Here’s yet another article in the IBM System x3550 M4 series, I decided to upgrade my trusty M4’s memory.
Back in 2019, I picked up an IBM x3550 M4 7914 to use as a VMware host in my home lab. The system came to me with just 24GB of RAM in six 4GB modules.
The x3550 M4 has 24 DDR3 SDRAM slots, supporting up to 384GB in 24x 16GB ‘RDIMM‘ modules or 768GB in 24x 32GB ‘LRDIMM’ modules.
The M4 supports a wide variety of size and rank configuration, from 2GB single-rank modules up to 32GB quad-rank modules. To use all of the slots, you have to have both processors populated, and you can’t mix regular ‘RDIMM’ and ‘LRDIMM’ modules.
The six original memory modules were IBM branded, Micron M393B5273DH0-YH9 4GB PC3L-10600R modules, and for a time, they did the job.
But not too long after I got the system, I purchased four 16GB Hynix HMT42GR7AFR4C modules for $105. At the time the 16GB modules were a great price point – good value for the density, and the best value per gigabyte. The price of 8GB modules was roughly the same, per-gigabyte, so it made more sense to purchase the larger 16GB modules, leaving more slots available for future upgrades.
At the time, the 32GB modules were about three to four times the price of the 16GB modules, presumably since they were the ‘LRDIMM’ modules. Supply on eBay of the 32GB modules was sparse, so perhaps it wasn’t originally a very popular option.
I was able to mix and match the old 4GB and new 16GB modules together, bringing the system up to 88GB of RAM.
About three months after that, I found myself needing to run a virtual machine with 128GB of RAM. So I purchased another four 16GB modules from the same eBay seller for $92, now bringing the total up to 152GB of RAM. It probably wasn’t the most performant of configurations, mixing the old and new, but it honestly did the job. And for quite some time, too. I was able to use that configuration for about 3 years.
In August of 2022, my needs again increased, needing to run another few VMs with increased memory footprints, so off to eBay I went again and found a good deal on eight of the very same modules for just $106. Again, they were a really good value for the size and matched the existing modules I already had. This time though, I removed the older 4GB modules and just ran with the sixteen 16GB modules, giving me 256GB of RAM. This worked great for my workload and I was quite happy.
Then in early 2023, while performing the ‘final’ CPU upgrade on the system, I decided to fill the remaining memory slots, and found that DDR3 prices had plummeted, so I was able to pick up yet another eight 16GB modules, again matching my existing ones, for a paltry $53.
The IBM part number for a 16GB, dual-rank, 1.5v, DDR3, 1600MHz RDIMM is ’00D4970′. There appears to be several manufacturers whose products were branded with this part number. Here are two, there are perhaps more.
- Hynix HMT42GR7AFR4C-PB
- Micron MT36JSF2G72PZ-1G6E1HI
The 32GB modules were still outside of my justifiable price range, as I would have needed to replace all of my existing RAM with them.
Author’s Note: As of the writing of this article in late 2024, the 32GB LRDIMM modules are ~$10-20/each in single-unit quantities, whereas the 16GB modules are ~$5-7/each in bulk quantities. The price/value ratio may be better now, but it rapidly gets into the territory of… “Does a 10+ year old system really *need* to have $240+ worth of RAM stuck into it?” As it stands, I only use ~50% of the 384GB in the system when it is running all of my VMs all at once, so there isn’t much of an argument for upgrading the system further. Perhaps I will re-investigate the question in a few years when the prices fall to their lowest point (which may be right now) but before they start climbing again due to scarcity.
The price evolution over time is rather interesting. In 2019, 16GB DDR3 RDIMMs could be had for $26.25 each, or $1.64 per GB. The second purchase in 2019 was roughly the same, $23.00 and $1.44, respectively. Then, in 2022, the very same modules were about $13.25 each, or $0.83 per GB. And then finally in 2023, only $6.63 each, or $0.41 per GB. Over approximately 4 years, the price was only one-quarter of its starting price.
There is something rather satisfying about filling all of the RAM slots on a system – a kind of catharsis that says “There. This is finished. Complete. That-which-could-be now IS.” There is also a weird feeling, as someone who has been in and around computers as long as I have, to say that I have 24 memory modules of *any* sort and to have three-hundred-and-eighty-four GIGABYTES of MEMORY in a system that I don’t even consider my main PC. A system that I use for testing and messing around. Its one thing to see those numbers on a purchase order for a big system for work, and it’s another thing to hold that much silicon in your hand.
So just like I said in my last CPU upgrade article, my venerable M4 is starting to get quite old, but it fills my needs for now. With that said, I think my M4’s upgrade days may be at an end.