you need to migrate the code to a different architecture. I have come across (ancient but "modernised") applications which mix Fieldata and 9-bit ASCII... Also IIRC there is no reasonable way to handle Fieldata in Unisys C, so you have to treat Fieldata characters as hex or octal values. /Jonas

14 years, 3 months

off topic? Signetics chips 10K ecl chips available

by useddec＠gmail.com

Starting to go through some smaller boxes and found a few thousand Signetics 10100 - 10175 chips. all sorted (pretty much) bulk. and some hard to find. Date codes are mostly around 1978. I would like to sell in as large a lot as possible or maybe variety packs. I have 3 or 4 gaylords of small parts,mostly chips,and it's going to be a slow. process. The company I got this from was a board repair depot, and also repaired core memory boards. Please feel free to contact me off list with any questions. shipping fron 61853. Thanks, Paul

14 years, 3 months

Visiting Bristol UK

by huw.davies＠mail.vsm.com.au

I'm yet again visiting Bristol UK for most of January 2012. I guess during the week I'll have to attend the training course that work is sending me to, but I wondered if anyone had any classic computer recommendations for the weekend? Assuming the weather is OK, I'm happy to drive a reasonable distance but local stuff is easier. I did Bletchley Park last time I was in the UK (November 2010) and I've already promised myself that I'll visit the SS Great Britain and the Newport cable bridge, but wondered if there were other CC related things in the area. If anyone in the area wants to catch up for a beer, I'd happily shout a pint of the local bitter. Huw Davies | e-mail: Huw.Davies at kerberos.davies.net.au Melbourne | "If soccer was meant to be played in the Australia | air, the sky would be painted green"

14 years, 3 months

C compilers and non-ASCII systems

by tshoppa＠wmata.com

IBM has a very handy page on C compatibility with EBCDIC system services: http://www-03.ibm.com/systems/z/os/zos/features/unix/bpxa1p03.html

14 years, 3 months

C compilers and non-ASCII systems

by cym224＠gmail.com

On 31 January 2012 12:21, Zane H. Healy <healyzh at aracnet.com> wrote (in part): >> And of Baudot, 6-bit BCD and EBCDIC, are there >> any systems using those encoding schemes *AND* have a C compiler >> available? z/OS is not only POSIX, it is UNIX (see http://www.opengroup.org/openbrand/register/brand3470.htm). (Sorry for not replying to the OP -- I just saw this now.) N

14 years, 3 months

Looking for Andrew Back

by dbetz＠xlisper.com

Does anyone here know how to contact Andrew Back? I have some equipment to send him and I need a mailing address. Thanks, David Betz

14 years, 3 months

Repairing a TI-1270 calculator

by jgessling＠yahoo.com

Thanks Tony.? As you suggested there are 10 wires connecting the main board to the keypad.? As in 4 x 6.? I fiddled around a little, gently.? I've ruined another similar unit by cutting those wires in hopes of reattaching them so I was avoiding that.? I guess I made something that was loose become a circuit at least for now.? I works great.? Really a treat to see it work.? Maybe not an HP, but they rarely break anyway. Jim

14 years, 3 months

Commordore 64 character color cycling

by tpresence＠hotmail.com

I have a malfunctioning C64 that I would like to repair that is exhibiting the most odd of behaviors. The system operates fine, except displayed fonts cycle through the color palette. If you remember the old atari 2600 game "Adventure" its behaves like the chalice does, every second or so changing colors. I haven't started probing the system at all, and although I can use a soldering iron, my troubleshooting skills are pretty rusty. I was considering this a good project for a refresher. Sound doable, or is it likely I'll be looking to replace lots of components on the board? Kevin

14 years, 3 months

C compilers and non-ASCII systems

by cctech＠beyondthepale.ie

At 11:21 AM -0500 1/31/12, Sean Conner wrote: > A friend recently raised an issue with some code I wrote (a hex dump >routine) saying it depended upon ASCII and thus, would break on non-ASCII >based systems (and proposed a solution, but that's beside the issue here). >I wrote back, saying the code in question was non-portable to begin with >(since it depended upon read() and write()---it was targetted at Posix based >systems) and besides, I've never encountered a non-ASCII system in the >nearly 30 years I've been using computers. > > So now I'm wondering---besides Baudot, 6-bit BCD and EBCDIC, is there any >other encoding scheme used? And of Baudot, 6-bit BCD and EBCDIC, are there >any systems using those encoding schemes *AND* have a C compiler available? > > -spc (Or can I safely assume ASCII and derivatives these days?) A unix called UTS (Universal Time Share?) by Amdahl ran (amongst other things under VM) on an Amdahl 5870 I worked with in the early 1990's. This was an EBCDIC machine. I never did much with UTS but I'm pretty sure it had a C compiler. There was also C/370 for VM/CMS and MUSIC. Regards, Peter Coghlan.

14 years, 3 months

Evil Plan

by john＠yoyodyne-propulsion.net

Mr Zoidberg, Thank you for bringing that error to our attention. John Stupid John (or web designer) has met with an unfortunate accident. On Tue, Jan 31, 2012 at 11:25 AM, <quotes at nospam.com> wrote: > First Name: JohnA > Last Name: Zoidberg > Email: cctalk at classiccmp.org > > City: > State: > Zip: > IP: xxx.xxx.xxx.xxx > Evil Plan: Your logo says "Yoyodyne Propolsion Systems", not "Yoyodyne > Propulsion Systems" > -- Yoyodyne Propulsion Systems: "The Future Begins Tomorrow" Visit us at: http://www.yoyodyne-propulsion.net -------- "Yes, Obama duped young people by not doing every single thing they want. So now, they'll all vote Republican. It's like when I want some bread, I won't settle for half a loaf. Instead, I will have a muffin made of broken glass." -Stephen Colbert

14 years, 3 months

Commordore 64 character color cycling

by dm561＠torfree.net

Original Message: Date: Mon, 30 Jan 2012 11:59:44 -0700 From: Kevin Reynolds <tpresence at hotmail.com> > I know following up your own request is kinda taboo, but I should have > shared more information... > I am guessing that the problem is with the Color RAM (SRAM) in slot U6. > This model of C64 has socketed components, but I am not sure U6 is one of > these. The other possible issue is PLA U17. As the problem never goes > away, perhaps it is more than this. > Is there a good vendor to get replacements this late in the game? > Kevin Try here: http://www.arcadecomponents.com/catalog/item/3054735/8335676.htm

14 years, 3 months

Troubling Olivetti M24 Monochrome Monitor

by hendrikvandewerken＠gmail.com

Since a few days the monitor of my Olivetti M24 displays a bright spot in the middle of the screen when the system is switched off. I suspect the screen will be soon damaged this way. I know there is a circuit in CRT monitors that prevent this. But I don't know where to look on the circuitboard. I did check the parts on the print on the tube base: they seemed to be alright, so now I'm stuck. Does anyone has a clue for me how to proceed?

14 years, 3 months

Opening the Mac M0001 case

by wheagy＠gmail.com

I allowed the case to sit overnight, and when I tried it again today, it came apart much easier...about like I expected. The floppy mechanism was definitely gummed up. It didn't appear to be damaged so I lubed it and reassembled and it works great again. Thanks for the info. Win > Something happened to the floppy drive. It worked fine for a long time, but now will not allow a disk to be fully inserted. It goes it about all but the last quarter inch. I can't see the problem by looking through the slot, so it looks like I need to get inside. The case just seemed much harder to open than I expected, so I wanted to make sure I didn't break anything. I'll be careful to stay away from the high voltage innards. >That's quite a common issue on the original 'auto-inject' drives. They were greased with this god-awful white grease stuff that turns to gooey sludge over the course of time and jams the mechanisms. Best advice is to remove it, see if it's physically damaged (I've had parts bend in them when they jam) and if it seems okay clean and re-lube the mechanism and see if you can get it moving again.

14 years, 3 months

Apple II Colour Demodulator

by thrashbarg＠kaput.homeunix.org

Hi, This might interest someone here, so I thought I'd post it. I've been working on a colour demodulator for my Apple //c. It converts the output to component video suitable for any television with component inputs. The original composite output of the //c becomes the luminance input and the circuit extracts the red and blue difference signals. It's not 100% perfect but it does display colour that mostly resembles the original NTSC colour palette. http://kaput.homeunix.org/appleii or http://kaput.retroarchive.org/appleii If you have two MC1496's, feel free to build it. I'd like to see if it works unmodified (or with any modifications) on an NTSC model Apple ][ or //. The reason why I made this is because I don't have a PAL modulator for my //c. My television does support NTSC, but the Australian version of the machine doesn't output the correct timings for NTSC... it was designed to be attached to the PAL modulator. Cheers, Alexis.

14 years, 3 months

11.98135 MHz crystal applications

by fraveydank＠gmail.com

Anyone know what this frequency is for? I have a crystal in my bin of pulls, no idea what I pulled it from (my guess would be an old dead ISA modem or sound card, given where most of my pulls came from). It doesn't divide nicely into NTSC or PAL color subcarriers (my normal assumption for weird frequencies), but it it's still a pretty common part. The one place I found it mentioned that wasn't a datasheet site had something (maybe) to do with DTMF decoding: http://ohlandl.ipv7.net/communications/Gammalink.html Any ideas? - Dave

14 years, 3 months

Looking for 8080/Z80 BASIC

by dm561＠torfree.net

----- Original Messsage: Date: Fri, 30 Dec 2011 22:43:21 -0800 From: Josh Dersch <derschjo at mail.msu.edu> Anyone have any recommendations for a reasonably featured 8080 or Z80 BASIC? What I've got running at the moment is a mongrel IMSAI 8080 with a Z80, 48K of working memory and a serial port. My eventual goal is to get CP/M running on it (I have a Cromemco 64FDC -- anyone know of either an official CP/M for this or know of a BIOS that supports this controller before I start writing my own?) but for the time being I thought it would be fun to get a BASIC running on it. <snip> Thanks, Josh ----- Reply: Just curious: Does your memory configuration support swapping out the RDOS boot/monitor ROM? And what drive(s) do you have connected? As you probably know, the FDC supports 5.25"DD as well as 8" and the 3.5 and 5.25" HD equivalents. I haven't seen any standalone BASIC versions for the FDC; there are at least two versions of BASIC for the Cromemco, but AFAIK they both require a bootable CDOS disk. However, unless they use any of the extra calls in CDOS I wouldn't be surprised if they worked just as well with CP/M. In addition to Cromemco's CDOS CP/M equivalent AFAIK there were also at least two official third-party CP/M implementations for the FDC and one or two hacked BIOSes, but there may be compatibility issues among the three different versions of the FDC. Interesting though; I'll have to look around...

14 years, 3 months

Opening the Mac M0001 case

by wheagy＠gmail.com

HI, Can someone give me the Cliff Notes version of opening the M0001 case? I removed the five screws from the back (including the two deeply recessed screws) but the case is just as tight as when the screws were in. What am I missing? Thanks...Win wheagy at gmail.com

14 years, 3 months

Starting point for diagnosing unhappy Commodore 1581 drive?

by derschjo＠mail.msu.edu

As if I needed another project, I picked up a 1581 yesterday at SRCS in unknown condition. Hopefully this won't distract me from my Cromemco floppy issues for too long :). The power switch was broken (permanently stuck in the "off" position) so I replaced it with one from a "parts" C-64. Once that was repaired the symptoms I'm seeing are: - Both LEDs on the front come on and stay on permanently. My understanding is that the access light should turn off after about two seconds. - If the drive is hooked up to my C128 at powerup, the 128 will hang after displaying the startup banner (I assume it's waiting for a response from the drive and not getting one...) - If a disk is in the drive, the disk will spin for a second or so and the heads will seek back to track zero. The last item makes it seem like the 6502 is running and that the EPROM contents are still valid. I dumped the EPROM and verified that its contents are correct against an image from the 'net. The power supply is a known-good & tested supply I've been using with a 1541-II. 5V and 12V supplies look fine. For good measure I've cleaned the sockets & pins for the EPROM and the WD1772 (the only two socketed chips). Anyone have any tips for narrowing down the fault before I start digging through the source listings & schematics? Thanks as always, Josh

14 years, 3 months

Opening the Mac M0001 case

by wheagy＠gmail.com

>How easy it comes of depends wether it's been removed many times before. First time removals >can be tight as hell. >Might I ask why you are removing the case bucket? Mark, Something happened to the floppy drive. It worked fine for a long time, but now will not allow a disk to be fully inserted. It goes it about all but the last quarter inch. I can't see the problem by looking through the slot, so it looks like I need to get inside. The case just seemed much harder to open than I expected, so I wanted to make sure I didn't break anything. I'll be careful to stay away from the high voltage innards. Thanks...Win

14 years, 3 months

Repairing a TI-1270 calculator

by jgessling＠yahoo.com

I've gotten one of these beauties, a lovely pumpkin orange overlay around the keys.? Inserting a battery, it's pretty good? but the 4 and the 6 key just don't work. I took it apart thinking it's a stuck or rusty key but pushing just on the raw Kilxon keypad it's still the same.? I suppose there is some kind of keyboard scanning going on that's not picking up these pushes even though the actual buttons do work.? My previous experiences of opening similar TI thing have been just disastrous.? The keypad is connected to the logic board by 8 or so hard wires that are looped around to fold it into the case. If anyone has any advice on this please let me know.? Thanks, Jim

14 years, 3 months

6502 S-100 Board Writeup on S100Computers.com

by LYNCHAJ＠YAHOO.COM

Hi! The S-100 6502 CPU boards are with their builders and seem to be working. John has written up a page on S100computers.com on bringing up the S-100 6502 CPU board. http://s100computers.com/My%20System%20Pages/6502%20Board/6502%20CPU%20Boar… We are incorporating the changes necessary for S-100 6502 CPU board V2 to be IEEE-696 compliant with TMI circuitry. The changes necessary are quite extensive. However, if other builders would like to make further changes please contact me. There is a large prototyping area on the V1 board to support the new circuitry. The schematics, PCB layout, parts list, and test software other information is on the N8VEM wiki http://n8vem-sbc.pbworks.com/w/browse/#view=ViewFolder <http://n8vem-sbc.pbworks.com/w/browse/#view=ViewFolder&param=S-100%206502%2…> &param=S-100%206502%20CPU%20board%20V1 There are still plenty of the S-100 6502 CPU board V1 PCBs left so if you would like one or more please contact me. They are $20 each plus $3 shipping in the US and $6 elsewhere. Thanks and have a nice day! Andrew Lynch

14 years, 3 months

all this talk of Intertec, anyone have a Headstart?

by chrism3667＠yahoo.com

preferably one I can coerce you to sell :)

14 years, 3 months

LA36 available in Ann Arbor

by mta＠umich.edu

Does anyone want a Decwriter LA36? I've got one that I'm willing to give to anyone who will come get it (or pay for shipping, although that would be expensive). As far as I know it works although it hasn't been used in years. The one problem I know of is that the 20 mA interface was blown out in a lightning storm sometime in the 70s, but the EIA interface worked the last time I tried it. I think I also have some (perhaps all) of the user and maintenance manuals for it. I also have an acoustic coupler if you want the true 1970s experience. This is located in Ann Arbor, MI so it would be easiest for someone in southern Michigan or northern Ohio or Indiana to come get it. Mike Alexander

14 years, 3 months

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