CPUWIZ Posted February 16, 2021 Share Posted February 16, 2021 I am curious if anyone would be interested in posting pictures or manufacturer and chip data, of different RAM chips found on 7800 motherboards? And if they are socketed (if no pic available). Could be valuable info, for any hardware designer, that survives the moroncalypse. Random fresh one, I pulled (no socket mobo, got it bare)... Quote Link to comment Share on other sites More sharing options...
Shawn Posted February 16, 2021 Share Posted February 16, 2021 I have a few, I've posted some in the Concerto thread but I'm sure I have more. Quote Link to comment Share on other sites More sharing options...
+DrVenkman Posted February 16, 2021 Share Posted February 16, 2021 Here are the two I have. The first is my AT84 machine, the second is my A1. Quote Link to comment Share on other sites More sharing options...
+-^CrossBow^- Posted February 16, 2021 Share Posted February 16, 2021 Had I know there was interest in this, I could have been doing this all along with all the 7800s I've found. Let me go through my pics from client service work and see if I have any that show the ram up close enough to share. I've seen many different brands and I know they are different speeds as well. I've often wondered if the ram speed differences in the variants is part of the hardware issues we find, especially with the extra timing circuit since I can literally see a game work or not work simply touching that cap into circuit without resetting or power cycling the console? 1 Quote Link to comment Share on other sites More sharing options...
+-^CrossBow^- Posted February 16, 2021 Share Posted February 16, 2021 Okay... I just went through the pics I was able to make the manufacture and chip PN from and here are the ones that are unique that I was able to find in my records. The odd thing is the Sony chips apparently have at least 3 different speeds being used and as a result a different resistor attached as well with one of them having a 370Ω and most having a 100Ω. Most of the ones in sockets were earlier '84 revision boards. Also these are different sizes as the original pics I cropped these from are different sizes or taken from different distances to respect of the original pic I cropped them from. I think the pics are enough to show which were in sockets and which were not, also I would say I usually see them more often with resistors tide off ground to the write enable pin on the bottom chip. On those that have the resistor bodged in, the trace to that pin on the bottom has been severed at the factory. Goldstar - Seen these on mostly newer revisions. Hitachi in an older '84 revision board. Another Hitachi in an older '84 revision board but different speed. Samsung. Soldered in with a 100Ω? resistor Motorola, I don't believe this was actually socketed originally and was one I replaced thinking it might be bad. No resistor Motorola in sockets with a resistor NEC - I don't see many with this brand of RAM on them but they are out there. No resistor OKI - Seen a few of these on middle '87 units usually. No resistor on this one and soldered in. OKI again that is soldered in but with a 100Ω? resistor I believe. RCA - I've seen these mostly on older (Possibly original '84) units. Socketed RCA socketed again but this one didn't have the resistor on it. Sony -10L with the 370Ω resistor. Soldered in. Sony -12L with a 100Ω resistor and soldered in. Sony -15L with no resistor and soldered in. UMC - soldered in with no resistor. 3 1 Quote Link to comment Share on other sites More sharing options...
gambler172 Posted February 16, 2021 Share Posted February 16, 2021 (edited) Oh i have lots of proto bios Edited February 16, 2021 by gambler172 Quote Link to comment Share on other sites More sharing options...
CPUWIZ Posted February 17, 2021 Author Share Posted February 17, 2021 Wow, thanks Jesse. Sick variety of speeds. 2 3 5 10 12 15 WTF? FYI, the resistor is connected to the write enable line. Why only on one is a bit weird, maybe they had a collision of some kind and put a pullup on one. It probably doesn't matter which one it is on. Quote Link to comment Share on other sites More sharing options...
+-^CrossBow^- Posted February 17, 2021 Share Posted February 17, 2021 Yes I mentioned that the resistor was attached to the WE pin on the chips. I thought the different values seem to correlate with the speeds so faster chips like the Sony 100ns has that 370Ω on it whereas the 120s only have the 100Ω on then many of the 150 - 200 do not have it. Quote Link to comment Share on other sites More sharing options...
+Mitch Posted February 17, 2021 Share Posted February 17, 2021 Have you seen the RAM daughter-board that is on a lot of the PAL 7800s? I thought I had a picture but can't seem to find it at the moment. Mitch Quote Link to comment Share on other sites More sharing options...
CPUWIZ Posted February 17, 2021 Author Share Posted February 17, 2021 3 hours ago, Mitch said: Have you seen the RAM daughter-board that is on a lot of the PAL 7800s? I thought I had a picture but can't seem to find it at the moment. Mitch No, I know nothing about the PAL machines. Love to see it though. Quote Link to comment Share on other sites More sharing options...
rj1307 Posted February 17, 2021 Share Posted February 17, 2021 12 hours ago, Mitch said: Have you seen the RAM daughter-board that is on a lot of the PAL 7800s? I thought I had a picture but can't seem to find it at the moment. Mitch I have this version, but I'm not at home right now, so I'm pasting photos borrowed from the internet: 1 Quote Link to comment Share on other sites More sharing options...
CPUWIZ Posted February 17, 2021 Author Share Posted February 17, 2021 6 hours ago, rj1307 said: Thanks. That looks like it was designed with expansion in mind, looking at the extra pins and select line jumper pads. Quote Link to comment Share on other sites More sharing options...
rj1307 Posted February 17, 2021 Share Posted February 17, 2021 Or they adapted memory chips that they had a lot in stock to save money Quote Link to comment Share on other sites More sharing options...
+Mitch Posted February 18, 2021 Share Posted February 18, 2021 The pictures that RJ posted are what I was thinking of. I pulled my PAL 7800s apart and they both have the same RAM chip model just different date codes. The one with the riser board must be one of the 7800s I had on loan to Curt. Not sure if I will ever see those again or not. Mitch 1 Quote Link to comment Share on other sites More sharing options...
Lynxpro Posted February 18, 2021 Share Posted February 18, 2021 On the subject of the riser card, did the French models have a riser board for SCART? Maybe I'm confusing what I've seen before in pics elsewhere with these RAM risers. Odd. Quote Link to comment Share on other sites More sharing options...
+Mitch Posted February 18, 2021 Share Posted February 18, 2021 1 hour ago, Lynxpro said: On the subject of the riser card, did the French models have a riser board for SCART? Maybe I'm confusing what I've seen before in pics elsewhere with these RAM risers. Odd. Yes, there was a riser board that replaced the RF modulator. It had an Atari ST 13 pin monitor port on it. That model 7800 shipped with an ST to SCART RGB cable though. Mitch 1 Quote Link to comment Share on other sites More sharing options...
Lynxpro Posted February 18, 2021 Share Posted February 18, 2021 16 hours ago, Mitch said: Yes, there was a riser board that replaced the RF modulator. It had an Atari ST 13 pin monitor port on it. That model 7800 shipped with an ST to SCART RGB cable though. Mitch But it wasn't really analog RGB output, was it? My understanding was that it was whatever SCART's version of Composite was. Quote Link to comment Share on other sites More sharing options...
+Mitch Posted February 18, 2021 Share Posted February 18, 2021 19 minutes ago, Lynxpro said: But it wasn't really analog RGB output, was it? My understanding was that it was whatever SCART's version of Composite was. No, it was an RGB signal that was output. Mitch Quote Link to comment Share on other sites More sharing options...
CPUWIZ Posted February 19, 2021 Author Share Posted February 19, 2021 2 hours ago, Mitch said: No, it was an RGB signal that was output. Mitch And you don't have one? Quote Link to comment Share on other sites More sharing options...
+Mitch Posted February 19, 2021 Share Posted February 19, 2021 I have two of them. One that was on loan to Curt and the other has the Atari warranty sticker over the screw hole that I didn't want to break. Mitch 1 Quote Link to comment Share on other sites More sharing options...
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