This issue came up years ago and IIRC the manuals are correct and no one needs to be 'reamed'. Apparently there were two standards for IDE headers, one with pin 1 on the top row and the other on the bottom; as with some other 'standards' it looks like the Japanese started with one standard and the rest of the world went with the other. The effect was that the even pins became the odd wires etc., i.e. pin 1 on the computer became the second wire in the cable.
I think the original Tandy cables used connectors that matched the computer/manual but when I tried to find some more to make some DVI cables they had apparently become unobtainium. At least that's what I remember; I'm not at home so I can't check but if anyone has an original cable, compare the markings and signals with a 'standard' connector. Not to be confused with the other issue, that plugging a male connector into a female (or is it a male...) also effectively swaps the pins. On Tue, Nov 19, 2024 at 5:42 AM Brian K. White <[email protected]> wrote: > There was another thread about the same problem recently: > > http://lists.bitchin100.com/private.cgi/m100-bitchin100.com/2024-September/090053.html > > With a cable that looked like this: > > http://lists.bitchin100.com/private.cgi/m100-bitchin100.com/attachments/20240925/4ad2aa75/attachment.jpg > > See my 2 follow up responses in that thread. > > You do need one twist in the wires on 102/200, but visually it's no twist. > top-to-top as you say. > But when you put two of the same gender connector back to back, that > actually produces a twist, because pin 1 of one connector can only match up > with either pin 2 or pin 39 of the other connector. > > The cable in the pic then adds another twist with those short wires. > Double twist == no twist. Pin 1 is now going to pin 1, which is wrong. > > To make it all extra excellent chefs kiss confusing... the T102 and T200 > manuals label the pin numbers WRONG. > > Pin 37 vs 38 is an easy way to tell what's *really* going on because that > one has RAMRST on pin 38 and NC on 37. and RAMRST is basic almost like > power. It's at 5v the entire time the machine is turned off but has > batteries, or at least 3v if relying on the internal memory battery. So > it's easy to check with a simple dmm. > > The manuals say RAMRST is on 37 but it's really on 38. All pins are > actually swapped even for odd. It's just a numbering/labelling thing in > both the 102 and 200 manuals, and in all forms of the manuals, user guide, > service manual, tech ref. It's not related to how the pins need to be > twisted from the DVI to the 102/200. If the pins were labelled correctly in > the manuals, then pin1 from the dv needs to go to pin 2 on the computer. > Maybe that's why they labelled them wrong is so the numbers would match the > dvi, without actually changing the physical pinout to actually match the > dvi?? > > The good news is, the power pins are all doubled and symmetrical. Both > pins 1 and 2 have VCC, and both pins 3 and 4 have GND, so flipping 1/2 3/4 > wrong won't hurt anything. Similarly,, both pins 39 and 40 are NC, so if > you flipped the connector over that way and put VCC into 39 & 40, no > problem. But it also means you can't use the power pins to tell if you have > it wired up correctly. > > RAMRST could possibly be hurt, or hurt something, if you had a worse error > than you actually have. RAMRST is actually a power pin when the machine is > off, keeping external ram powered and disabled (active-low chip-enable). So > it's possible to hurt that if shorted to gnd, but just doubling (aka > cancelling) the twist won't hurt because the other pin is NC, so you'd just > be connecting RAMRST to NC. No problem. But if you flipped it on the other > axis so 1 & 2 went to 39 & 40, that would put RAMRST pin 38 on either 2 or > 4, GND. But I don't think you could do that since the connectors have > polarity notches. The only error is in those incorrect extra twist wires, > which are only crossing the odds & evens, not end for end. > > Whoever numbered the pins in the 102 & 200 manuals... I hope they were > just an intern and got reamed and never did that again... > > -- > bkw > > On 11/18/24 23:54, Michael Brutman wrote: > > I know this is going to sound crazy but ... > > On the M102 system bus connector Pin 1 is marked on the top side of the > connector next to the reset button. That means pin 37 should also be on > the top row - second pin on the top row of the other side near the printer > port. > > If I probe a machine with a logic analyzer and press reset, pin 37 (RAM > RESET) does nothing. It's neither negative or positive. It is just dead. > But if I probe what appears to be pin 37, I get the expected behavior on > the reset button - logic low that then goes high while the button is being > held. > > The same thing is happening on pin 32 (RESET). If Pin 1 is marked > correctly then pin 32 should be on the bottom row, That pin is active and > constantly changing state, so it's clearly not reset. But pin 33 (INT REQ) > would have that behavior. Moving to what should be pin 31 (top row) shows > logic low normally and logic high when I hold the reset button. > > Is the IO Bus on my machine wired with the pins already reversed? > > > > > > On Mon, Nov 18, 2024 at 7:22 PM Jerry Davis <[email protected]> wrote: > >> Seems to be a cable/connector issue. >> >> I repeated the sequence you described on the M100 and DVI that I have >> here and BASIC loads and starts as expected. >> >> I have a ribbon cable with a broken signal pin at the M100 end and my >> M100 does what yours does when I use that cable. Which makes me think you >> may have a cable problem. >> >> Jerry >> >> On Mon, Nov 18, 2024, 7:20 PM Michael Brutman <[email protected]> >> wrote: >> >>> I powered on the M102 first, then the DVI. After the copyright message >>> came up I tried the reset button, power off and then power on, and a cold >>> start. The machine restarted but the amount of free memory remained the >>> same and the DVI disk light did not turn on. I'm fairly certain the DVI is >>> not seeing the reset signal from the M102. >>> >>> Going to BASIC and using SCREEN 1,1 fails because I'm still on the >>> built-in BASIC at this point, as DISK BASIC never got moved into the memory >>> on the M102. >>> >>> >>> -Mike >>> >>> >>> On Mon, Nov 18, 2024 at 3:20 PM Jerry Davis <[email protected]> wrote: >>> >>>> After executing the power-on sequence and getting the "Microsoft" >>>> message, did you execute the BASIC command "SCREEN 1,1" from the Model 102? >>>> >>>> The above command switches output to the CRT on the DVI and displays >>>> the key labels at the bottom of the CRT. >>>> >>>> Jerry >>>> >>>> >>>> >>>> On Mon, Nov 18, 2024 at 11:39 AM Michael Brutman <[email protected]> >>>> wrote: >>>> >>>>> I've tried all three methods - power off/power on, Reset, and cold >>>>> start. There is no difference. Also, the two machines have no options or >>>>> expansions that would alter their behavior. >>>>> >>>>> The technical service manual has a reasonable troubleshooting guide >>>>> which gives specific pins and behaviors to look at. I'd still like to >>>>> find >>>>> a known good cable before breaking out an oscilloscope, but at least the >>>>> schematics and behaviors are documented. >>>>> >>>>> The length of the cable is kind of freaking me out a little bit - for >>>>> a bus that's a long stretch. Do you know the length of the original >>>>> factory cable? >>>>> >>>>> >>>>> -Mike >>>>> >>>>> >>>>> On Mon, Nov 18, 2024 at 9:19 AM Royce Taft <[email protected]> >>>>> wrote: >>>>> >>>>>> One other thing you could try is a cold start (CTRL+PAUSE+RESET). It >>>>>> will wipe all your 102’s memory, but maybe it will help? >>>>>> >>>>>> Royce >>>>>> >>>>>> Sent from my iPhone >>>>>> >>>>>> On Nov 18, 2024, at 08:34, Michael Brutman <[email protected]> >>>>>> wrote: >>>>>> >>>>>> >>>>>> I had checked the connectors and pins before I wrote, and I was even >>>>>> going to check for continuity on each pin but that's going to take a >>>>>> while >>>>>> and be error prone with 40 pins. The connector on the underside of the >>>>>> DVI >>>>>> has the snap-in latches which are engaging. I can't push any further >>>>>> and I >>>>>> haven't bent any pins. The cable is new from Gregory (Arcade Shopper), >>>>>> so >>>>>> I don't have a lot of reason to suspect it. >>>>>> >>>>>> Besides trying two different 102s I've also tried batteries and wall >>>>>> power for the 102s, and I even upgraded one to max out the RAM just in >>>>>> case >>>>>> I was missing a memory requirement. >>>>>> >>>>>> The DVI unit itself was pristine on the inside when I first looked at >>>>>> it. I'll have another peek inside to check the connector; perhaps it >>>>>> experienced some trauma and there are broken traces on it. But I really >>>>>> don't want to look for problems where they are unlikely or fix things >>>>>> that >>>>>> are not broken .. I've learned that every time I disturb something there >>>>>> is risk involved. >>>>>> >>>>>> Is there anybody in the Seattle area (northern suburbs) with a known >>>>>> good cable? If I can eliminate the cable as a possibility then there is >>>>>> only the DVI connector, as the rest of it seems to function normally. >>>>>> >>>>>> >>>>>> -Mike >>>>>> >>>>>> >>>>>> On Mon, Nov 18, 2024 at 7:10 AM Royce Taft <[email protected]> >>>>>> wrote: >>>>>> >>>>>>> When I had this issue, it turns out I hadn’t snapped the connector >>>>>>> in fully on the underside of my M100. I would disconnect it and ensure >>>>>>> no >>>>>>> pins became bent and flattened out. If the pins look good, carefully >>>>>>> replace the connector and snap it firmly into place. >>>>>>> >>>>>>> When making my cable, to figure out the location of pin 1 on the >>>>>>> M100 and the DVI, I think I used a multimeter and the pin outs in the >>>>>>> various manuals to look for ground pins which gave some insight into the >>>>>>> orientation of the connectors. >>>>>>> >>>>>>> Seeing “please wait” followed by a Microsoft copyright is a very >>>>>>> good sign that your boot disk was successfully read. >>>>>>> >>>>>>> Royce >>>>>>> >>>>>>> Sent from my iPhone >>>>>>> >>>>>>> > On Nov 17, 2024, at 21:20, Michael Brutman <[email protected]> >>>>>>> wrote: >>>>>>> > >>>>>>> > >>>>>>> > Ok, here is the part I hate ... getting things put together and >>>>>>> then not having it work. >>>>>>> > >>>>>>> > I'm using Greg's cable kit with a Tandy 102. I have the twist >>>>>>> adapter on the 102 side, red stripe oriented as in the pictures on the >>>>>>> Wiki. (The red stripe closer to the 'S' of "System bus".) That goes >>>>>>> into >>>>>>> the IDE ribbon cable, which is connected to the DVI also using the >>>>>>> orientation in the pictures from the Wiki. >>>>>>> > >>>>>>> > I used Teledisk to create the disk image. I powered on the 102 >>>>>>> first, as per the DVI user manual. When I power on the DVI I get the >>>>>>> "Please wait!" message, and then I get the Microsoft copyright message. >>>>>>> All of this is good so far. >>>>>>> > >>>>>>> > Where things fail is when I try to load disk BASIC onto the 102. >>>>>>> The instructions say to use the Reset button or to power the machine on >>>>>>> and >>>>>>> off. Neither has any effect, and I've tried it with two different 102s. >>>>>>> > >>>>>>> > What am I missing here? >>>>>>> > >>>>>>> >>>>>> >
