test-drb July 2006

test-drb@ccmp.vtda.org

204 participants
377 discussions

by ajp166＠bellatlantic.net

> >Subject: Re: OMTI parallel port interface hack > From: ard at p850ug1.demon.co.uk (Tony Duell) > Date: Sat, 08 Jul 2006 22:44:30 +0100 (BST) > To: cctalk at classiccmp.org > >> > The problem is that the 8255 is fundamnetally broken as designed (well, >> > I'd expect that from Intel, alas). Any write to the mode control register >> > clears all outputs to 0's. Which means you can't reverse the direstion of >> > one of the 8 bit ports without mucking up everything else. >> >> Oh really? I've never heard _that_ before about these parts... Do you know > >It is mentioned in the Intel 8255 data sheet. > >> offhand if that's the case for other brands as well? I believe I have some >> NEC parts around somewhere. It applies to ALL 8255s. For some uses this is not a problem, others just plain annoying. All a side effect of putting 10# in a 5# bag if you ask me. However of all the parallel devices it's widely available (even in CMOS) and despite it's flaws it's still more versitile than any other PPI. An alternate if the application can tolerate it's interface is the 8155 (22 IO lines and 8085/8088 muxed data/address interface). >It certainly applies to the National Semiconductor version. I used one in >my first Z80 homebrew, and one of the first programs I wrote once I'd >added it simply configured all ports as outputs, wrote a suitable value >to port A, then jumped back to the start. I then found the lines that >should be high were, in fact, pulsing. Reading the data sheet showed why >(I was re-loading the mode control register, thus clearing the output >ports). Of course it was trivial to correct in this program, but it sure >made life difficult later. Once you know this it's less a problem. Hint: if you invert the outputs and add pullups you can hide the problem for some cases. For many apps it's not a problem. The upside is 24 IO lines. Or two ports with full handshake and interrupt posting. No so bad really. For some cases using the 8255 is way overkill and a LS273 was more suitable but then I'm barking at the design of others. Allison > > >-tony

18 years, 5 months

post for paul about vcf gear

by jwest＠classiccmp.org

I'm posting this for Paul Anderson, as his mail server is apparently currently blacklisted by spamhaus. > I have the following list of booklets I am considering making copies of to > take to VCF/Midwest next week. I'll be going to Kinko's or somewhere > early > next week and am trying to figure out the level of interest. These were > made > up for DEC field service only. I'm guessing $20 each, except for the PDP11 > which is about 100 pages. If anyone wants them mailed within the US, $5 or > $6 should cover shipping for the entire set. Please contact me off list if > you have any interest or questions about this, or if you want anything > else > brought to VCF/ Midwest. > > > > RK05/RK11 TECHTIPS > > > > RK8E HANDOUTS > > > > LP05 HANDOUTS > > > > 11/40 STUDENT HANDOUTS > > > > RX01 HANDOUTS > > > > PDP8E HANDOUTS > > > > PDP11 MAINFRAME TROUBLESHOOTING GUIDE INCLUDES FLOWS AND DECAIDS > > > > Thanks, Paul Anderson > > 217-586-5361

18 years, 5 months

Intertec Super Brain question

by ajp166＠bellatlantic.net

> >Subject: Re: Intertec Super Brain question > From: Fred Cisin <cisin at xenosoft.com> > Date: Fri, 07 Jul 2006 19:14:51 -0700 (PDT) > To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at classiccmp.org> > >On Fri, 7 Jul 2006, Chuck Guzis wrote: >> I've got a load of Super Brain CP/M diskettes and find that for whatever >> reason, the DAM (data address marks) seem to vary wildly on a disk-to-disk >> sample. >> What did the SB use for a diskette controller and why the varying DAM's >> (sometimes it's just a single sector or group of sectors on a track)? > >I've been told (but can't personally verify), that it's 179x 1791 (they use inverted data and everything If memory serves). Same as the 1793 only the data bus is inverted. They use the inversion to make their files less readable. They were, till everyone figured it out. >They sure screwed up that format, didn't they? > >The data is inverted relative to the address marks, >the index address mark is often too early for an NEC >(I often have to disable the index pulse to read them), >the head numbers on the second side are often wrong, >and I have no idea why the data address marks are flaky. >And they called DSDD 48tpi "quad" density, which meant >that when they came out with DSDD 96tpi, they called >that "Super Density", and abbreviated it "SD"! >(what is the next larger size of olives?) Classic case of the 179x could so they did. Didn't make it a good idea or even comforms to any standard. > >The good news is that it usually doesn't object to a properly >formatted diskette, so it's often possible to format a stack >of diskettes; use the SB to copy the files to them, and then >bring those diskettes back to read. > > >I tried to talk to Intertec about their formats. >At NCC '83, some of their suits told me that they could >not imagine ANY possible reason to convert data between >disk formats, other than to steal their "proprietary" >software (CP/M?), and that they would file a lawsuit if >I included any SB formats in XenoCopy! >That night was the first time that I ever added formats >to XenoCopy in a hotel room. >They never kept that promise. Yes there was the liklyhood that it meant more useful software would be available for the 'brain. Likely took them longer than a slow 8008 for that being a good thing to occur. >They used to have a sizable hobbyist following! Never seen that many though they were nice to use. Allison > >-- >Grumpy Ol' Fred cisin at xenosoft.com >

18 years, 5 months

OT: Replacing a drive belt on a Selectric II

by cclist＠sydex.com

I know this is pretty far OT, but it might help someone with an I/O Selectric too, so I'm posting it here. At any rate, I've got a very nice Selectric II typewriter with a broken drive belt. I've got a replacement, but I'm very wary about taking screwdrivers and whatnot to the mechanical marvel. Does anyone know how to do this who'd care to give me a step-by-step? I'd hate to throw the thing out--it is/was a great machine. Cheers, Chuck

18 years, 5 months

Intertec Super Brain question

by cclist＠sydex.com

I've got a load of Super Brain CP/M diskettes and find that for whatever reason, the DAM (data address marks) seem to vary wildly on a disk-to-disk sample. What did the SB use for a diskette controller and why the varying DAM's (sometimes it's just a single sector or group of sectors on a track)? Cheers, Chuck

18 years, 5 months

Intertec Superbrain

by aek＠bitsavers.org

It appears to use a 1791 Dave has schems at http://www.classiccmp.org/dunfield/supbrain/index.htm

18 years, 5 months

Fw: please forward if of interest: free Televideo luggable, Berkeley, CA

by jwest＠classiccmp.org

Someone wrote..... > There is an old Televideo luggable being given away for free in Berkeley, > California. It's at the street curb along with some other free junk in > front of 1213 Channing Way. Unfortunately, I don't know the model number > or operating condition, but it looked intact. It had evidently been kept > by some kind of hobbyist (judging from the other junk), although not > exactly a collector. Includes two built-in 5.25" floppy disk drives, if > that helps in the least. If someone is interested, contact me off-list immediately. Jay West

18 years, 5 months

Jumper settings for Camintonn Qbus memory?

by staylor＠mrynet.com

Anyone have jumper settings/documentation for Camintonn Qbus memory, particularly the CMV-1000? Can't find any references online. TIA, -scott

18 years, 5 months

Thurlby LA160 Logic analyser

by empiretheatre＠btconnect.com

Hi.. Do you still need a copy of the LA160 logic analyser software. I have just bought an LA160 on e-bay, and it came with it but on a 51/2" disk. You will need the upgrade EPROM's to go with it but I could copy these for you. I should be able to transfer it to a CD. Let me know.... Daniel.

18 years, 5 months

OMTI parallel port interface hack

by dgy＠DakotaCom.Net

Hi, I'm just finishing up some ideas on a quick-and-dirty parallel port (SPP)-to-OMTI interface (so Jules can salvage his "bits" :> ). Anyone like to add their two cents? Note the operative word here is "quick-and-dirty". If you want to build a monument to your own cleverness, you can design/build it yourself :> Goal here is something that can be built and debugged easily (so I'm NOT using an FPGA, microcontroller, etc.) If someone has access to a double sided PCB facility (to save the hassle of wire-wrapping the thing), I'll layout a 2 layer PCB (on the off chance that someone else might want to tinker with this stuff). Note that I am not aiming for performance. Just a way to coax bits off a disk drive so they can be imaged properly (is that correct, Jules?) Thanks! --don

18 years, 5 months

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test-drb July 2006