One and half decade ago I had an black IBM Thinkcentre tower. The specs were:

  • Pentium 4 2.66 GHz
  • 256 Mb IBM RAM (which later got upgraded into 512 Mb RAM),
  • 40GB HDD,
  • XP Pro SP3,
  • GeForce 2 MX 400.

What interested me was the original IBM RAM that came with it. According to my uncle, the pin layouts didn't match any DDR pin standards.

Perhaps it was designed that way? Is IBM known for making such tricks? What could the RAM possibly be?

My uncle says, He threw it away, although he isn't 100% sure.

Edit: I still have the case:

Identification Badge

Serial Number On The Back

  • 4
    If you still have the sticker, perhaps you have the model number? A Pentium 4 could have used RDRAM although I think 2.66GHz Thinkcentre models used 865-series chipsets which used standard DDR SDRAM. Jul 9, 2019 at 14:44
  • 2
    Nice, but without the model number it's rather pointless to look for information. AFAIR the back then a30/a50 models all used standard 184 pin DDR modules, so nothing special - after all, the (core) hardware was plain Intel design. - Also, the question is a bit borderline, as that isn't really retro in any way.
    – Raffzahn
    Jul 9, 2019 at 14:46
  • 1
    No, the amount of RAM doesn't make or brake - it's about being old and outdates. Even more so, as 256 MiB was the minimum setup for that machine, it could be filled with up to 4 GiB ... quite past your 1 GiB :)) Check here for typical spec of the Thinkcenter tower lineup back then.
    – Raffzahn
    Jul 9, 2019 at 14:49
  • 3
    IBM has been known to use non-standard memory connectors in specific situations (e.g. PS/2 Model 80 system board memory), but I can't think of any reason they would have done so on a ThinkCentre system. The only thing that comes to mind is that this particular system was using RDRAM which wasn't "non-standard", it was just a different standard from DDR. Alternatively, it might have been using DDR2 rather than DDR which would also account for the pin difference.
    – Ken Gober
    Jul 9, 2019 at 14:52
  • 1
    Really non standard pinouts - sometimes very non-foolproof! - did exist in non-PC workstations (Some SUN workstations and their Video RAM that physically fits the main RAM slots but will blow up if you plug it in there. SGIs R3000 systems. etc) .. and as mentioned in other comments, in some 386 era systems... Aug 6, 2019 at 22:05

1 Answer 1


The product ID on the sticker (819475G) identifies the machine as an IBM ThinkCentre A50p, model 8194.

A search for the 8194 model on a few RAM sellers' websites gives us the following information:

The IBM ThinkCentre A50p 8194 Computer takes the PC2700 DDR SDRAM DIMMs.


Memory Speed options: PC2700 DDR333 184Pin SDRAM DIMM

These are industry standard DDR1 parts.

The pinout of DDR RAM (184 pins) was different to its predecessor SDRAM (168 pins), and DDR2 RAM used a different pinout again (240 pins). Perhaps your uncle found that the ThinkCentre's RAM was incompatible with the RAM used in other (SD or DDR2) systems, as opposed to being actually non-standard.

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