Ksarul

I have one from Japan that was accepted in Tokyo on 28 March. A few days later, they suspended all mail delivery to the US, and my package sat there until 24 May. It arrived in ISC Chicago on 26 May and hasn't moved since. . .and when I opened a case on it, the Post Office closed it without even trying to resolve the issue. My local postmaster told me Chicago has delays of a month or more for inbound mail right now, and outbound is just as bad or worse.

Here's a somewhat uncommon book, as the only way to get one BITD was to order it directly from Compute! Price is reasonable too. . .

I would say that the primary advantage would be that the IDE card is storing all of the data on the TI side of the interface. That is not a problem for most TIPI use cases, but it may make a difference.

That's a chip I hadn't looked for at Rochester yet. I have an account there, and that price is in the range I've had to pay for chips in the past from other (not always reliable) sources. I'll have to order some of them before my current batch runs out. . .I think I'm actually down below 50 again.

Something interesting I discovered in a recent auction. A seller had a PEB on sale with four TI cards in it--but one didn't have a label or the wires at the ends for card removal. The card was the disk controller--and when I opened the case up this morning, my suspicion was confirmed: the mystery card was a TI DSDD controller card. I haven't tested it yet, but it definitely a nice find nonetheless. That's the second one of these to show up in a PEB auction since the beginning of the year, so they are still out there. . .if you know what to look for. It turns out that the auction was doubly interesting. Turtles noticed that the speech synthesizer in the auction was one of the early ones with the speech module connector installed. . .so now I can tick one more item off of my list of missing things to look for.

I'm attaching the final version (along with the schematics) here. Hopefully that helps you and others building their own boards. HRD 4000B Construction Guide (Final-2).pdf A3-Horizon 4000B RAMDisk Schematics (Final-1).pdf

The silkscreen is correct--and there are three changed capacitors, not two. C-10 is also 10uF. I'm pretty sure I corrected that bit in the final version of the manual, but I will look again to be sure. Note, that C-10, C-17, and C-25 are ceramics, not tantalums. There are three 10uF tantalum caps on the board, but they are C-1, C-2, and C-3.

That configuration has never been tested--so I'm not sure if it will work. The only worries there are linked to the cable length--18 inches is about the maximum for an extension, and adding the three to four inches of traces on the splitter may be a bridge too far. It should have no issues when connected to a 12 inch extender cable though.

I haven't seen a printed case for it yet. I do have more of the boards on order now, so they will be back in stock soon.

A couple of thoughts here. There is a reason that there are seven cards connected to the flex cable card and the bus. The 74-series driver chips are designed to drive up to eight cards on the bus. The TI has logical provisions in place for up to 16 cards in total, but doing that assumes a split bus with two flex cable equivalents, each driving up to seven cards (eight if you make a 9-slot backplane or build the flex cable logic into the backplane). Go beyond this point carefully, as you may encounter all kinds of totally random errors on the bus that appear and disappear willy-nilly. One of the reasons I built my PEB Splitter cards was to allow two PEBs to be connected at the same time, as the flex cable card in each would never be driving more cards than the design limits, but you would still have a total of 14 available card slots if all of the cards in them were using different addresses. Several folks have run systems like this in the past, using the IEC splitter cable. That one sometimes ran into issues, introducing crazy errors due to the combined cable length (IEC+Flex Cable) being more than the 74LS244/245 bus drivers could safely handle. If the cables had been a few inches shorter, the problems would have been rare in the extreme (and limited to situations where the drivers wee weak already). My splitter avoided the length issue entirely by making the connection right beside the side port. You might also want to take a look into the newsletters from the TI Users Group in Brisbane, as they outlined a simple, 3-slot PEB substitute which could be easily extended (I think it was from one of the issues in the early nineties). The advantage there is that the alternative to the Flex Cable is already part of the design.

Actually, having the German manual to compare here would be a good thing, especially for those of us that speak both languages.

Just in case these come in useful to you. . .I think I've corrected any remaining errors in these, but if you find any, let me know and I'll update the Visio files and upload the corrected versions. A3-Nouspikel-IDE-HDC-P1.pdf A3-Nouspikel-IDE-HDC-P2.pdf

Actually, a variant of Myarc XB-II (v2.12) was released with the very first Geneves, as ABASIC wasn't ready yet. It was somewhat buggy, but I did write a few programs that used it. I may still have a copy of that on disk somewhere. I also had a friend at the time who had the 99/4A version of XB-2.12. We discovered that the two variants were just enough different that a lot of programs that worked in one failed in the other. It was seriously frustrating.

I think I've already removed all references to these software bits, but I will do another scrub to be sure. I checked the current manual. We made sure that the references to LHDROS, HDROS, CFG, and RAMDOS are identified as only useful for those still using really old versions of MDOS (1.23 or earlier). If you are using anything newer than that, they are to be avoided.

I've left mine off for weeks at a time and it holds the memory, but you can generally keep them that way for a few months. There is probably more drain from self-discharge than from current use by the HRD.

The various 80-column options all came out before the SAMS (then titles the AEMS) was available, and it was pretty much the first general-purpose expansion to come out that gave the user access to seriously expanded memory. The Myarc card with its 128K OS came out earlier, but it really wasn't a general purpose expansion, it was only an expansion that could be tweaked to work as one. About the only application that ever took advantage of that tweaking capability was Myarc Extended BASIC II. By the time SAMS was on the street, most of the programs that took advantage of 80-columns were already written. SAMS really didn't reach a critical mass of community penetration until many years later--so software supporting it was slow in coming. That isn't the case anymore, as a lot of new software looks for it and knows what to do with it when it finds it.

Actually, I am pretty sure I have a copy of the manual. I'll have a hunt to see if I can dig it up this weekend. . .

Just waiting for my Pi-0 to get here. . .

The best prices I've seen on the Dallas chips is in the $21 to $26 range. The 512K chip pinout is identical to the normal 512K SRAM chips, so yes, they should work on the 1M board too. One note on chips coming from China here: about 75% of the chips they are selling do NOT have the original top surface or labeling. This could be because they opened them up to put new batteries inside, but this could also just be an attempt to put a newer date code on them. Most of them should work as a standard SRAM though, which is really all I cared about when I bought mine, as these are just about the only 2M chips still available that use 5V and come in DIP format.

Ich muß den jetzt für den 4000B erweitern. . .

@Schmitzi, I had issues with the picture too--it downloaded, but it would not open in a picture viewer afterward. I tried opening it with Paint--and it opened. It would not save a usable picture in JPG or PNG format, but it did save fine as a bitmap. I then saved the bitmap as a JPG or as a PNG, and those worked flawlessly. There must have been a malformed bit somewhere in the original picture that the process I followed cleared. . .

The next group of eight boards is at about 90% complete on the soldering work, which is perfect timing, as my next batch of NiCd batteries arrived today--and I needed them to finish building this group of boards. . .

I believe there is a development kit out there that allows folks to write their own code to use it (I'm not sure who wrote the tools, Rob Patton?). So it is some hardware that can use some more love. . .

Note that the bag the MBX is in is pink poly--that will distort the beige color to make it appear to be yellow. The cabling is the tell on this one though: the microphone cabling is mostly in the original looped shape that it would have been shipped in, but it is missing the tie and the bag is otherwise jumbled out of the original shape. The power supply cable is even further from the state it would have been shipped in. That said, there is no serious damage to the microphone foam, so it definitely never saw much in the way of use.

Every reference for the BQ4847 I've seen refers you back to the BQ4845 datasheet for the detailed functional description. The BQ4847 datasheet only gives a general description and shows the things that are different. bq4845 RTC Datasheet.pdf