A while back I ended up discovering this thread upon learning what could be done I thought it would be neat
to pull off such a modification to my PU-18. Being as the more memory available I'd have access to programs
such as e.g. PSXLinux, or larger programs, or if I'm not mistaken even debugging capabilities, of course, one
would have to inject them into their software, or for instance allowing Music 2000 to have access to the additional
RAM installed assuming a patch wouldn't be required or even if it did. Despite the potential benefits listed, I was
unable to track down the four KM48V2104AJ-6 without the shipping cost is an exorbitant amount of money. Instead
of acquiring them I opted to patiently wait for someone to come up with an alternative. Months had passed and not
long after making this decision Alexander_H found what appeared to be a working replacement. What Alexander_H learned was one could theoretically desolder the four KM48V2104BS-L6 acquired from a 16 MB EDO-DIMM 144-pin
3.3V 60 ns Samsung KMM466F213BS1-L6. As it did meet the credentials those of which were: Voltage Rating, Refresh Cycle, and Memory Capacity. Since it matches the requirements the experimenter could swap out the default RAM
chips with KM48V2104BS-L6.
I decided my console would undergo the same operation since Alexander_H had success using the RAM module.
With that said I managed to snag one off of eBay for a responsible price. When it made its arrival I read on how
I could remove the RAM chips someone suggested getting the Soldering Iron and heat up the IC's legs while slowly
prying it up with very little force to prevent any damage from occurring. So I followed this method while trying to be vigilant. However, I accidentally ripped off some of IC109's pads while the other three KM48V514BJ-6 pads thankfully remained unharmed. I'll admit this procedure was not the best and the proper way of going about it is to use a Hot Air gun along with a pair of Dentist Excavator or S/S Tweezers. For the process I of desoldering the individual
KM48V2104BS-L6 I knew I couldn't make the same mistake twice. So I invested in the X-TRONIC 6040 - 2 in 1 Digital Hot Air Rework Soldering Iron Station after complicating for awhile. I'm glad I purchased It because it has made tasks like these a breeze since it took little effort whereas compared to the other method. After I separated the KM48V2104BS-L6 from the Samsung KMM466F213BS1-L6 EDO-DIMM as shown in this photo
and this photo
as well. I used the High-Res photo's pieced together and extracted from the PU-18 service manual that I found from where I don't remember. This allowed me to trace the remaining IC109 pins
I needed to locate underneath PU-18
RAM/CPU pin outs due to nonexistent pads.
When I thought I was officially done and reassembled the unit halfway it proved to be problematic and only displaying
no signal or picture if you will
. I researched what could be causing the issue and to no surprise, as Trimesh
wrote in various threads from assemblergames Fuse PS604 was likely blown. So to be sure I tested with my Multi-meter and only one side was reading 3.5V while the other gave 0V reading. I was fortunate in that Trimesh offered to
supply me with some for the cost of shipping which was extremely cheap when compared to other sources. When the package arrived from Trimesh I replaced the Fuse to only be dawned by the blank screen
. At this point, both Wisi and Trimesh brought to my attention that I should check my wiring as they may be bridging each other. I did as they suggested checking each IC9 pin for shorted connections between the CPU and continuity for bridged wires. Sure enough, the main culprits were DQ26, DQ27, and A9 being bridged as suspected here's proof image
. Afterward, I corrected this by applying a tiny amount of solder to decrease their chances of crossing over one another and double-checking my other wires. I no longer was doomed by the blank screen I was once more greeted with the startup logo. Oh, the joy I felt
knowing I revived my console after cutting it's life short too soon.
Now after having confirmation of its status I reassembled the console, reinserted my Xploder FX Cartridge JP flashed
with Caelta v0.34 along with my my parallel cable connected which feeds to my Startech PCI Express Parallel Port
Adapter Card PEX1, executed catflap on Win7 in CMD with entering catflap /XT:POx0378 run MAIN.EXE ran the RAM
test software by Trimesh to only come across a Bus Error
. Alexander_H created a fix however I am unsure
where I should inject this line of code: #define STACKSLACK 0x12800. So I would no longer get such an error anymore. I've compiled and tested the majority of the samples included from the PsyQ SDK which I experienced a couple of
crashes. while games of course work flawlessly like one would expect.
Anyhow, I've discussed implementing the idea of piggybacking an extra set of four additional RAM chips to double the amount of RAM among Wisi and Trimesh. But have yet to initiate the steps that are needed. I'd like to commence this although I'm curious as to what's your take on it Shadow or SMF on this matter? Supposedly one of the Arcade units had 16mb of CPU RAM. However, I've never seen anymore then 4mb max installed at one time being the /RAS lines or banks only had 2mb each. Perhaps the CN51 on Namco's System 12 COH-700 board allowed more memory to be installed since you can see traces the required connections leading from CXD8661R CPU to the KM416V1204BT-L5 RAM chips.
Thank you so much
Alexander_H for experimenting with the possibility of resourcing other RAM modules that are compatible. Also, I want to thank Trimesh for writing the guide, for shipping the necessary parts to repair my console for cheap, and for helping me troubleshoot my console as well as Wisi of course which eventually lead me to resolve the no display issue because of the two Data In/Out pins bridging each other due to wires touching.
What I had hoped to accomplish from this is that for anyone who cannot find any KM48V2104AJ-6 for a responsible price you can do what I did the correct way of course or contact Trimesh and have him or her ship some to you for barely anything.