[lalle]

Hi,


I currently have 3x O2s (the onlything that seems abundant in Sweden) but only one up and running.


The main issue I and others with O2 seem to face is the scarcity of large ram modules and at some point, it might be the thing that turns the O2s from inefficient space heaters to purely ornamental objects in people's vintage hardware collections.


So my question is, as I haven't found a ready answer by casual googling, what makes the ram sticks different, and is there any chance that new ones could be hacked together as unused ram ICs appear on sites like eBay, FPGAs get cheaper, PCBs gets easier to have made, and things like reflow ovens are much more readily available now than just a few years back.


Thanks for your time and look forward to answers!

[weblacky]

I've done a small amount of research on this.  It's a form of SDRAM (NOT DDR) and I think it's has more legs on the RAM ICs then was common in the PC world.  I think PCs moved to DDR while SGI was still using SDRAM technology but hadn't yet gone to DDR. Though the SDRAM on SGIs moves FASTER than the SDRAM PC66/PC100/PC133 memory used in PCs (before the DDR move).  It's an SGI so obviously it's got parity or ECC technology.

I do not know anything about how RAM really works (and how you do the layout of which there are MANY valid forms/designs). 

Knowing what little I know there would be some form of SPD for timing info programmed into each module.  There does not appear to be that many ICs on the O2 Sticks.

If you're thinking if it's possible to MOD a lower density Stick into a higher density stick, I was wondering if there was only a SINGLE layout among all the sticks, then just change the RAM and the SPD programming (perhaps some passives) and that MAY be it.  However demand is not high enough for SGI RAM to warrant this unless you're already someone who works with RAM design and has this knowledge.

The think the bigger issue is getting the older (high-density) SDRAM chips as normally later-model PC memory never used these chips (it was later SDRAM tech after PCs had moved on).  So you may not find a "stockpile" of this kind of SDRAM IC waiting to be scooped up and used.

Given that high density modules exist, an audit of parts between a low density and high-density module is easily done.  Then you'd know how they may be the same or different.  I'd assume a change in SPD values, but that also isn't totally unknown and you'd likely be cloning a valid SPD anyway (not recreating it).

So the real question is:

1. There are NO SDRAM testers for these chips (I checked), you'd not be able to test them after assembly, outside of using an SGI (slow for production).

2. Is the PCB layout of lower-density modules the same as high-density and you just have to change components and SPD?

3. Can you even FIND these larger RAM ICs for sale anywhere?

4. After assembly, is there enough market for them at reasonable prices to warrant all the work.

If you're going to do an audit, let us know what differences you find, it would be interesting as I've thought of doing this myself...but having to find a working programmer for the SPD AND trying to find a good source for the SDRAM seemed too high a task when really, after about 256MB of RAM, most people don't seem to want to spend the money for more RAM on O2s...due to the lacklistre CPU options. Anything more than 256MB normally doesn't make the OS any faster...it's really application related (like photoshop, softwindows, etc).

So it's not an impossible task, but programming the SPD values will be a project and find parts will be a project.  Otherwise, I guess you just copy what you see?

I should also mention that COPYING/CLONING a module may be fair game but it's going to run afoul of any IP owners that would sue a business trying to sell these clones.

[jpstewart]

FWIW, I found a high resolution photo on-line of some 32MB O2 RAM modules. I was able to read the part numbers HM5216165TT10H and D4516161G5 off the chips. (Same stuff, two different manufacturers.) You can Google for that part number to find the datasheets for the chips and extrapolate some info from there. They are discontinued products, of course. 

If anyone has a higher-capacity O2 RAM module (or photo), find the part number on the chip, get the datasheet, and compare the two.

As weblacky observed, the modules have parity or ECC: there are 9 RAM chips per module.

I haven't been able to get a part number from the smaller (SPD?) chip in the middle of the RAM module.