What's wrong with this Apple IIgs motherboard?

well hello everyone and welcome back to adrian's digital basement i have the apple 2gs on the bench here and that's because i want to do a repair on this apple 2gs motherboard that was sent in for a mail call episode several weeks ago this motherboard has two issues i want to address in this video one is it's got some bad memory you need to try to figure out which chip is bad and swap that out and next it has rom version 0 on it which limits compatibility quite a bit so i want to try to figure out how to update the rom on here now it uses a custom chip so it's not going to be as easy as just swapping in an eprom so without further ado let's get right to it [Music] okay i have my good apple 2gs here on the bench so i wanted to run the diagnostics on this machine first so we can see what a successful diagnostic looks like on the apple 2gs if you recall from the mail call episode the motherboard from mike didn't pass its diagnostics which gave me an idea of a fault it also had trouble running software would crash and do weird things so that was a little bit of an indicator as well let me remove the lid from this 2gs so this one is a little decked out compared to maybe the average one the power supply is a little bit warm it's been running for a bit i have the apple scuzzy card in here and this is the more fancy scuzzy card that actually has dma so it's relatively fast in addition if i turn this off it also has a ram expansion card which how big is this thing four megabytes maybe yeah four megabytes it's funny the original ram expansion card was quite big could only add one extra megabyte to the machine so that plus the 256k on these older ones gave you 1.25 megabytes but of course this little tiny card gives you quite a nice expansion you can find these on ebay relatively cheaply it's marked garrett's workshop for meg's ram i think it was like thirty dollars or something like that an absolute great value i really recommend getting this card there are bigger cards out there like eight megabyte ones but is that really necessary for a 2gs i have the 2gs connected through the open source scan converter here so we're getting an image and therefore we're getting a capture as well i have a keyboard and if we hold down option command which is open apple closed apple control and reset this should initiate the diagnostics here it goes so you'll get this changing patterns and whatnot as it tests the various memory banks and stuff like that switches modes into the high-res 2gs color mode back to the regular apple ii modes at the bottom of the screen you'll see it says zero six thousand seven thousand eight pounds is sort of changing those are the phases of this diagnostic test that's running and we'll take a look at what those mean in just a second [Music] and it ends with a system good okay so that's a working test let's switch to the other motherboard that mic sent and we'll run a test on that one again i only have one power supply so i'll have to be using this one here to test the motherboard from mic all right everything is connected let's power this on no speaker let me grab a speaker just so we can hear that running i'm just gonna use a normal i don't know this is from a monitor or something i always save speakers whenever i see them and i'm sending something to e-waste we're not getting anything because the power supply is not connected to mains power you really do need that to get any operation out of your 2gs okay here we go let's try again okay normal sound and we have check startup device now one thing that's interesting and i wonder if this is something to do with the fact that this is not in a case and maybe it's having a grounding issue because of the shielding does everyone remember that problem i had with the shielding on uh what was it the color classic where the sound didn't work if it wasn't shielded properly and i had to solder some bridges together i also had a similar issue on the apple ii plus the rfi version of the board has some pretty bad ghosting in the image quality and that's because of a split ground plane thing going on by apple i honestly wouldn't be surprised if that's happening here because see this metal shielding that's on the connectors here this in the normal case is actually touching the shielding that's in the case and the power supply is doing the same thing so let me take this power supply and touch it to the metal right here and look at that all of the waviness on the image is gone and when i remove it it's back so that's exactly what's happening here again apple they utilize all that shielding as something that completes the ground plane and right now i have a feeling we have a ground loop happening from this video connector here through the open source scan converter and all the way around very frustrating that happens i'm just going to add a clip lead between the power supply and this metal here to take care of this interference problem okay we're booted back up let's boot into the diagnostics again and see the failure on this board okay you can kind of see a problem right away okay so there's the bad error sound and it's o2 e0 2000 i'm going to write this error code down 0 2 e 0 2000 so i'm going to rewind the footage here but when that diagnostic was running and it was showing a pattern on the screen i noticed that the repeating pattern had little extra pixels that were dark so to speak it was definitely showing up as a bit error that wasn't showing up when i tested it on the good machine so that was sort of a visual indicator that there was actually a problem as well doesn't really help us narrow down exactly where the bad ram chip is but the fact is that this code that just popped up will help us to some extent all right so i googled around looking for documentation for the apple 2gs and i found several very relevant documents first is this apple ii technical notes and is the diagnostic error specifically and this was something that was put out by apple most likely for their dealers to help figure out what was wrong on the board so it talks here a little bit about those error codes that pop up and they're in the format of a a b b c c and d d so looking at the code that i just wrote down a a is 0 2 which shows up right here as a ram test the second two digits is the bank number which is e0 in this case and then cc does talk about which bits failed so that's this that was 2-0 in the test these last two zeros are irrelevant now when it says two-zero what does that exactly mean as the bit failure we'll get back to that in just a second but the next step is to take a look at what is using bank e0 what is that ram specifically so again to google i found the apple 2gs hardware reference manual and it's kind of like the service manual but it's more about how to program the apple 2gs it's not so much about technically how the chips are all connected it's really all the registers and the memory maps and how you're going to use all the advanced capabilities of the 2gs versus a regular apple ii and here is figure 2 3 which is the apple 2gs memory map and sorry it's a little bit blurry this is like a scan from a book and it's it's just not that clear there are two types of 2gs's a 1 meg version and a 256k version the one meg version is the rom 03 version i don't have one of those that has a megabyte of memory on the main motherboard both of the 2gs's i have this one from mike here and my actual 2gs are the 256 k versions so we know that bank e0 is the one that failed and right here it is e0 and there's e1 slow ram controlled by the mega 2. we'll take a look at the actual motherboard here it says standard ram here and it says fast ram here and then this chip right here is the mega 2 and it does say mega 2 right there what the mega 2 is basically is the entire apple 2e except for the processor on a single chip that's right apple basically combined everything together from the old apple 2s into this single chip so it's really what makes the 2gs fully apple ii compatible is it literally has an apple 2e on the motherboard in this chip and incidentally the mega 2 is also used on the macintosh apple ii compatibility card the one that goes in the color classic and the mac lc's it's using a mega too and it interfaces that to the macintosh for like screen updates and i o input and output and stuff like that if we look here at the screen capture we have the mega 2 and it is connected to a chip called the slot maker which allows these slots to work it connects to the 128k of ram which is going to be this standard ram right here which is that bank e0 and e1 it hooks up to a video graphics controller chip which is what gives the apple 2gs the additional graphics capabilities that the regular apple ii doesn't have but keep in mind the mega 2 is what generates all the apple 2e and 2c style graphics and the video graphics controller chip only handles the 2gs modes these extra modes and funny thing is the color display you see on a 2gs when you're in text mode that is actually not generated by the mega 2 the mega 2 is outputting normal apple ii monochrome graphics and text and it is the video graphics controller that is literally taking that and applying color on top of it so say you change your text color to purple well it's white text that's coming out of the mega 2 and the video graphics chip after the mega 2 applies the color and the background color and the border color it's kind of funny that it's that capability was added but it was so the mega 2 has its own ram for running old apple 2e software and then this additional ram over here and what's plugged into that slot are totally used by the apple 2gs specific software and when you use a 65 c816 it addresses all that additional memory with a two byte bank and it's all banked into 64k that's kind of how it's working now if we look down in this section on the board you'll see the additional 128k of ram that's on my particular versions of the 2gs the pfi or fpi chip there that's sort of like the memory controller chip it's also connected to the rom that's on the motherboard and the expansion slot it's sort of handling all of that additional capability that is 2gs specific and hanging off that is the processor as well the 65 c816 so we know from the diagnostics well it didn't maybe didn't get to that point i don't know but i think this ram is okay all of the ram problems exist on the ram that's hanging off of the mega two okay so we've identified that the ram that's problematic is this ram down here but there are four chips here 64k and 64k which of these chips are the problem now from the diagnostic code it said bits 20 and i assume these are hexadecimal bits so 20 hexadecimal are the problem what does that mean exactly apple could have been a lot more specific to say that when you saw a 20 it specifically meant that chip or this chip or even talked a little bit about how the addressing specifically works to these chips but unfortunately they didn't now luckily there are also copies of the apple 2gs schematics online if you just do a google you'll find them and right here on page 2 we have the mega 2 so this is the apple ii e on a chip and it has four of those ram chips that hang off of it and here they are we have um2 um1 um4 and um3 these are typical 4464 drams basically each chip has four data bits 64k each so you need two of them to make 64k of 8-bit memory and there are two and that's really because if you think about the apple ii originally had 64k like the apple ii plus when you had the memory expansion but the 2e and the 2c added a whole extra shadow ram auxiliary bank of memory another 64k that enabled like the 80 columns mode and the double high res and software could bank switch that auxiliary ram in and use that memory for additional storage i've been looking here and the mega 2 which is this chip here has two outputs for cas that's the column address select has a and m i'm assuming m is main and a is auxiliary and i'm gonna make a guess that m for main maps to bank e zero and that a for auxiliary maps to bank e1 and looking at the cas m or main line it runs over here and it goes to these two chips right here so it goes there and it splits off to there and there and that's um4 and um3 if we look at the at the motherboard here it's these two chips on the right so i'm going to put an extra little mark on both of these chips here just to indicate that these are the two that i have a hunch are bad now one thing i know for sure is this machine does sort of work and it only has some small errors in the memory if there were entire data bits that were dead there's no way this computer would even work at all so some of the problems i've seen in the past is yeah like one of the entire bits is just completely dead so instead of eight bits of memory you have seven or six and a computer really can't function because you're not gonna be able to run machine code when you have problems like that so i think the problem is that there are specific bits of memory in the entire 64k which are bad and if we go back to that diagnostic pattern where it was showing the graphics there there were repeating dots that looked bad but certainly it wasn't entire columns that were missing or entire rows that were missing which would indicate more fundamental problems with this memory i have another idea on how to turn that 20 code for bits into some usable information and up here in the windows calculator i've entered in 20 hex and that gives us a bit pattern and we can imagine there are eight data bits 0 through seven right so that's eight and it's saying here that this is potentially the bad bit that's how i'm kind of translating this so that would be bit five if we go back to the schematic here these are the data bit outputs here so zero one two three four and five so um three that hopefully is actually the chip that is bad so i'm going to draw a big circle on it as this one right here so i think at this point the logical next step is to yank this chip out of the board i'll install a socket we'll pop a new one in there and we'll see if this problem is fixed all right the ram chip has been removed here it is right here i have not tested this computer yet so let's see if this thing actually works so first let's test to see what happens if we try to power it up without the ram chip installed at all it will kind of confirm my hunch that it's not going to work at all let's just give it a try okay power up okay very unhappy apple tgs this is what happens it's running it is running but it's very very screwed up i don't have a 4464 chip handy so i'm going to steal one off my vga card here which i know works these are good chips because i use this card all the time there we go the notch is in the correct configuration let's power this up see if this thing works better all right we got the check startup device which is completely expected let's reboot this and let it do the ram test i'll plug the speaker back in so we can hear that horrible diagnostic sound if that does come up the one where there was a problem okay i am seeing that dot still there that means that there's still a problem with the ram there it is so i definitely made a guess that it was this chip that was bad now two guesses right i was guessing on that bit 20 meant it was that bit that was on this chip but the whole which bank was it e0 or e1 i assumed that the cas m meant main bank which would have been e0 but it could well be this other chip here so i'm just going to double check on the schematics to make sure that that same bit talks to this chip here and hope that that's the problem now just as a caveat here i could have just removed all four of the chips or put sockets in and then just figured out which of the chips was bad but i like to understand what the actual problem is and not throw the so-called parts cannon at the motherboard just swapping out parts left and right if we can actually figure out what the problem is now if everything was socketed no problem we just swapped chips out but these require actual desoldering work and every time you desolder you can damage the board so that's the danger all right i'm gonna go check the schematics to see if that same bit uh i think it was bit number five is um on which of these chips for the other bank and i'll take that chip out next all right the next socket is in the schematic confirmed that bit number five was this chip here let me pop in my known good one here i put the original one that i removed and it's back in the socket so that's on the motherboard this was the one that i think might be bad let's see if this is the case let's plug in the speaker again but the computer is booting good sign let's reboot this thing with the diagnostics here we go i'll know pretty quickly if i see those extra dots i think that's it no dots so it was this chip right here so it should run through the rest of the test now yeah i think it's already gotten further than it's ever gotten before oh apple you could have just told us which of the banks e0 was and which was e1 why did you make me have to guess so i guessed and i guessed wrong system good now one thing that's interesting is there was no ramping up test tone that the other one was doing and i assume that's because this is rom 0 and that one is rom 1. so system good means at least this thing should be working now it's time to try to swap out this rom with a new one so this i see here this is the rom now i think it's 128k but the problem is is that it's in the same footprint here that probably maxes out at 64k with a regular eeprom this eprom right here is a 256k eprom 27c o20 i think it is and it's too big to fit in this socket it's got uh i think it has four extra pins and those are going to be address lines so i'm going to have to make an adapter to go from this to this socket and then this should work this chip now of course that means making an adapter with a couple sockets stacked on top of each other and running some wires around you know one of those kind of janky adapters that i do there's probably a pcb based adapter for the 2gs that has like a surface mount chip on it and the pins and it all goes in very easily but i don't have one of those and i want to get this thing upgraded to rom 1 so i can actually run some software on it pretty much nothing really works properly on rom 0 i noticed i tried to boot gs os and it's like it requires rom 1. the rom in the 2gs actually holds quite a bit of the operating system for the gsos os gs os os gsos and that means any game or software that uses those libraries that are built into the rom they just don't work so swapping out this rom is kind of imperative to get this thing working now i could just take the rom chip off the other machine stick it in here but i'd like to get this board working with rom 1. this will be useful for anyone out there who doesn't already have rom 1 on their machine and they're stuck with rom0 and you want to try to use an eprom to upgrade it to rom 1. all right adapters so uh reactive micro sells an adapter you can just go to their website and buy it if you so desire there it is it is a little pcb with a surface mount chip on it and it looks like they made some adapters using stacked rom sockets which is exactly what i'm about to try to do and uh yeah but they don't sell these anymore i don't think i think they're calling this the version 2.0 um so anyhow i need to make one of these stacked adapters and use an eeprom luckily this apple ii box.de they made the instructions that you need uh the only thing is they're talking about using a 27c 1001 eeprom and the eprom that i have specifically is a 27c020 i got a bunch of these chips here look at these tons and tons of these they came out of cisco devices i guess a router i think i look these up and they're 256k each i have one of these in the eraser right now i have on screen here the pin out for the 27co2o compared to the 27c 1001 there's not a whole lot of difference we have pin 30 which is not connected pin one which is vpp but is a19 pin 27 on the motherboard goes to pin 29 on the chip which is going to be address line 14 and that is the same here on the 1001 there's address line 14 and then 15 and 16 are in the same exact position on the o2o chip that i'm going to use so really i'm just not going to connect well i think i'm just going to i'm going to ground pin 1 here which is address line 19 i'm going to ground 30 and 31 which is 17 and 18. i know it doesn't sound completely clear the way i'm explaining it but basically we're just going to wire it up exactly like this but the pins that are in blue here are the ones that aren't going to be used and i'm going to ground all of those well i have this socket which is going to go in the motherboard and then i have these pins here which will plug in and there's going to be two extra overhanging pins while any pin that goes from this into this that i don't want connected that is specifically pin 28 here going to pin 30. i need to cut the pin on here so it doesn't make contact with the pin there and that way i can connect them together to do that grounding i was talking about okay the adapter is complete so the large eeprom that's 256k plugs into the top part and i have little barge wires that rewire it as necessary now i'm glad i didn't just fully trust this thing i found online here for the 27co2o because there were too many address lines on this particular eprom this would make it like one megabyte i think something like that so i'm glad i went and double checked the data sheet so this is the data sheet for for it it goes up to address line 17 and that's opposed to this one which has an 18 and 19. that's the program pin and the vpp pin so when you wire up the adapter you don't actually have to hook those lines up to anything vpp and the pgm line they're only used for programming so you can leave those floating but for address line 17 which is not used on the apple 2gs it only goes up to address line 16 which it's rewiring from this pin here up to there so 17 i do have to ground on the new eeprom on this adapter here otherwise it could accidentally select the wrong half of this eprom so of course you could put two copies of the ram in here like rom zero and one and put a little pull-up resistor with a toggle switch to ground and you could select between the two roms with this but i don't really need to do that because like why would i ever want to run rom 0 and i can't run rom 3 on this motherboard this is not possible only rom 0 1 and 0 0 are possible anyhow so i grounded address line 17 and then the other two are floating and i did the rest of the rewiring so this chip now has been programmed for rom01 so let's install this into the socket here or into this adapter rather oh it's why is it i might have a bed pin here now i did go through everything on this adapter checking to make sure that none of the pins are sorted together the ground goes to the right place that vcc which goes from this pin here goes up to that pin and it's not connected there's a couple spots right there and right there where i had to cut the pins and i just wanted to make sure there's no shorts so anyhow that is all in there correctly and now we have to put this into the rom socket now there is no notch on this socket but there is a marking on the motherboard there with the silk screen and i can just see the notches down here which is opposite of the cpu which has been flipped around and this ram has the notch up as well for whatever reason they put the notch down on the rom chip now if you're not sure about that i'm going to put this in without powering this on and i will check to make sure the ground and the 5 volts are in the right spot on this eeprom there it is the little stack is in the motherboard okay with the chip in with a notch down towards me this pin here this is going to be 5 volts and this pin down here is going to be ground so on the power connector ground is these two pins right here and that is correct and this pin up here is 5 volts which should be one of the other pins not sure which one that one right there there we go so it's definitely not in backwards and that beep when i touched the five volts to ground was just the capacitor on this board all right we're actually ready for some testing now i have everything plugged in just double check the old ram is here the old ram is here and here we go oh no we have no snow nothing so that's weird let's just put back the other rom really quick okay that is uh definitely starting up so there's nothing damaged on the computer i wonder what's going on you know what this socket here unfortunately this one here this is one of the sockets i hate if they just don't make very good contact sometimes so i'm going to put this back in here and i'm going to really push it down hard yep in fact i can see right now that it's popping out of the board so i'm gonna have to take that socket out i'm just gonna push down on it we're gonna turn on the computer and see what happens oh we still got nothing okay i swapped out the socket this is the original socket right here and the funny thing is i could not get this thing to work still it just would not do anything when i had my eeprom in there but switching back to the original rom it worked fine i spent a ton of time double triple checking all my wiring on the adapter i broke out the oscilloscope just to make sure that the chip was reading properly and a good test for that is you stick a blanked eeprom in there and when you do that the outputs of the eprom will be high on every single address and i hooked up the scope to the chip select line so when that went low i expected to see high on all the outputs and i did but when i put in a programmed chip where i programmed it with rom one that i downloaded off i don't know you know one of the various websites i went and got like five different copies of it just to make sure that the one copy i had wasn't bad well when i checked with the oscilloscope all of the outputs when the chip was selected was low which meant the computer what it was reading out of the chip was simply all zeros and when you first turn on the 6502 based computers it goes to like the reset vector which is like fff c or something like that and it reads the address where it should start executing code so you shouldn't have all zeros that's definitely definitely wrong that was telling the processor to go to the bottom of memory to start executing which clearly that's not going to work so that definitely told me that the code that i loaded into the eprom was not right so i started doing further googling looking for roms to download and i found this page here which seems to have a dump of like every 2gs rom we have zero one we have three and i don't know why there's like different versions here different banks i'm not quite sure maybe there's two chips that make up the rom on that later 2gs as opposed to one chip there's also a bt rom whatever that is and an alpha rom so anyhow i downloaded rom 0 1 from here and right away i could see that the code that had just loaded off the disk let me load the other file look totally different so all these like apple 2gs rom these are all different copies of the same rom when i load this notice it just it looks different it's c230a2 and when i open up the actual one here that i just downloaded looks totally different so i'm not really sure what's going on here but obviously whatever the emulators are using which i think is the files i had downloaded for 2gs emulators it's different than what's actually in the rom so those dumps that i just found that i showed the screenshot of there where obviously someone had hooked up one of the roms into an eprom reader and read the content directly out of the chip as opposed to using software on the apple ii to dump the contents of rom into a file which i think is how the other ones were produced so i just programmed that chip and i stuck it into here let's see if this computer now works all right i have the speaker hooked up i am going to power this up and let's listen for that bong or dong or whatever the noise that the 2gs makes when you turn it on here we go oh there it is rom01 showing up on the screen it actually works let's reboot that computer one time again this is weird i don't remember ever seeing this before enter the control panel for one set system standard so 50 or 60 hertz oh i just realized now what i was doing i wasn't pushing open apple control reset i was pushing closed apple control reset i honestly did not know that that was how you could get the computer to run at 50 hertz let's just hit three and see the computer running in pal i guess and there it is it's running in pal look how big the border is on the bottom wow but you can switch back by doing that same sequence again so we're going to do 60 hertz two and that swapped over into 60 hertz all right let's just run the diagnostics one more time with the rom01 maybe it's a more thorough diagnostic or something like that see what happens there we go system good and it made that tone so that obviously is rom dependent okay let's run some software on this machine just to really put it through its paces i'll use the floppy emu for that i have some 2gs software on this i will put in my ram expansion card into this thing because some stuff needs more memory than the built-in 256 here okay 16-bit let's see i think let's load gs os all right here we go you can ignore that jitter that is the capture device it is not set up to capture the pixel clock of the apple 2gs specific modes when the 2gs switches between apple ii and apple 2e graphics modes and the 2gs mode the pixel clock actually runs at a different speed it's slightly different output and it's funny as it switches the monitor here blanks out i think it might blank out a little bit on the capture as well but that's what's causing this jittering but system 6.02 this would not load at all before when the ram was bad and then um and i know it also would not work without rom zero it's definitely required for any system past version 4 i think anyhow we have a working machine here so there it is i booted the system disk and yes if you haven't seen the apple 2gs operating system it's not bad it's really not bad and don't forget that this is all running on a computer that's like two point something megahertz that's it and yet it's it's pretty functional it's definitely on the slow side like notice when i update this uh window how long that takes to draw like if we move it off screen move it back it's not exactly great but it does work and when you have an accelerator on the machine it's pretty fantastic how actually fast the apple ii is incidentally here's the memory here total memory 4352k so this game is actually booting and notice it's using the welcome to the 2gs screen here so it's actually loading the gsos some of those routines are in rom so that helps not take up memory on the machine that can mean that this game may not work without rom zero one fun time arcade there it is while we wait for this to load i am going to stick a label on this rom chip apple 2gs rom 01. speaking of loading that's one of the things about the 2gs i mean i had one of these computers as a kid what's pretty annoying is that things took a long time to load a lot of times at least off the disc drive i mean the three and a half inch apple disk drives weren't terribly slow but these games just seem to be very inefficient at loading i don't know what it was it just took a really long time some games like still feed from sierra was unbelievably slow and yet to swap discs around luckily games like this one i think because it showed that welcome to the 2gs screen i think could be copied onto a hard drive so i did have a hard drive um as a kid i got one later it was 20 megabytes external hard drive and it made these games a lot more playable than when you're doing them off disc constantly but i think there was a lot of trial and error to oh here it is it just loaded up there's a lot of trial and error to figure out what actually worked off the hard drive and what you had to boot the disc games were cracked you know it was all over the place it wasn't super easy should be sound [Music] okay there was music and i aborted out of it so there it is arkanoid looks pretty good remember as i said two point something megahertz this machine whoa nice 60 frames per second um oh i got the laser oh and i just died nice smooth animation there's that music as well this thing has like a and sonic synthesizer chip in it so pretty capable sound so the apple 2gs it was quite a capable machine that apple hamstrung by giving it not enough megahertz there are lots of other videos talking about that i'm maybe i'll make a really nice retrospective on the 2gs one day as it was one of my favorite computers well up until i got my amiga and that became my favorite computer i went from the 2gs to the ibm pc at the same time and then i got an amiga and i loved my amika 2000 i had an accelerator in there skuzzy hard drive flickr fixer so i could output 31 kilohertz video that the amiga was an amazing computer and it got me through college um then pcs took over with windows 95 and you know the rest is history but for many years i loved my 2gs and it was very capable in many ways i had the transwarp gs as well back when those were they were actually affordable for the machine and i couldn't believe how fast it made the computer just unbelievable but then the amiga of course you know blows away the 2gs with all the processors and i think the amigas you know similar age to this right this came out in 86 and so the amiga the amiga was leaps and bounds ahead of this thing of course though you didn't have that backwards compatibility with the mega 2 chip as we talked about so anyways different machine and a different subject so that is going to be it for this video the repair and upgrade of the 2gs motherboard from mike thank you very much mike for saying that in and of course uh thank you very much brett for sending in these eeproms as well it's great to have these because actually don't have a single other eeprom of this large size and this made this upgrade possible oh something else i forgot to mention so these two chips here on the left that's bank e0 and these two chips on the right is bank e1 so if you have bad ram and it's saying e1 it is one of these chips and decode the bit as i showed you with the calculator and then you look in the schematics to figure out which of the two chips it is because four bits are on one and four are on the other so hopefully that knowledge is helpful to someone who's in the future repairing their 2gs and then don't forget if you're going to make a rom adapter like i did you got to use the right images otherwise you're going to be stuck with a machine that doesn't work just like i was of course i will put all the links for the stuff that i worked on and showed here in the description below if you like this video i'd appreciate a thumbs up subscribe all the usual stuff don't forget to check out my second channel and a huge thanks to my patrons whose names are scrolling up the side of the screen so that is going to be it stay healthy stay safe and i'll see you next time bye bye you

Channel: Adrian's Digital Basement

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Id: 8StiTHiYlvQ

Length: 41min 36sec (2496 seconds)

Published: Sat Jul 31 2021