Prehistoricman

Could be RAM, GPU/northbridge, or MCPX. Or some weird hardware failure like a bad joint on the IDE connector There's a slim chance it may be the RAM. Since I've been tinkering with the RAM for the 1.6 upgrade, I was in also a situation where normal BIOSes were unstable with some visual corruption before a freezing yet XBlast was completely stable. Is there a 64MB RAM test out there? To eliminate the MCPX, you can modify and compile XBlast to write some files and read them back. Or maybe it even has an FTP server built in? Not sure. But watch out for v0.59 XBlast OS because it doesn't seem to be reading my HDD. 0.56 works.

What kind of HDMI? My 1.6 is quite a bit fuzzier over composite than my 1.3 but it may be nothing to do with the encoder.

x3.3294.v16plus - works 128MB x2.5035.v16plus.bin - works 128MB evox.m8plus.v16 - can only use 64MB but still works 256k.yoshi.k2005.v16 - works 128MB but it's a debug BIOS For some reason my X3 flashbios now has no video output, not even a black screen. After about 20 seconds the front LEDs go orange. I'll see if I can deselect the extra RAM by resoldering the chip-select points and maybe this fixes it.

u/toinedeman2002 on reddit just did this mod without length matching the CS wires, so it seems their timing is not so critical. That's awesome this is on Hackaday, thanks big F

You can do it, but it's pretty pointless when the normal RAM footprints are there. You can't combine this mod with a 1.0 - 1.5 Xbox to get 256MB because this mod is just using the same pins as a 1.0 - 1.5 128MB mod.

Hmm I did forget to add functional legs to the required items list! I was thinking about that. I almost added a line to the main menu to say that I modified it. It would be good to get an 'official' release from the XBlast dev but it has been 4 years since the last update.

The Theory There are some awesome scans of the Xbox motherboard online for versions 1.1 and 1.6 (they have a sickmods.net watermark). I traced all the signals of a RAM chip and found these results: A0 - A11 address pins are connected to the same pins of the chip under it BA0, BA1 bank select pins are connected to the same pins of the chip under it Same for CK, ~CK, CKE, ~RAS, ~CAS, ~WE, VREF, MCL, and DQS However, the data pins DQ00 - DQ31 are in reverse order The data mask pins DM0 - DM3 are also in reverse order Since both the data pins and data mask pins are in reverse order, we can reverse both and achieve a compatible interface The chip select pin ~CS is unique for each RAM chip After this, I started tracing the ~CS signals back to the northbridge/GPU on the 1.1 motherboard. Then, I found the same pads of the northbridge on the 1.6 motherboard. Luckily, all 4 of the CS pins are exposed on the bottom of the board! At that point, I had to confirm that the 1.6 northbridge wasn't actually incompatible with the extra RAM. The chip is labelled XGPU-B which is unique to the 1.6. Maybe NVIDIA removed the extra chip select logic to save on die area? So I connected up my scope to 2 CS pins of the existing chips and 2 CS pads on the bottom. My expectation was that during the 128MB RAM test, the existing RAMs will be deselected most of the time and so their CS pins would be high. During normal operation, the extra chips should be deselected. I don't have any scope screenshots, but here was my setup with the scope probes and flying wires. That was 3 weeks ago before I ordered the extra chips from China The experiment confirmed the expectation and the rest is history.

Intro Since the beginning of time (2004) it was known that the 1.6 was missing the unpopulated footprints for the extra 4 RAM chips and this made the upgrade impossible. I was thinking recently that if all the signals for the extra RAM chips are still available on the board, we can add RAM to the 1.6 by just connecting all the necessary signals. After the tutorial segment I'll go into why this mod works. I'll also post a video on YouTube at some point. Be warned: this is more difficult that a 1.0 - 1.5 RAM upgrade Tutorial Required items Everything mentioned in the 1.0 - 1.5 RAM upgrade tutorial: https://consolemods.org/wiki/Xbox:RAM_Upgrade 4x 90mm long mod-wire. I used enamelled wire from a transformer. ~8 hours spare time Step 1: flash the modified XBlast OS BIOS XBlast OS (as a BIOS) is super helpful in doing this install correctly. It will boot with any number of extra RAM chips and includes a test for the additional RAM. XBlast OS will not show the 128MB test option on a v1.6 Xbox, so I've gone ahead and rebuilt it from source with that check removed. xblast_os_v0.60.bin Alternative Download Link: https://mega.nz/file/eeAwTZKQ#aaFcbACj3htA6cEtKwoiy1L7uK93o4YwUSqkGBEsUz8 If you don't trust my build, this is the line of code that needs removing: At this point, I suggest booting it up and running the test. The test is under Settings > Tools > 128MB RAM test Step 2: Remove the motherboard from the Xbox Step 3: Place the new RAM chip on top of an existing chip You'll want to solder down the corner pins first to get a good mechanical bond and so that you can adjust the alignment. I do this by pushing down pins 30 and 31 and soldering them down to the chip below. Then I check the alignment of the rest of the pins. If it's bad, then the chip can be nudged into position while reflowing the two pins. Then solder the two pins opposite. Step 4: Push down the rest of the pins Except pin 28! That is the chip select pin and it is unique for each RAM chip. Leave this pin floating in the air and don't solder it yet. Pin 30 is marked on the PCB. The pins come in a kind of ‾‾\__ shape. When you push them down, the whole pin will rotate around this end -> ‾‾\__ . I like to also push down the tail ‾‾\__ <- of the pin to get more contact with the chip below. Step 5: Start soldering all the pins Very little extra solder is required. Use lots of flux. I like the tacky flux that usually comes in syringes. I also like the drag-soldering method. If there's any excess solder, you will get shorts between pins and this extra solder can be wicked away. The new pins won't naturally touch the pins below even after pushing them down. Step 6: Check for shorts and missing connections For the first pass, I like to go in with a microscope and nudge each pin (of the new chip) with a cold soldering iron tip. If the pin moves easily, it is not soldered. Also check for shorts at the same time. If you have the patience (and want it to work first try without frying your Xbox), check for shorts and continuity with a multimeter. I skipped this the first time and got bitten! Best to clean the pins and pads with IPA before checking with the multimeter. Step 7: Add the chip-select wire First, figure out which bank you are adding: Then, find the chip-select solder point: Bank 1 CS is left of the label for C4P10 Bank 2 CS is between the labels for C4R12 and C4R13 Bank 3 CS is left and above the label for C4P21 Bank 4 CS is between and above the labels C4R1 and C3R1 For banks 2 and 3, the chip-select wire can go through the hole to the left of the GPU. For bank 2, 90mm may be too short, so check the wire length and cut it as short as possible. I removed the GPU heatsink to access this hole. At this point, it should look something like this: Step 8: Reassemble and test in XBlast For a quick test, I don't bother with adding the fan, GPU heatsink, HDD, or DVD drive. The test in XBlast should look like what I first posted on reddit: If the Xbox reboots twice and FRAGs, check the bios selection (if you have one available). A normal BIOS will not accept between 1 and 3 extra RAM chips. If the Xbox reboots three of four times (and it's faster than a normal FRAG sequence) check for shorts. This happened to me. Step 9: Repeat for the other 3 chips The first one is the hardest. Step 10: Reflash with your favourite BIOS Some 1.6 BIOSs won't support 128MB. The X3 BIOS works just fine and it's the only one I tested so far. xblast_os_v0.60.bin

Hey guys. It's very real I posted that thread and I'm just about to post another with more pics and a tutorial here.