Hacker News Reader

Comment by jauntywundrkind | Hacker News Reader

The article goes into that some.

> To put that all another way, VESA came up with a slightly faster bus standard for the next generation of graphics cards, one just fast enough to meet the needs of 486 users. Intel came up with an interface designed to reshape the next decade of computing, one that it would even let its competitors use.

It's crazy how useful PCI was. Intel kept being the company that made standards, that created places for cooperation. In an industry where historically it felt like every company wanted to take on the world solo. Its hard to think of a company that has done more to grow the pot in an industry than Intel.

(Intel also created nvme!)

View on HN

> (Intel also created nvme!)

To be fair they did that because there were already several vendor-specific proprietary PCIe-attached-SSD products (notably in Apple's macbooks) and the lack of a standard way of doing this was a major fragmentation risk.

PCI and PCIe were generous gifts from Intel to the rest of the industry and involved giving away a fair amount of hard-won development results (like the pcie serdes electrical parameters). NVMe was more a case of Intel being the referee because we needed somebody to make an arbitrary decision.

> there were already several vendor-specific proprietary PCIe-attached-SSD products (notably in Apple's macbooks) and the lack of a standard way of doing this was a major fragmentation risk.

Are you confusing the protocol for the mechanical connector and form factor? Prior to using NVMe, Apple was using PCIe SSDs that spoke AHCI, the Intel-supported industry standard for storage controllers used by almost all SATA controllers.

The M.2 card connector and form factor were standardized by PCI-SIG and are unrelated to NVMe.

As I understand it, speaking AHCI doesn't mean the higher level drivers exist in the BIOS to allow booting, so things were a long way from standardisation in those days. You couldn't just put an AHCI drive in an M.2 slot and expect to get on with your day.

A PCIe SSD speaking AHCI means the boot firmware and OS will see it exactly the same way they would see an add-in card providing one SATA port populated with an SSD that is mysteriously faster than a 6Gbps SATA connection should allow. Those PCIe SSDs used AHCI exactly because that's what everything already had drivers for.

It's still grand that NVMe massively improved the world beyond "can it boot". Having 65536 different submission queues, having read/write opa take 1 rather than 6 round trips, and a variety of other improvements.

I think we still would have been stuck with a bunch of vendors making exotic expensive boutique flash storage systems for a while had Intel not come by & made a fairly sizable overhaul of the existing protocols.

FYI, nobody supports 65k queues. The protocol allows it, but the hardware has lower limits. Most SSD controller vendors have had trouble supporting enough queues to assign one per CPU core on high-end systems contemporaneous with the SSDs.

That's the thing, not everything had the drivers. Gigabyte in particular omitted the important bits for a while. I'm not going to claim I'm an expert, but I ended up with a very fast SSD which could only be made bootable by extracting parts of another vendors BIOS and creating a custom UEFI image with them added, and life is far too short for that.

What you're describing sounds like the process for adding NVMe support to a board that shipped with a PCIe M.2 slot but no NVMe driver in the firmware. There were quite a few of those circa Intel's Z97 chipset, and motherboard vendors were inconsistent about when or whether they shipped firmware updates to add NVMe support. A few early NVMe SSDs included a PCI Option ROM to provide NVMe capability on systems that didn't already have it. For any other NVMe SSD, the firmware needed to be modified to add a UEFI DXE driver for NVMe to enable booting.

There were very few consumer PCIe SSDs sold before the adoption of NVMe, and they were almost exclusively sold to OEMs rather than as retail products. A few like the Samsung XP941 and SM951 were available through grey-market retailers for about a year before Samsung launched the 950 PRO as an official retail product, using NVMe (with an Option ROM). (Note: the SM951 existed in both AHCI and NVMe variants, so some of those grey-market retail sales were of drives that were essentially 950 PROs with slightly older flash).

It's not entirely impossible that Gigabyte shipped boards that couldn't boot from AHCI PCIe SSDs. But it would be difficult for that to be a driver issue. I'd expect those boards to also have difficulty booting from an add-in SATA controller card, because the difficulty booting from AHCI SSDs would have to come not from a lack of an AHCI driver but from a misconfiguration preventing that driver from being used with anything other than the SATA controller built-in to the motherboard.

How sure are you that you didn't miss the brief era of AHCI SSDs entirely and are simply remembering early NVMe teething issues?

I am 100% sure. It is indeed an SM951/M2/ACHI[sic, that's what's printed on it], I have it in front of me. It went in the only system I've built in the last 15 years, so there's no room for confusion.

It had to be AHCI because macOS didn't support NVMe in this era, and the motherboard was also chosen for Hackintosh compatibility, but I only ever used it as a data drive because of the boot issues. That was probably the best option for its use as a fast compile machine anyway, but it did become a PITA when I wanted to sell the machine.

I'm afraid I am not familiar with this technology - as I said I am not an expert - so perhaps driver is the wrong word. Perhaps I did end up reading advice relating to the NVMe variant, information was very hard to come by. All a very small historical footnote now anyway!

Reply on news.ycombinator.com