Level42 Posted October 22, 2017 Share Posted October 22, 2017 So, I've been working on some 130XE boards recently and my friend Fred sent me a picture of his 130XE. And it seems there's something weird going on......... See the pictures.....three different 130XE boards.... On the last one it's hard to see, but ALL RAMs are Samsung -20 type, but the top left is a Matsushita Panasonic -15 type. The other two are all mT's (one with -20 only, the other a mixed bag of -15 and -20), but again....the top left ones ar different, both NEC and -15. It's almost like they did this with a goal......but what ?? It's just one bit of the entire range of 8 so there doesn't seem to be a logical reason.....maybe they did some preliminary test on one bit of the "first" RAM during production ? Anyway.....I wonder, what do other people have in their 130XE's ? Please have a look and post a picture Quote Link to comment Share on other sites More sharing options...
hunter44102 Posted October 22, 2017 Share Posted October 22, 2017 that's interesting. will check mine, never noticed that 1 Quote Link to comment Share on other sites More sharing options...
NISMOPC Posted October 22, 2017 Share Posted October 22, 2017 The NTSC 130XE's & 65XE's I've had in my possession were all mT branded. That's been about 10 all together. If you have one or two random chip's in there, it's more then likely it was replaced at the factory during final assembly testing and a faulty chip was identified OR previous owner replaced a faulty chip. Quote Link to comment Share on other sites More sharing options...
erichenneke Posted October 22, 2017 Share Posted October 22, 2017 I've wondered about this before too. I have had at least 3 ntsc 130xe's that have had this "different" top/left ram chip vs. the others, like you are describing here. 1 Quote Link to comment Share on other sites More sharing options...
Level42 Posted October 22, 2017 Author Share Posted October 22, 2017 (edited) I've wondered about this before too. I have had at least 3 ntsc 130xe's that have had this "different" top/left ram chip vs. the others, like you are describing here.AHA !!! We're onto something !! Nismopc: have a good look at the pictures...do you see any hand solderings ? And wouldn't any smart repair guy throw in a socket ? No, all three are factory original like this, and only wave soldered..... And also.....always the top left one isn't random... Edited October 22, 2017 by Level42 Quote Link to comment Share on other sites More sharing options...
NISMOPC Posted October 23, 2017 Share Posted October 23, 2017 AHA !!! We're onto something !! Nismopc: have a good look at the pictures...do you see any hand solderings ? I stand corrected. Here is one of the 130XE's I purchased with a bad keyboard membrane. Random chip upper left corner... 1 Quote Link to comment Share on other sites More sharing options...
toddtmw Posted October 23, 2017 Share Posted October 23, 2017 Well, mine was upgraded to 320, so not sure this will help, but this is what it has. 1 Quote Link to comment Share on other sites More sharing options...
+DrVenkman Posted October 23, 2017 Share Posted October 23, 2017 My only 130XE has all 15 Micron DRAMS and one NEC, right up in that upper left corner. Dubya. Tee. Eff. 1 Quote Link to comment Share on other sites More sharing options...
RodLightning Posted October 23, 2017 Share Posted October 23, 2017 (edited) I've wondered about this before too. I have had at least 3 ntsc 130xe's that have had this "different" top/left ram chip vs. the others, like you are describing here. Add my 130XE to that list with one NEC dram in the top left position. I'm starting to think it was a deliberate act at manufacture. Edit: All the other drams on it are the notorious MT Micron Technology. Edited October 23, 2017 by RodLightning 1 Quote Link to comment Share on other sites More sharing options...
erichenneke Posted October 23, 2017 Share Posted October 23, 2017 Do a google search on "130XE motherboard" images. It looks like almost every example has this characteristic. 1 Quote Link to comment Share on other sites More sharing options...
Level42 Posted October 23, 2017 Author Share Posted October 23, 2017 Well, mine was upgraded to 320, so not sure this will help, but this is what it has. IMG_1556.JPG Thanks for posting, but we can't see the original RAMs under those.....but no worries..... Already have SO many confirmations. I think it's fair to conclude that A) both PAL and NTSC machines have this "feature" (which makes sense as the RAM has nothing to do with NTSC/PAL) B) this is a structural, deliberate production choice. But WHY ?? I really can't think of anything except for that maybe they had some factory test procedure that only checked out the "first" RAM chip ? But that would be kind of crazy as all the chips on the board were placed (and soldered) in one go. Knowing Tramiel Atari, they would do ANYTHING to save a single,cent in production costs, so there MUST be a reason why they put a slightly more expensive RAM chip in that top-left spot..... Maybe something to do with the MMU ? Or FREDDY ? Are there any Tramiel era 800XLs out there with mT RAMs that also have a good brand as the one on the top position ? Quote Link to comment Share on other sites More sharing options...
Level42 Posted October 23, 2017 Author Share Posted October 23, 2017 Do a google search on "130XE motherboard" images. It looks like almost every example has this characteristic.Excellent idea....why didn't I think of that....I actually googled for pics of the various system motherboards lately.....Yes you are right I also repeated the google with 130XE PCB....about the same results. I think we can add a conclusion: C) They ONLY did this if the rest of the RAMs were mT brand. Found a few pics with different brand RAMs and if so they were ALL the same brand. Interestingly, I found one with all -20 versions, but again ....not mT's. Quote Link to comment Share on other sites More sharing options...
+kheller2 Posted October 23, 2017 Share Posted October 23, 2017 Excellent idea....why didn't I think of that....I actually googled for pics of the various system motherboards lately..... Yes you are right I also repeated the google with 130XE PCB....about the same results. I think we can add a conclusion: C) They ONLY did this if the rest of the RAMs were mT brand. Found a few pics with different brand RAMs and if so they were ALL the same brand. Interestingly, I found one with all -20 versions, but again ....not mT's. Didn't your original post disprove that conclusion? "On the last one it's hard to see, but ALL RAMs are Samsung -20 type, but the top left is a Matsushita Panasonic -15 type." 1 Quote Link to comment Share on other sites More sharing options...
towmater Posted October 24, 2017 Share Posted October 24, 2017 Well you have me curious, so I took a look. One Fairchild in the upper left, the rest are MT. But what's with all of the unused solder pads towards the front? PAL stuff? 1 Quote Link to comment Share on other sites More sharing options...
JamesD Posted October 24, 2017 Share Posted October 24, 2017 Maybe there is some timing that doesn't work right on some RAM chips and the single chip was the fix 1 Quote Link to comment Share on other sites More sharing options...
Level42 Posted October 24, 2017 Author Share Posted October 24, 2017 (edited) Well you have me curious, so I took a look. One Fairchild in the upper left, the rest are MT. But what's with all of the unused solder pads towards the front? PAL stuff? Ha, yet another one You mean next to the small metal case on the right of it ? Those parts are all inside that little metal,case. The board provides two possibilities: loose crystal and the required components to "drive" it, or that little metal case which contains the crystal and everything to drive it inside....I have seen the metal clock generator mostl, only last Saturday I saw an XE with loose crystal and parts. Edited October 24, 2017 by Level42 Quote Link to comment Share on other sites More sharing options...
towmater Posted October 25, 2017 Share Posted October 25, 2017 If you look at Toddtmw's post above you'll see u21 and a bunch of other unpopulated stuff. Quote Link to comment Share on other sites More sharing options...
Level42 Posted October 25, 2017 Author Share Posted October 25, 2017 Well, mine was upgraded to 320, so not sure this will help, but this is what it has. IMG_1556.JPG Yes there are two "areas" of unpopulated stuff. On this picture: the stuff on the far lower right is what I meant. This is the main system clock generator (area). The other area, also on the right, more on the top: Y2 the position for the second crystal which is required for PAL systems and hence lacks on NTSC boards. The parts around it are are for supporting this crystal (getting it to oscillate and produce a decent clock wave signal). Quote Link to comment Share on other sites More sharing options...
Level42 Posted October 25, 2017 Author Share Posted October 25, 2017 (edited) Maybe there is some timing that doesn't work right on some RAM chips and the single chip was the fixNot a bad suggestion.....weird but not impossible...guess we'd have to know at the lowest level how RAM is addressed and data fetched/written...normally I would say all data bits are read/written "at once" but maybe.....not so exactly.... There's probably only one way to find out....: Put at least one mT -020 RAM on the top left position. I'm about to socket the RAMs on the first board I showed (waiting for sockets to arrive) and I do have some working mT's which I removed from a 800XL.....gotta check if I have at least one -020 version in there. Then I guess I need some software that seriously stresses/tests the RAM.....any suggestions ? Edited October 25, 2017 by Level42 Quote Link to comment Share on other sites More sharing options...
Level42 Posted October 25, 2017 Author Share Posted October 25, 2017 Didn't your original post disprove that conclusion? "On the last one it's hard to see, but ALL RAMs are Samsung -20 type, but the top left is a Matsushita Panasonic -15 type." True. Maybe the Samsung had the same issue as the mTs OR they were just "used" to do this (or it was a manufacturing instruction)...? Must say that I've seen boards with only NEC chips, even at the top left position (lucky bastard owner ;)) so that would go against what I state above, but maybe they started using mTs only from a certain point in time ? Who knows for sure......maybe there is some internal documents about this whole thing ? Anyway....about 90% of the boards I have seen have a different RAM on the top left position....so it definitely is not random and not an exception either. I saw one picture of a board with ALL mT RAMs. But that poor guy had socketed all positions and put in mTs so that doesn't count Quote Link to comment Share on other sites More sharing options...
JamesD Posted October 25, 2017 Share Posted October 25, 2017 (edited) Not a bad suggestion.....weird but not impossible...guess we'd have to know at the lowest level how RAM is addressed and data fetched/written...normally I would say all data bits are read/written "at once" but maybe.....not so exactly.... There's probably only one way to find out....: Put at least one mT -020 RAM on the top left position. I'm about to socket the RAMs on the first board I showed (waiting for sockets to arrive) and I do have some working mT's which I removed from a 800XL.....gotta check if I have at least one -020 version in there. Then I guess I need some software that seriously stresses/tests the RAM.....any suggestions ? I can't see where it would be an issue writing to the chips, it would need to be reading from the chips for then to have an output. But then it would only be 1 bit... and I don't see where that would help any. 8 bits are accessed at a time and sometimes the bit is zero. Maybe it's something simpler like the machine that stuffed the chips onto the boards used separate tubes for the different DRAMs and tubes of 4164s just happened to get loaded there. Edited October 25, 2017 by JamesD 2 Quote Link to comment Share on other sites More sharing options...
+kheller2 Posted October 25, 2017 Share Posted October 25, 2017 What are the date codes on the all NEC boards and NEC Ram chips? At this point, the only unified board are NEC ones? Quote Link to comment Share on other sites More sharing options...
_The Doctor__ Posted October 27, 2017 Share Posted October 27, 2017 (edited) nec was the high quality chip and was more expensive. it was always the upper left chip. it took more abuse than the cheaper chips and was first to take the abuse from the rails and noise.... later other better quality and tolerant chips took that location... all of the other locations were filled with the cheapest crap (mT) etc... the full nec populated board is the most robust. NEC also made the best monitor for the 130XE it gave a crisp sharp display even at 80's columns and cleaned up the vertical bars (noise) very well... short answer the first chip is different by design... Edited October 27, 2017 by _The Doctor__ 3 Quote Link to comment Share on other sites More sharing options...
+SoulBuster Posted October 27, 2017 Share Posted October 27, 2017 deleted Quote Link to comment Share on other sites More sharing options...
Level42 Posted October 27, 2017 Author Share Posted October 27, 2017 (edited) nec was the high quality chip and was more expensive. it was always the upper left chip. it took more abuse than the cheaper chips and was first to take the abuse from the rails and noise.... later other better quality and tolerant chips took that location... all of the other locations were filled with the cheapest crap (mT) etc... the full nec populated board is the most robust. NEC also made the best monitor for the 130XE it gave a crisp sharp display even at 80's columns and cleaned up the vertical bars (noise) very well... short answer the first chip is different by design... Please explain me technically how the first chip on the left position, which has its addresslines and datalines in parallel to all the others "take the abuse and noise" ? What abuse and noise do you mean ? Please also explain why this apparently was not needed on the second (right) bank of 64k ? Edited October 27, 2017 by Level42 1 Quote Link to comment Share on other sites More sharing options...
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