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How do I find documentation about a circuit board?

Q: how do I find manuals and documentation on various circuit boards? I have done searches on some of the markings, but did not find any information.

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Hi! I am working on a little project to expand fast storage for a 2009 Mac mini, hopefully through eSata. I already have a working eSata cable running out the back of the computer. Ports available: USB2, FW800, and one eSata cable. I also have a large USB3 case that does not work well (have to run it as USB2, and drives tend to disappear after a few days). I took it apart to see what I could re-use, and found out the bridge board has an eSata port on it (intentionally hidden by the manufacturer) and some switches.

I would like to figure out what those switches do (RAID switches? something else?) as well as get details on the eSata port. Below are images of the front and back of the bridge board. My general question is, what do I look and search for - and where do I search (special site?) - on a given circuit board to find documentation about it?

Here is the front and back of the bridge board. How would you track down documentation about it?

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Also, the case has two of these bridge boards as well, supporting 4 hard drives each. Any way to find documentation on this?

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And finally, regarding the overall project, the 2009 Mac mini motherboard does not support Port Multiplier, so any bridge board I use will either have to do its own Port Multiplier or have built in RAID to present the disks as a single disk. I am still a bit confused about Port Multiplier, especially in cases where the motherboard does not support it. Can you get bridge boards that support Port Multiplier when the motherboard does not? For example, I was thinking of getting this board (Walmart: SATA Hard Disk Adapter Card 1 to 5 SATA Multiplier Riser Card Splitter JMB321 Chip) which I *think* would allow me to plug in up to 5 SATA hard drives into the board, and plug the that into the motherboard. I was taking this case apart to see if I could swap out its bridge board with the one above, and get fast eSata storage to this old Mac.

Thanks for reading about this project, and for any advice you have!

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Maybe @danj can help with this one.

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Sorry I don’t know of any source for your exact circuit board. Many companies hold their designs quite close as an example Apple never released any of the Mac Mini logic board schematics or board views (as far as I know)

As to what you are trying to do, bridging has its limits! The connection bandwidth for the link doesn’t really increase from the input side (four SATA ports) to the output side (eSATA). So having a SATA III (6.0 Gb/s) drive (a modern SATA SSD) which is able to drive the link at the full data rate won’t improve the throughput if you RAID’ed the data across multiple drives. As the link is already at its saturated state (6.0 Gb/s)

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RAID made more sense with slower HDD drives which unlike SSD’s often couldn’t get beyond 3.0 Gb/s sustained! Then if you are writing data it was even slower!

Thats not to say RAID is not beneficial! It’s the size of the downstream connection. So in your case its 6.0 Gb/s the limits of the eSATA connection. Thunderbolt2 and Thunderbolt3 both offer higher data throughputs Thunderbolt Inteface

So lets get back to your Mac Mini, as while your eSATA RAID case is able to run at SATA III (6.0 Gb/s) your systems SATA port is only able to run at SATA II (3.0 Gb/s) Mac mini "Core 2 Duo" 2.66 (Late 2009), even a single SATA III drive will have issues.

So we get into pouring 2 gallons of water into a one gallon jug problem! While the RAID interface is designed to run at a higher data rata the system just can’t take it all in.

Here we can simply use a single SSD drive which is able to interface to your systems internal SATA interface which is able to saturate the link (modern SSD) and also face the same problem.

Now what you use here is important! You can’t use just any SSD! Just like how the RAID case is designed to run at SATA III (6.0 Gb/s) most SSD’s today are fixed SATA III (6.0 Gb/s) interfaces these days as the need to support older slower systems is just not there and the added cost of the needed circuitry in a highly competitive market doesn’t make sense either.

As it turns out there are still a few auto sense drives Samsung being the most popular! The Samsung 860 EVO SSD offers this ability! Reviewing the spec sheet we can see Interface line: SATA 6 Gbps Interface, compatible with SATA 3 Gbps & 1.5 Gbps interfaces. Unless the drive clearly states it within its spec sheet it won’t work reliably in your system. Using it within a SATA III (6.0 Gb/s) RAID box won’t help as it won’t have the needed sensing logic.

So trying to push your system beyond 3.0 Gb/s is just not possible. As long as the drive is able to saturate the 3.0 Gb/s link and not exceed it.

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Thanks Dan. Yeah, I replaced the internal boot disk with an SSD the last time the spinning disk failed. That helped a ton (> 10 min boot + multi-minute app launch times reduced to normal). I use the mini mainly as a server - file server, backup server, cloud backup downloader (in case I lose access to accounts), security cameras, and long-running tasks.

I was hoping to move most of my external spinning disks from their USB2 connection to something faster. eSata at 3Gbps would have been a lot better than 480 Mbps USB2, but I am also ideally wanting the disks to show up independently since I have mixed sizes and mixed purposes. RAID 10 would not have been a deal-breaker, but not as ideal.

I do have an external dual RAID1 case that hosts most of the file serving filesystems; it is just the backups and security camera footage that is on old unreliable USB2. It works, it just takes a long time.

Anyway, I think I have pretty much maxed out what this machine can do, though what it can do is seriously impressive.

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Hi @danj ,

Thanks Dan

All the best for 2021

Stay safe

Cheers

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@jayeff - All the best to my friend! Just coming up to midnight! You've already past it!

Hopefully the unnamed will find a small hole to hide in before the end of 2021 !!

Stay safe and well!

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