smp Posted February 11 Share Posted February 11 (edited) Good day! I recently purchased a TM 990/100MA board on eBay for what I thought was a good price. I knew that the 9900 and 9901 were missing, but I have another source. What I was surprised with is that U23 is also missing, and I found that U23 is a 32x8 PROM! I have not found what the code is for this PROM. Can anyone help me? Is there a source for the 74s288 with the correct code programmed in? Is there any source for the code to possibly program a new PROM? I would greatly appreciate any advice and assistance that you may be able to provide! smp These images show what the board is supposed to look like, and what my board looks like: Edited February 11 by smp Added second image of my board. Quote Link to comment Share on other sites More sharing options...
Stuart Posted February 11 Share Posted February 11 I can get the data for the PROM ... but does anyone in the US have a programmer that will handle an old 74S288 or compatible 32x8 bipolar PROM? Quote Link to comment Share on other sites More sharing options...
+FarmerPotato Posted February 12 Share Posted February 12 To program a 288 nowadays, I think you'd have to make a programmer from a Arduino or such. The programming voltage is 10V with 100 microsecond pulses. (data sheet) Alternately, it would be possible to adapt a more recent PLD to do the job. The cheap TL866II or XGPro T56 will program small PLDs like ATF16V8B, which is in stock at DigiKey for $1.23. You'd need a tiny circuit board adapter. Not a big deal. The available PLDs aren't close to the 288 pinout. The inputs and outputs are flipped! 1 Quote Link to comment Share on other sites More sharing options...
+Ksarul Posted February 12 Share Posted February 12 I just checked all eight of my programmer's device lists to see if any of them would program a 74S288--none of them do. . .which probably leads back to @FarmerPotato's suggestion as the easiest solution to the problem once you have the necessary data file from a 288. 1 Quote Link to comment Share on other sites More sharing options...
humeur Posted February 12 Share Posted February 12 (edited) 9 hours ago, Stuart said: I can get the data for the PROM ... but does anyone in the US have a programmer that will handle an old 74S288 or compatible 32x8 bipolar PROM? I have what it takes for programming lots of old components. I also have nine equivalents to 74ls288 27s19, but I'm not at US JL Edited February 12 by humeur 2 Quote Link to comment Share on other sites More sharing options...
smp Posted February 12 Author Share Posted February 12 Thanks very much for responding to my request! The first question i have is whether or not you think it’s good to put money and effort into this particular board? Since the high value chips were taken from this board, do you think they were stripped before tossing it out, or do you think that the board failed and they were harvested? Are these TI boards robust? Do I have a good chance of bringing it back to life? The Seller has offered this other board to me for the same price ($200): TEXAS INSTRUMENTS PCB CIRCUIT BOARD TM990/101MA 994728/994726/994725-1 I might be able to get them down lower. Could you please take a good look at the pictures and tell me if you think it might be worth it? I see a bunch of blue wire patches - what do you think about those? Please let me know if you think I should stop going in this direction and if there are other options. I’d like to get a TI SBC up and running with TI-Bug, and I would be interested in a 4-slot backplane and a 64K RAM memory board to go along with it. Then I’d like to get some files like Assembler, BASIC and FORTH that I could load in via the terminal connection. As well, once one of those programs are in, I could also put in my programs to play with via the terminal connection. Oh, another question is, what do you recommend as a power supply? Thanks a million for listening and trying to assist! smp Quote Link to comment Share on other sites More sharing options...
+FarmerPotato Posted February 13 Share Posted February 13 @smp Yes, the 990/101MA board will be much better. (I recently got one, too.) My understanding is TIBUG was in its first EPROM bank, whereas the 100 did not have it. That board is missing the 9900 and 9901 (U1). Both easy to buy new or used. The EPROM stickers match the socket# label. They go in pairs: 42+44, 43+45 and can be 1K or 2K size. (Max 8K ROM.) The 101MA has a 74S287 PROM 256x4. The function of the PROM is to decode address lines A0:4 which gives 2K blocks. (the other 3 address bits are jumper selects.) Its outputs are chip enable signals to the right EPROM or RAM. There are 2 EPROM banks (1 bit each) one RAM bank and one bit indicating on-board/off-board memory. I've got an ancient EPROM programmer for 2716s (last used on Windows 7.) 2 Quote Link to comment Share on other sites More sharing options...
Stuart Posted February 13 Share Posted February 13 (edited) On 2/11/2023 at 10:51 PM, Stuart said: I can get the data for the PROM ... but does anyone in the US have a programmer that will handle an old 74S288 or compatible 32x8 bipolar PROM? Thanks for the replies, folks. Someone pointed me to www.hobbyroms.com which seems to provide exactly the service needed. Edited February 13 by Stuart 3 Quote Link to comment Share on other sites More sharing options...
+Ksarul Posted February 14 Share Posted February 14 Using the cross-reference list, I discovered that my Advin U84P will program one of the substitute chips for the 74S288: the AMD 27S19, so there is at least one of us here that can help with getting this file onto silicon. 2 Quote Link to comment Share on other sites More sharing options...
+FarmerPotato Posted February 14 Share Posted February 14 2 hours ago, Ksarul said: Using the cross-reference list, I discovered that my Advin U84P will program one of the substitute chips for the 74S288: the AMD 27S19, so there is at least one of us here that can help with getting this file onto silicon. PROMs are made from Tungsten-Tantalum fuses. You have to tantalize the bits. 1 1 Quote Link to comment Share on other sites More sharing options...
smp Posted February 14 Author Share Posted February 14 (edited) Thanks very much, folks, for all your advice and assistance here! I just purchased this TM 990/101MA over the weekend: https://www.ebay.com/itm/223719583628 This board seems to be more complete, missing only the serial chip for the second SIO port. I am more confident that this board may be functional. So, the pressure is off a bit for making the PROM for my TM 990/100MA. I can contact Stefan at Hobbyroms, and purchase that missing PROM, and also get TIBUG burned into a couple of 2708s for the TM 990/100MA, while I work with my (hopefully better) TM 990/101MA. I also ordered this Mean Well triple power supply from Jameco: https://www.jameco.com/z/RT-85B-MEAN-WELL-88W-Triple-Output-Switching-Power-Supply_323652.html And also this spare chips package on eBay: https://www.ebay.com/itm/113467270983 I am quite excited now, waiting for all these packages to arrive! Thanks again for all your help! smp Edited February 14 by smp added another purchase link 1 Quote Link to comment Share on other sites More sharing options...
jbdigriz Posted February 14 Share Posted February 14 (edited) Sorry, late to the party here (VPS failed over the weekend - panic city), but I'm archiving this thread. Very useful info. Please keep us posted, Stephen. Looks like there've been some bargains on TM990 stuff lately. Maybe enough for enthusiasts and tinkerers to assemble systems affordably. Edited February 14 by jbdigriz 2 Quote Link to comment Share on other sites More sharing options...
smp Posted February 15 Author Share Posted February 15 I received my TM 990/101MA today! Here's a photo of how it was received: I think it looks in excellent shape. I've now recorded all the jumper positions - all correct for EIA/RS232/Terminal and 2716 EPROMS - and I've set up my one saved 100 pin connector with power jumpers. Now I wait for my power supply to arrive... Getting more excited now! smp 4 Quote Link to comment Share on other sites More sharing options...
smp Posted February 16 Author Share Posted February 16 A small update this morning: I had one S-100 connector in my spare parts collection, and I found that it fits the TM 990 card edge connector perfectly. I have it wired for the power connections, so when my power supply arrives, I will be ready to go with testing. Then, I had a brainstorm: Gary Kaufman has a bunch of S-100 replica boards available for sale here: http://the-planet.org Included in that selection is a 4-slot backplane, originally used in the Altair 8800, and uses the same 100 pin 0.125" spacing connectors. This 4-slot backplane will be ideal for a small TM 990 system like I want to build up! The power supply busses for the TM 990 will have to be beefed up, but that should not be a problem when soldering in the connectors. Just so that everyone knows (whether or not this is news to anyone) Gary has both the thin and thick versions of the PCB available. He also has the proper connectors available, or you can source them yourself. Thanks for listening! smp 2 Quote Link to comment Share on other sites More sharing options...
smp Posted February 16 Author Share Posted February 16 I attached my power supply and a serial connection late this afternoon, but I did not get any response on my Mac pretending to be a terminal. I had hoped that the 2716s on board had the TIBUG and the Line By Line Assembler in them, but assuming the board is working, the EPROMs probably have some other program in them. Now I'guess I'll definitely have to get going with some 2708s with TIBUG burned into them. One step at a time, I suppose. smp Quote Link to comment Share on other sites More sharing options...
Stuart Posted February 16 Share Posted February 16 6 hours ago, smp said: A small update this morning: I had one S-100 connector in my spare parts collection, and I found that it fits the TM 990 card edge connector perfectly. I have it wired for the power connections, so when my power supply arrives, I will be ready to go with testing. Then, I had a brainstorm: Gary Kaufman has a bunch of S-100 replica boards available for sale here: http://the-planet.org Included in that selection is a 4-slot backplane, originally used in the Altair 8800, and uses the same 100 pin 0.125" spacing connectors. This 4-slot backplane will be ideal for a small TM 990 system like I want to build up! The power supply busses for the TM 990 will have to be beefed up, but that should not be a problem when soldering in the connectors. Just so that everyone knows (whether or not this is news to anyone) Gary has both the thin and thick versions of the PCB available. He also has the proper connectors available, or you can source them yourself. Thanks for listening! smp The TM990 backplane has some termination resistors on some of the signals that the Altair board does not. Not sure whether their absence would stop it working or whether they help near edge case conditions. 1 Quote Link to comment Share on other sites More sharing options...
smp Posted February 17 Author Share Posted February 17 Thanks for that reminder, Stuart. Looks like I have a bit more to think about if I go this route. smp Quote Link to comment Share on other sites More sharing options...
+FarmerPotato Posted February 17 Share Posted February 17 (edited) On 2/16/2023 at 4:51 PM, Stuart said: The TM990 backplane has some termination resistors on some of the signals that the Altair board does not. Not sure whether their absence would stop it working or whether they help near edge case conditions. Can't hurt to put in just the termination that TI has in their 4-slot. Just 3 signals I think? And pull-ups for RESTART.B and the like. Termination is not necessary for signal integrity on short traces. And 3 MHz is low speed. Should not matter at all, when you have only one card. Another thing, maybe not all traces go straight through. (Still those don't matter for just one card.) There may be lines that require jumpers at each slot. The 12-slot has resistors on many more traces. The trace length and the sockets each add more capacitance, making terminators necessary. From memory, I'll check sources later The Altair has 220 + 330 terminating resistor networks, in abundance. Anecdotally: these were the cheapest IC resistor networks in 1975. I looked at the Altair today. There are no terminating resistors. The S-100 bus has sockets in the center, so the card guides are wrong for the TM990, but that doesn't matter. I noticed a TMS8080A with date code 7819! TI uses slightly different values, but the idea is to terminate into the middle tap, to get 3V or anywhere above a TTL V_h_min, which is 2.0V--preferably 2.4. Edited February 18 by FarmerPotato Strike Quote Link to comment Share on other sites More sharing options...
smp Posted February 17 Author Share Posted February 17 (edited) Yesterday evening, I finally received the original TM 990/100MA board I purchased on eBay. Even though the photo the Seller provided showed that the 74S288 was missing, the board I received has it installed. So, the main reason that I started this topic has become a non-issue. I sent a Message to Stuart, telling him about this so that he will not expend any more effort trying to get the code for me or to find a substitute chip. Now, I'll send off my message to Stefan at Hobbyroms requesting two 2716s with TIBUG, and two 2716s with the LBLA. WHEW! smp Edited February 17 by smp typo... 2 Quote Link to comment Share on other sites More sharing options...
+FarmerPotato Posted February 17 Share Posted February 17 @smp I'm glad you started this thread! I learned a lot from your questions. I did not realize that the S-100 backplane is a match! Quote Link to comment Share on other sites More sharing options...
smp Posted February 17 Author Share Posted February 17 (edited) @FarmerPotato No problem at all! I am usually full of questions and having never been down this road with TI 990 SBC systems, I'm certain that I'll come up with more. Here's a photo of my latest board: To me, it looks to be in excellent shape. My package of spare parts is still on the way, and I've sent a message off to Hobbyroms -> EPROM PRO (http://www.eprompro.com/computers.html) requesting 2716s with TIBUG and LBLA burned in. In the end, I may end up with two working SBCs, but it will be a while before I will be able to know. Hopefully, at least one of the SBCs will come to life without too many problems! Thanks for listening! smp Edited February 17 by smp added URL for EPROM PRO... 1 Quote Link to comment Share on other sites More sharing options...
+retroclouds Posted February 17 Share Posted February 17 1 hour ago, FarmerPotato said: @smp I'm glad you started this thread! I learned a lot from your questions. I did not realize that the S-100 backplane is a match! You guys should do a couple of youtube videos on the stuff you're doing with the 990. I mean, that is fascinating stuff and there's not much on the 990 to be found on Youtube if at all. Doesn't have to be anything fancy, but would love to see what you're tinkering with and come to see the system alive 🙂 4 Quote Link to comment Share on other sites More sharing options...
jbdigriz Posted February 18 Share Posted February 18 (edited) I hear there are downsides to being a Youtube star. I follow some of the car guys (and gals) and I'm not quite sure how they cope with some of the craziness that results. Regardless, I find a good web site far more useful than wading through videos. Stuart's pages in particular are an amazing resource for anyone getting into the TM990 and other non-4A systems. Your point is taken, though. Edited February 18 by jbdigriz 4 Quote Link to comment Share on other sites More sharing options...
smp Posted February 18 Author Share Posted February 18 (edited) I heard back from Stephan at Hobbyroms / EPROM PRO this morning, and he will be burning the four 2716s for me. Two with TIBUG and two with the LBLA. Since they will be coming to me from Canada, I probably have a 10 day wait now. All this waiting! Hopefully the payoff will be great. smp Edited February 18 by smp typo... Quote Link to comment Share on other sites More sharing options...
smp Posted February 18 Author Share Posted February 18 (edited) OK, here is my latest question for you smart folks. I started looking at the TIBUG listing I have: http://www.bitsavers.org/components/ti/TMS9900/tm990-100/MP324_990-401_TIBUGlst.pdf And, of course, I'm confused. There are a bunch of notes on the listing, and thank goodness for that. I know that TIBUG fits into two 2708 EPROMs that start at the bottom of memory and go from $0000 to $03FF. I wanted to check out the files I got from Stuart's site and sent off to have burned into EPROMs: http://www.stuartconner.me.uk/tm990/eprom_images/tibug-u42-u44.zip http://www.stuartconner.me.uk/tm990/eprom_images/lbla-u43-u45.zip That is what got me into my latest confusion! When I look at the listing, there is a note saying that the entry point of $0080 in the listing is actually $0040. After getting myself all confused because my binary file viewer shows the addresses of the bytes in the file as decimal numbers, and the listing shows the addresses of the bytes in hexadecimal, I finally was able to match up the bytes at the entry point in the two files with the listing, and indeed, they show up in the files starting at $0040, not $0080 as the listing says. This is my first time with a 16 bit machine that has its program stored in two parallel EPROMs. Am I confusing myself here? I am about to get two 2716 EPROMs with the TIBUG data burned in at $0000-$03FF in each of them, and another two 2716 EPROMs with the LBLA data burned in at $0000-$03FF in each of them. Will I be OK? Will these EPROMs work in either of my SBCs (both of them are jumpered to accept 2716s)? Please help me to understand this if you can. If anyone has either a TM 990/100MA board or a TM 990/101MA board with TIBUG burned into 2716s. please speak up and let me know. smp Edited February 18 by smp typos... Quote Link to comment Share on other sites More sharing options...
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