EOMA68 Computing Devices

An Earth-friendly way to easily upgrade and fix your own computer

Jun 15, 2018

Project update 62 of 75

2.7.5 Samples received - DRAM is OK, Micro HDMI to confirm

by Luke Kenneth Casson Leighton

It’s been an extremely hectic month what with visiting Barcelona for the 8th RISC-V Workshop and finally procuring DDR3x8 DRAM. Card production is finally underway and we now have a realistic target for delivery.


This type of RAM, in the 4 gigabit size, is now extraordinarily difficult to get hold of. Hynix (who by the way are now under investigation by the Chinese government, as are Micron and other foreign DRAM suppliers) doesn’t exactly guarantee supply of 4 Gb DDR3x8 RAM ICs, but if you want them they’re now USD $4.50 each from the Shenzhen Huaqiangbei suppliers.

As outlined in the previous update, a small Taiwanese DRAM company was found, and their Hong Kong stockist just happened to have 2,000 of a 1600 MHz DDR3 x8 4 Gb RAM IC left, at a price of $3.30 USD each, which saves a whopping $4,800 USD compared to the Hynix DRAMs. We asked them for samples: they said no, we don’t want to break the vacuum seals on the batches (ICs don’t like being soldered after they’ve absorbed lots of moisture from the air). We explained that we weren’t exactly going to buy 2,000 DRAM ICs without testing them first, could we put down a deposit: they said no. We asked them if they could hold the DRAM ICs for us, they said yes.

So just before I left for the RISC-V Workshop, Mike found one of his suppliers happened to have the exact same part (and speed grade) as the Hong Kong stockist had, so we went ahead, ordered the last of his supplier’s samples, and Mike’s factory went ahead with the assembly. I arrived back in Taiwan (which took three days due to weather in Amsterdam) just in time for Mike to send two of the ten samples to the flat.

Why only two rather than all ten? Well, that’s down to the fact you can’t get electronic products back into China once they’re shipped out. The last thing anyone needs is for the samples to have failed (i.e., the DRAM not to work), and to have TEN failed boards sitting in Taiwan that have to be re-made at another cost of $2,000 USD. So, as a fall-back position, I asked Mike to only send two of the boards, and if the DRAMs failed it would be possible to remove the failed DRAMs from the remaining eight PCBs and find yet another supplier. Or just use the Hynix $4.50 USD parts.

The good news: both samples booted up perfectly. The even better news: Mike has a new PCB assembly engineer and he did an absolutely superb job. The quality of the soldering is incredible: shiny and everything. He did however tell me - and it is incredibly hard to see because the JAE DC3 Micro HDMI mid-mount type D connector’s pins are only 0.25 mm wide and 0.25 mm apart - that at least two of the ten samples appeared to have bridging. He’s going to see if using a thinner stencil will help there, as it would leave a smaller amount (lower height) of solder paste on the PCB.

What I haven’t yet been able to fully confirm working is the HDMI output. I recall having difficulty getting HDMI output up and running the last time I tried it, and it’s down I think to the fact that in the 3.4.104 fex file it’s necessary to use dual-screen output for some reason. I’ll keep investigating. The layout however looks absolutely awesome (thanks to Richard, there).

Anyway, this is all good news, so we went ahead with the order. Except the Hong Kong stockist went, "oh, we sold them, sorry." Oink. This being Taiwan / China, that basically means that the Taiwanese manufacturer is now extremely embarrassed, because a customer who spent money to test using their product is left in the lurch. So, Mike got on the phone to them in Taiwan, and explained that, after they had promised to hold (and supply) the DRAMs, and those being the last available stock, we’re screwed.

To "save face", the Taiwanese manufacturer, which is based in Hsinchu City (right next door to TSMC’s plant) offered to have a new batch made up, so we have been able to order 4,000 DRAMs to make up 1,000 PCBs. There are only actually around 800 orders, however I do not wish to mess people around with anything less than an order for 1,000 units. That also means that even if there is up to 20% failure on the boards it will still be possible to supply everyone.

Updated Delivery Schedule

It’s going to take about a month to have the 8 Gbit 1600 MHz DDR3 x8 RAM ICs manufactured: we’re on the way. Hooray. It’s been long enough. There is still quite a lot to do: work out a test rig (I may actually go to Shenzhen for that), get the Micro Desktop casework lasercut, the corners made up, get the OSes prepared - a heck of a lot, in fact. All in all, it will likely take three months after getting the cards back from assembly before shipping begins. That puts actual delivery of the first units in late October. All delivery dates have been updated accordingly. You can, as usual, check the status of your order by logging in to your Crowd Supply account.

As always, if anyone would like to help, do join the mailing list. If anyone would like to help out financially, here’s the liberapay link: https://liberapay.com/lkcl

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