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January 11

Buses

My main machine has PCIe v2. I'm looking at getting an SSD to remove a bottleneck and my options are SATA or PCIe. As I understand things, PCIe M2 is physically different from plain old PCIe - is that correct? Will modern PCIe SSDs behave properly on an aging version 2 bus? Mboard: ASUS H81M-PLUS, OS: Alma Linux 8.5 (patched today). Martin of Sheffield (talk) 15:50, 11 January 2022 (UTC)[reply]

According to the manual, your board does not have an M.2 slot. The M.2 form factor is indeed different from that used for expansion cards. You can get simple adapters from AliExpress for something like $5-10 and I think a similar price on Amazon. These allow you to connect a PCI express M.2 device to a PCI Express expansion slot but they are generally PCI express x4 cards since M.2 provides 4 lanes. Going by the manual, the only slot this could be connected to would be the PCIe x16 one which may be used by a GPU. It's possible some PCIe x1 adapters exist but the advantages of PCIe 2.0 x1 compared to SATA are fairly reduced so it's unlikely it's worth it.

If you do use the GPU slot, there should be little difference between what you're doing and a board with a native M.2 slot. It's possible some adapters are crap and will limit the speeds achieved but this is only likely to be a problem with 4.0 or maybe 3.0. 2.0 (x4) will mean some devices won't be able to achieve their maximum speed, although under certain performance benchmarks will still be a lot faster than SATA. (However assuming you're not planning to use the device in some future computer, this should affect your buying decision. E.g. given current prices, it makes no sense IMO to get a 4.0 device for your system. However within 3.0 devices it's more complicated, since something like a 970 Plus has advantages over most slower devices besides the simple raw sequential speeds.

An additional consideration is that if your board lacks an M.2 slot, it's fairly unlikely the EFI has NVMe so you won't be able to natively boot from the PCI express device. Although it's possible to add the NVMe module to most EFIs without that much work, and I've done it myself, this probably isn't something for the faint of heart. (CrashFree BIOS 3 should reduce the risks a bit, still not with zero risk.) An alternative is you can use something like Clover or DUET on some other device like a cheap USB stick and use that to boot your NVMe device, again I've done it myself and it's generally not that hard assuming you use EFI boot for everything, and if you use one of those small USB devices which don't stick out much it's not that bad, still maybe a bit annoying.

Frankly given that the advantages of a PCIexpress device over SATA are often not so noticable in the real world, I'd recommend you just stick with a DRAM cache TLC SATA device like the MX500 or 870 EVO (not QVO!) [1] although really any SSD will be significantly better than a HD. P.S. Note that M.2 also provides SATA so some M.2 devices are SATA. I see no reason why you'd use an M.2 SATA device in your system, or frankly any desktop unless it's cheaper than an equivalent 2.5" SATA.

Nil Einne (talk) 16:40, 11 January 2022 (UTC)[reply]

Thanks for that. I only have a couple of expansion slots used, both can sit on thew x1 slots. I currently use the on-board graphics, though might in the future want to upgrade to a graphics CPU simply to get more display real estate. It sounds like the SATA route is the one to go down, I've got one SATA free at the moment, I'll ensure the SDD is on the 6Gb/s socket and shift a HDD to the 3Gb/s. I also don't want to go down the rabbit hole of USB or CD/DVD boots to disk. Martin of Sheffield (talk) 17:23, 11 January 2022 (UTC)[reply]