RAM upgrades for the original XBox have been a popular mod — you could relatively easily bump your RAM from 64MB to 128MB. While it wouldn’t give you any benefit in most games written to expect 64MB, it does help with emulators, game development, and running alternative OSes like Linux. The XBox PCB always had footprints for extra RAM chips, so RAM upgrades were simple – just get some new RAM ICs and solder them onto the board. However, in the hardware revision 1.6, these footprints were removed, and RAM upgrades on v1.6 were always considered impossible.
[Prehistoricman] brings a mod that makes RAM upgrades on v1.6 possible using an old trick from the early days of home computers. He’s stacking new RAM chips on top of the old ones and soldering them on in parallel. The overwhelming majority of the RAM lines are shared between chips, which is what makes this mod possible – all you need to connect to the extra chips is magnet wire for extra RAM chip select lines, which are, thankfully, still available on the board. He shares a tutorial with plenty of illustrations, so it should be easier for you to perform this mod, in case you’re stuck with a newer console that doesn’t have the RAM chip footprints left onboard.
We just covered an original XBox softmodding tutorial, so this is as timely as ever! If you’re looking to read about the 128MB mod, this is a good place to start.
We thank [DjBiohazard] for sharing this with us!
I stacked RAM in TRS-80 days and later in Atari-ST. Seeing that done today gives me a wide smile!
;-D
I remember doing this for a friend back in the day. The donor board was mine that had suffered a lightning strike that killed the CPU, but the RAM was still alright. I’m amazed that I was able to solder that at the time, smallest thing I had worked on up to that point. We also bumped him up to a massive 120Gb hard drive and a better fan, and of course the required LEDs everywhere. Halo 2 ran like a dream from the HDD and I vaguely remember some XBE patches that let it use more memory.
“He shares a tutorial with plenty of illustrations, so it should be easier for you to perform this mod, in case you’re stuck with an older console that doesn’t have the RAM chip footprints left onboard.”
*NEWER* console. 1.6 was the last revision, older xboxes have extra footprints for more RAM.
yeep, fixed!
Watch the price run on the 1.6’s on eBay, if the non aware can work out which is which without using a screwdriver.
Why stop at 128? If you’re stacking, might as well make some fat stacks! What’s the limit on chip select lines?
4 CS Lines. 128MB is the absolute MAX
Is this true even on the older revision boards? If a aftermarket mod chip like the new Celebios mod with all the possible I/O add-on’s the developers intgrated for future updates. Could that chip, or similar mod somehow add a processor to add 4 more CS lines so 256mb could be possible? I’m newer to electronics, maybe the CPU Is what limits the amount of CS lines? I can’t remember, but In a P.C mother board. Is it the M.B or the CPU that controls the amount of PCIe “lanes”
No, the CPU is not what limits the number of chip select lines. The Pentium 3 architecture does not have an integrated memory controller, the memory controller is external to the CPU on the custom nForce chipset in the Xbox. Intel wouldn’t have a desktop processor with an integrated memory controller for another 7 years with Nehalem and their Core i series in 2008. AMD had an IMC starting with the Athlon 64 in 2003.
And no, it is not possible to add more chip select lines than what exists already. While the x86 address space is 4 GB, and is extended to 64 GB using PAE (with the limit no single process can use more than a 4 GB chunk), the amount of physical memory is entirely limited by what the memory controller in the chipset can address.
As for PCIe, the number of lanes is decided by the CPU and chipset. The number of lanes can be artificially increased by using PCIe multiplexer chips, like a PLX, but the additional lanes are bandwidth constrained by the upstream lanes. But just because a CPU and associated chipset have X number of lanes available, doesn’t mean that motherboard vendors are required to use all of them, or make them available for use.
A new meaning on “RAM STACK” 😁
Stacking QFP chips, that’s some pretty hardcore soldering there….