One of the boards on my favorites list for an Unraid build is the Supermicro X13SAE. (Non-IPMI because I probably won't need that and could save a bit on power consumption.)

 

The board comes with a legacy PCI slot at 5 V, 33 MHz, and 32 bit.

 

Now, there are a couple of PCI 2-port or 4-port SATA controller cards, e.g. something like this – https://www.amazon.com/dp/B07R3YFFR7 – or this one: https://www.amazon.de/-/en/dp/B08GPVPS12/

 

From what I could gather, a 32-bit 33 MHz bus will only give you transfer speeds of either 133 MB/s or 266 MB/s, as found e.g. here: https://community.fs.com/article/pci-vs-pci-x-vs-pci-e-why-choose-pci-e-card.html

 

Question: why the two values? 266 MB/s max would be fine for e.g. a big backup HDD, but is that to be expected? What would be the technical reasons/specs for the lower value of 133 MB/s.

 

Elsewhere I've read that 33 MHz & 32-bit at 5 V yields a maximum of 1 GB/s, comparable to PCIe 3.0 x1, but this wouldn't fit with Supermicro's block diagram, which has a PCIe 1.0 x1 connection (0.250 GB/s) going into a PCIe-to-PCI bridge (see image below).

 

However, even that would still be fine for one HDD, i.e. I would use only one of the ports on a PCI SATA controller card. But if the speed per port would drop to 125 or 133 MB/s, that wouldn't be desirable.

 

So does anyone have more insight? Or even real-world experience with legacy PCI SATA controllers & transfer speeds? Thank you in advance. 🙏

 

 

9 hours ago, eicar said:

What would be the technical reasons/specs for the lower value of 133 MB/s.

These bus were 32bit in 33Mhz, if double clock rate to 66Mhz, then bandwidth double to 266MB/s, if further double bus width to 64bit then will be 533MB/s.

 

9 hours ago, eicar said:

PCIe 1.0 x1 connection

PE1*1 was the name, it probably PCIe 3.0.

 

In PCI 32bit 33Mhz, you will got ~100MB/s throughput.