I named my dog SCSI. It's always fun to watch the increasingly distant stares of strangers as I explain how to pronounce "SCSI" and what it means.

Atari's Serial I/O (SIO) bus was the USB of the '80s. It is credited as the basis of USB, allowing multiple peripherals to be accessed via a plug-and-play serial bus.

That was a lot of mindblows. From the origin of tar over where /dev/sda came from to the fact, that USB Mass Storage uses SCSI commands 🤯

7:33 There actually is somewhat of a "standard" internal USB connection. It's the header on the motherboard that front panel USB is connected to. There are actually two, one for USB 2, and a different one for USB 3.

I was wondering why Adaptec cards were so robust. They invented the damn thing!

I grew up with SCSI as I worked on Mainframes out of High School. SCSI was amazing compared to ATA, being able to have 16+ devices on a single chain was always amazing. It still gives me a little bit of glee working with SAS devices and saying the name Serial Attached SCSI out loud. SCSI still lives with us.

I love your enthusiastic narration. I had a lot of dealings with SCSI back in the day. It was a running joke in the sysadmin community that, as well as selecting the right ID and ensuring the correct termination, you also had to perform the correct ritual sacrifice of chickens/goats/etc to appease the SCSI gods and get your devices to work properly. In my first job looking after unix workstations I had to deal with about 5 different versions of the standard all in use concurrently. Most of them could be made to talk to each other but if LVD was involved all bets were off (maybe we just didn't have the right adapter...) One small correction: it's SyQuest (pronounced like the psy in psychology) not SysQuest.

Here's the one that will surprise you. The Yamaha PMD1 console used SCSI to interface their DSP angine, console and audio interfaces to each other. The longest SCSI cables were 100 meters long, to connect from.stage to other devices at front of house. There you go. I had learned about SCSI with my Amigas so was surprised to see SCSI with the consoles.

IDE (or, more accurately, ATA) originally wasn't anything remotely like a competitor to SCSI. ATA literally means "AT Attachment", with AT referring to the IBM PC/AT of course. In its original incarnation it was little more than just a way to plug hard drives into the ISA bus almost directly. A far cry from SCSI which was intended as a cross-platform standard from the beginning - so they were very different beasts, even putting performance aside. ATA only became cross-platform many years later, around the mid-90s.

Excellent detailed overview. One minor additional detail - for multi-initiator systems, the SCSI ID was used to indicate which device should be prioritised during the arbitration phase of a SCSI transaction. That's why there are only 8 IDs on an 8-bit bus - each device asserted the bit corresponding to its ID, allowing multiple devices to be uniquely detected.

In my first job, I designed SCSI peripherals (mainly tape streamers though blocked tape devices too) at a small British company. I then went on to become a Field Applications Engineer for SCSI devices looking after the Symbios Logic (ex NCR) range of chips and RAID controllers. I still smile when I see how USB, SATA and other interfaces have taken the SCSI command set and use that in their interfaces. The box at 6:30 looks very much like one of the ones we used for our products, including a parallel port to SCSI tape interface. There are some interesting points about SCSI which you didn't pick up in the video. Initiators were often left at ID7 because that was the highest priority ID (7 -> 0 then 15 -> 8). Better than that, when you mixed wide (16 bit) and narrow (8 bit) devices on the same bus, they could all still talk because they could all see ID7 and then would negotiate the width of communication. This made it great for customers who didn't have to go out and buy all new kit when they changed bus sizes. Also, related to the DMA aspect, is that once the initiator selected the target, it was the target that ran the show by choosing what was going to happen and when. Your computer would say "I want blocks 100-105" but the hard drive would be responsible for fetching the data, and then calling back the computer, for the transfer. Assuming that the computer was boss was an all-too-common fault in software driver design for SCSI devices, though it did get me a few all-expenses paid trips to nice locations fixing the problems 🙂

Another feature that SCSI had before IDE/SATA was command queing. This allowed the drive to optimize access to the disk. A big feature of SAS was the expanders, which allowed networks of drives to be attached (somewhat similar to FC). Your video was very interesting to me as I worked as a firmware engineer for enterprise disk drives and saw the transitions from SCSI-1 to SAS.

Having worked a bit with SCSI for about 25 years, I expected this to be just a nice nostalgic trip down memory lane (which it is). But I was completely unaware of Ultra640. And SCSI printers. And I learned of Adaptec's fate literally yesterday, while researching RAID options for a budget build-your-own server. Fantastic video, thanks! (Oh yeah, had a nice chuckle at the fudge.) I would only add that from about the mid-to-late 90s on, SCSI hard drives themselves were higher-performance than EIDE, separate from the interface. Just because SCSI drives were already chosen for performance, they had 7200 RPM spindle speeds when EIDE had 5400; then SCSI had 10,000 RPM and EIDE/SATA 7200, then 15,000 RPM for higher-performance SCSI (or was 15k after SAS took over?) SCSI hard drives also had 5-year warranties, compared to 3-year for IDE.

Another feature of SCSI was Native Command Queueing which greatly improved performance by allowing out of sequence I/O. SATA drives can now do that as well. SCSI drives also had higher spin speed that IDE - not because of the technology, but because they were higher priced enterprise drives and those drives were usually SCSI. While PC users thought 7200rpm was fast, at work we only dealt with 10k and 15k drives.

USB was inspired a lot by Atari's SIO (Serial Input/Output) from 1978. The video also reminds me of HP-IB (Hewlett-Packard Interface Bus), a late 1960's parallel bus allowing daisy-chaining, later standardized as the IEEE-488 GPIB (General Purpose Interface Bus). It was used for floppy and hard disks (e.g. by the Commodore PET and the HP-85), but mostly for lab equipment (oscilloscopes, logic analyzers, programmable power sources, digital multimeters...)

As a Mac user from 1985 I got real good at building SCSI chains, sometimes one needed to get pretty creative; between devices with 2 DB or Centronic connectors (or occasionally one of each), the odd device with only one connector, and varying ways to set the SCSI ID and whether the chain needed to be terminated made for an interesting time. I had so many cables, with either type of connector or one of each again, it got pretty confusing unless you understood the craziness.

I've been using my home server nas thing with a sas hba as well as a striped pair of nvme because of zfs. I'm quite impressed that all of this technology is able to talk to ancient crap still, like a floppy drive I have in the same server. This is mainly because it's also my ingest machine for literally any generation of tech, and I have retro and new machines hooked up simultaneously. I'm glad this work was done so I can play with stuff that has no right being together.

I remember my Computer Studies teacher teaching us about SCSI. At the time I was still 14 years old and had IDE disks and ATAPI equipped optical drives in my computer. Later on I got SATA based machines. I suspect that all these still use the SCSI command set since the linux kernel implements most IO as part of the scsi driver coupled with ata drivers (for ide/sata)

We got our first home computer in the 80's. It was a 286-16 with a 80 MB SCSI drive. Still remember our neighbor could not fathom how the computer could access the hard drive without a specified hard drive in BIOS, as you usually would do with IDE drives, and they'd show up in the system summary.

We had a SCSI laser printer on our Mac IIcx when I was growing up. Printing was the only thing besides a hard lockup that could stop the cursor moving; normally cursor movement is such a high priority on old Macs it would always work smoothly no matter how busy the CPU was.

There definitely is an internal USB standard, it's used for headers on motherboards which are usually used to pass through to front panel connectors but there is no reason they couldn't attach actual devices. In fact, in some cases they are used for that; some servers use internal USB drives as boot devices that plug directly into motherboard headers.

The interesting connection between the Atari ST and SCSI is that the ST has a "SCSI light" called ACSI (Atari Computer System Interface) or DMA. It was inspired by the SASI bus interface, but with less signals and a slightly modified protocol. Both to reduce the pin count on the connector and the command overhead. The ability to change the bus master was removed and the first command byte also contains the device address beside the command (3 bit device address 5 bit command). But because both busses where so similar, a bridge made from discrete logic could be designed. Atari itself made a reference design for that later on. A result of that was that the ST was one of the few computer systems who implemented their own custom SCSI hardware. (TT and Falcon used Adaptec chips) Sadly there was an oversight in the design of the DMA Chip that dives the ACSI bus. When the Byte transmit counter reaches zero the chip didn't stop sending or receiving data. The slave device has to initiate an interrupt so that the software on the ST can stop the DMA transfer. An Interrupt from the DMA Chip itself would have made the hardware implementation of the slave devices much easier.

When I started building systems back in the 80's, SCSI was all we used. Mostly because of the ease of having multiple devices without having to worry about drivers and incompatibility issues, and there were plenty. Just plugged stuff in and it worked, all the time. Thanks for the memories.

I had a SCSI scanner for years, which was what had me keeping SCSI around.

I remember having a HP Scanner and Printer combo connected with SCSI as part of my first computer set. Really brings back memories.

Literally 1 min in and had to comment. "A time completely different to ours." Priceless. I literally slapped my knee as I laughed.

Usb has an inside the machine standard. USB1/2 is mostly just pins, but 3.0 has the blue plastic connector and thunderbolt has its own funky connector.

I used a Yamaha sampler which relied on SCSI for it's peripherals, well after the time the IDE standard became popular. I resented every over-priced hard drive I plugged into that machine, and don't get me started on how expensive the CD-ROM was. 😨

I remember “SCUZZY” being a Dilbert joke 😂 I had a SCSI internal CDRW drive on the basis that IDE was still deemed to be a bit flaky at the time - I had an Adaptec 2940 PCI SCSI card that an acquaintance in IT gave me - I don’t think it would have been financially viable otherwise 😮

Amazing video! I remember accidentally buying a SCSI Zip drive on accident for a big chunk of change and not being able to use it for six months when I could afford a controller.

The USB 3.0 (USB 3.1 Gen1) specification added UASP (USB Attached Storage Protocol) for large mass storage devices like external HDDs and drive arrays. This uses the SCSI command set instead of Bulk Object Transfer (BOT).

Thanks for the memories. I spent 20 years of my career in storage connectivity. I left 5 years ago to get into cloudy containerised stuff. Great memories of parallel SCSI and the early days of Fibre Channel. You mentioned the standardisation of SCSI, the T10 and T11 standards docs were my bible. However the problem with standards was the interpretation especially with optional features and then there was IBM who just seemed to do their own thing. I used protocol analysers on both FC and parallel SCSI to work with vendors to overcome interop issues. Average interesting time. You also raised multi-initiator SCSI, this was very tricky to get right. Often used in highly available clusters. You are absolutely right that locking was key, much helped by the persistent reserve SCSI command.

I always find it fun to learn about tech that was obsolete before I was born. Edit: we do kinda have a standard for USB inside a PC but it is mostly used to just connect to the front panel.

That was wonderful - brought back a lot of (rusty) memories. Great overview! As for odd SCSI devices, we designed a medical ultrasound scanner (16 bit wide) for it...

Takes me back to my time in publishing the 90s. SCSI, SyQuest Drives, Macintosh G3s, Quark XPress and motorbike couriers

I'd really enjoy a video about fiber channel. It was something that existed on my university servers, but I never understood. Thanks for the video about SCSI. I had a lot of SCSI drives over the years, and now NVMe seems like magic to me.

Starting my Saturday with a fascinating video about SCSI - you just made my day! #InstantLike

16:00 Fun fact Tape Drives are still used in modern times to Store comically large amounts data because they're high density and low cost. The Highest Capacity Tape Drive has a Native capacity of 18TB and can store 45tb of compressed data. These are usually used for long term Archives and Infrequently accessed data because they're excruciatingly slow.

I worked for Columbia Data Products, one of the first companies to clone the IBM PC. After selling of their computer branch we focused on SCSI device drivers and SW sold via Western Digital and designed some custom cards of our own. I used to get advanced versions of every new SCSI device to test my SW on -- so had the largest drives manufactured including Magneto Optics. So all of this is like home to me. We were also founding members on the ANSI X3T9. 2 Committee (SCSI standards) along with IBM & MS. One thing that is interesting is that the SCSI bus & protocols also evolved into the CAN standards for automobiles and are still used today in car computers. The specs are virtually identical. Plus we used SCSI for many NASA projects including the ISS & satellite data storage. I really enjoyed my time with SCSI and what it has become and am proud to have been a leading contributor to the tech. Even today I'm still trying to establish similar standard with other (new) computer hardware. I really enjoyed you video. Reminds me when i was in the center of the computer universe.

For someone who didn't grow up in this generation, THIS IS AWESOME TO LISTEN TO

Fantastic video, love the pacing and structure of these!

One small note, modern IDE and SCSI hard drives do not use SCSI commands, it's only the optical disc drives that do. The reason why device names for them in Linux are sda, sdb, etc is because there is a translation layer (libATA) in the kernel.

Oh the days, I remember installing SCO Unix from tape. I miss the days of the Unix workstation for the power user. The other SCSI use was in the NLE workstation. Back in that day we needed a 10k RPM SCSI drive for video capture. Remember the 4.3 GB Western Digital Raptor drives?

My original pet peeves with USB all the way up to USB2 was yes technically the bus transfer was "fast", but often its implementation at the OS level was absolutely dogshit slow and useless for file transfer where speed was a factor compared with SCSI at the time. SCSI also didn't load up the CPU in the same way as USB where CPU-intensive applications needed every clock cycle they could get. USB had a lot of catching up to do, even in the home market. HUGE improvement over serial and parallel ports at home but that was about it and all I cared about USB for a long time.

At university I named my 1st hamster Scsi, late after university my second hamster was called Fast Scsi and my third hamster was called Fast Wide Scsi. When Fast Wide Scsi had babies they were called lba1 and lun1 and lun2

I've said it before, I love that this channel goes into retro tech that's not just home computers. Having messed with SCSI in most of its forms, I never knew there was an Ultra 640, I thought it pretty much ended at Ultra 320 before going to SAS. Thank you

Still use SCSI in the form of iSCSI for a VMWare cluster of 32 blade servers talking to a storage server at 25Gbps. It really is crazy how after all these years, we are still using SCSI.

Yay! SASI gets some love. I have a SASI controller in an old Cifer 1887 CP/M computer from 1983(ish). A Xebec 1410 with a Winchester 21Mb hard disk that howls like a banshee when it spins up. 😁

In the early 90s my school had a setup where we had SCSI hard drives shared between groups or 4 or 5 Acorns. The SCSI cable would run from one machine to the next. The hard drives would often fall over when we all drived to access the drive.

Thanks for making these video's love the history of old tech, please keep em comming!

Excellent video. Yours is getting to be one of my favorite computing channels on YT :)

Great video! My first experience with SCSI was with a SCSI Zip drive in my 486 PC when the very first Zip drives launched. Why not the much more common parallel version? I had pre-ordered my Zip drive through CDW and they had a package deal for the SCSI version with a 16 bit ISA SCSI card included for only $25 more than the bare parallel drive. Plus the SCSI Zip drive was 20-50% faster than the parallel version to boot. Currently I have a HPE server in the next room humming away with a SAS RAID controller and 8 SAS HDD's in it with provisions to easily add 16 more drives externally if needed. I'm sort of glad the video didn't go too much into SAS since that by itself would have easily added 5-10+ minutes of length with the different versions of SAS and things like SAS Expanders, multipath I/O and so on.

The USB internal connectors are different to the external ones. They're just not used to connect anything internally, but typically only from front case USB or similar stuff.

SCSI itself was a wonderful standard. The issue was to make it work you had to buy expensive cables and really expensive SCSI controllers. I had a 2x CD ROM burner that I had to buy a "bus master" SCSI controller that cost almost as much as the CD burner itself!

Still have a SCSI CD-ROM drive that doubles as a portable CD player that my old dad uses when chilling in the back garden in summer. This video does answer one of the mysteries of the universe, that is why I always had to plug that drive in last and set it to device 7. It was self terminating.

Surprised that you didn’t include Apple computer. It is where I got my introduction to SCSI. It starting point for me at work, we had devices with SCSI and I needed to read up on it fast.

Another fantastic video - I'm not sure if I missed it but I don't believe you mentioned that SCSI hard drives spun up to 10k and 15k rpm vs 5.6k and 7.2k rpm, improving access times and through put.

@7:31 untrue, we have internal USB headers that can power stuff like Bluetooth chips on Wi-Fi cards, fan controllers, things like that :)

What a great and informative presentation! Thank you!!!

I have only used linux for a timy bit so when you said that we may realized while using linux.. I was like “Nah, I didn’t used it enough for sure” and then I see /dev/sdc or /dev/sda and I was like “What the fudge? That’s how far back it goes?” Thank you for this video, it was a pleasure to learn a little more history of pre USB era :))

During my us navy days as a submarine sonar tech, in the early 2000s we were transitioning from legacy bsy1 and q5 hardware to q10 arci (cots) hardware and everything HD related was scsi, for the servers and the raids etc. Everything ran on modified custom versions of Linux (various distros) It started to change in my final years around 2015 to other standards, fun video brought back some memories 😂

What a walk through memory lane. Thank you!

Thanks for the flashback, I remember when SCSI was first adopted, was huge back then...once it was widely adopted that is.

The best bit about SCSI is the way you can have two controllers accessing the disks on the chain. Was handy to have an Amiga and a sampler both connected to the same disks, at the same time.

*Well actually* USB does have an internal standard, often called the usb header on motherboards :) It's actually just like what was going on with SCSI

Still have my working Mac Plus sitting here. I originally only had the Apple 20Mb HD that interfaced through the external floppy connector. When I got my first SCSI 100Mb HD and plugged it into the SCSI-1 port, my computer was transformed. It felt like when today you replace your laptop's HDD with a SSD. Also, loved the views of all the antique U.K. tech. It's not often in the 21st century that you get to see any technology with a "Made in England, Scotland, (or U.S.A., for that matter)" label. It makes me nostalgic for the days when cutting-edge technology made one think of words like Bletchley Park, Turing, and Colossus.

The original Atari ST used ACSI, a sort of cheapo SCSI cousin. In 1991 the Mega STe came with an internal SCSI hard drive (with a small adapter board plugged internally to ACSI, if I remember correctly it might actually been an Adaptec). The (originally intended as a UNIX workstation) Atari TT had both ACSI for backwards compatibility with peripherals and proper SCSI with a 25pin connector. The final Atari computer, Falcon030, had an external micro 50pin SCSI port (intended for external SCSI drives for direct to disk recording due to DMA benefits) and an internal IDE port typically used for a system disk.

Sigh, quest

I absolutely loved hearing about the datacentre applications of this, as someone getting in to IT as a career, please drop more of this precious knowledge!

Just got suggested this vid and channel. Nice content. I look forward to checking your library out. Thanks!

IDE never adopted SCSI command set. It's partially true for ATAPI protocol but that is specific to removable media (CD/DVD, Zip, tape etc) - SCSI commands are tunneled over IDE/ATA. However normal hard drives have always used ATA command set, even to this day as SATA. On Linux side, there is a kernel translator that translates SCSI frontend commands to backend IDE/ATA commands. They're handled the same for the Linux kernel but backend drive command sets are still totally different.

Thanks for an awesome trip down memory lane!

Had an early Pinnacle External SCSI 4x4 CD Recorder, it was daisy chained with a Mirotek Scanmake III SCSI Scanner and SCSI Hdds in the same Adaptec 2940uw controller. Brilliant Class you gave! Thanks!

As a Datacenter guy, I appreciated you even bothering to explain FC at all. GG on the vid

Great memories! My first PC was an Epson Equity II+ (80286-12MHz) with 256k VGA and a 40MB SCSI HDD. The first CD-R I ever burnt was done on a Pinnacle SCSI CD-R around 1995 (Smart & Friendly media) and IT IS STILL READABLE in 2023.

Nice stuff! Brings back stuff I totally forgot.

Thanks for this trip down memory lane. I loved my external ultrawide scsi sun hdd box and external cd burner. Ohh good times

My favorite bit about SCSI was how, back in the 90s, the driver situation was a total mess, and it was so imporrtant to the graphic design industry, because of its support for CDROM and scanners, that Corel took it upon themselves to write a commercial package of SCSI drivers simply because their customers needed it.

Thank you for the comprehensive breakdown of the evolution of the SCSI standard. This goes a long way to explain why some of us considered that sacrificing a goat to the SCSI bus could be beneficial to getting a specific SCSI installation working!

what I have learned while watching this video is: all current connecting standards in computing is that they all have been built on a very solid foundation

I had a small Sparc Station IPC like this, running NetBSD. Great little machine,coming with SCSI tape, external hd, cdrom, optical mouse and flat screen.

Love these videos, I learn a lot

Back in 1999 I built a workstation that had a 3-channel SCSI RAID controller with its own onboard 68020 processor, memory and a real time OS to handle all HD I/O. Each channel was bandwidth saturated with 2 Seagate Cheetah hard drives. My SCSI card also had my Plextor CD R/W drive and a legacy SCSI floppy drive. The 6 Cheetahs were configured in RAID 0 with stripe sizes such that nearly all my file read/writes were distributed over all the HDs concurrently. The real time OS on the card managed the disk IO in a semi intelligent way, doing things like ladder sorting and prefetching into the onboard RAM.

+1 for mentioning Ceph - was a nice trip through memory lane regarding SCSI

I remember changing jumpers around with my scsi devices, thanks to the video brought me some memories. When I was a kid growing up, had scsi Iomega Zip drive, scanner, etc on Mac Quadra 650. Apple has their adb bus used for low speed devices such as mouse, printers and keyboards. It looks similar to the PC PS/2 port.

Excellent video overall; brought back some memories 🙂 Some good, meaty detail is what I like.

Thanks! Always a wonderful ride.

In 1999 the company I worked at had tons of scsi stuff. I acquired 3 avid 9gb external drives along with a physically massive 9gb external micropolis drive. This was a noisy stack that probably rattled my windows, dimmed the lights, and made my external 40x plextor drive skip. It was amazing!

Ah, that warm SCSI feeling... 😁

Thank you for this history in storage lesson.

Amazingly the SCSI protocol is still in use today for various devices like NVME drive interfaces designed for external USB storage drives.

Worked with Sun and Digital Equipment Corp and the SCSI equipment that connected to them for almost 20 years. Terrific working years! For my personal 486, built up on an Adaptec controller, 2 disk drives, QIC-525 drive, and CD Drive. Long live SCSI!

Back in the 2010s, I visited a big old data center and ended up in their lab. All sorts of weird hardware, but what stood out was a SCSI SSD from late 90s, made by some obscure Silicon Valley company. Size of an APC Smart-UPS, packed full with 128 Mb ECC SDRAM sticks and lead-acid batteries. 18.6 Gb size, about 40 lb weight. Unfortunately, it died in 2003, according to the sticker, and was never fixed.

Wow, I happen to be the minority that has Fibre Channel. :) Sun Blade 1000 and 2000 workstations have FC-AL disks and one of those is on my desk. Retro computing is fun indeed. Great video, I actually now have something to show to younger colleagues when trying to explain what is SCSI.

I hope you plan to talk about SCART next, that what my mind ran to when I first heard SCSI

Surprised you didn't cover the rather important advantage of SCSI is that they auto-negotiated transfer speed for each individual attached device. This allowed one to make long chains of devices with different transfer speeds, and a [good] controller will ... just figure it all out. It therefore afforded many choices about upgrade paths, because one had the option to retain an old-but-good device for an indefinite amount of time, until truly superior replacement technology became available.

Another occasional SCSI device in the 1990s was a slide camera. It literally had a photographic camera directed into a sealed compartment with some sort of high resolution image generator. Maybe a hi def CRT, I'm not sure. Could have been lasers. Each photograph would be exposed for some minutes while the image was scanned out. Later the finished film would be developed as 35mm colour slides for use in lectures etc. These were sharp as a tack, the thing was scanning thousands of lines per frame. The one we used had a choice of connections. SCSI was fastest, but there was also GPIB, maybe others.

I worked with SCSI ever since it was first released as a standard and something that has always amazed me is the number of times I've been asked to troubleshoot a system only to find that the SCSI chain either didn't have any termination, termination only on one end or in some cases three terminators. To me it was so simple to understand. The first and last device on the SCSI chain has to be terminated. If a controller has both internal and external SCSI connectors but only one controller then everything is going to connect to one chain. So if there's internal HDD's and a external Scanner the chain has to be terminated on the physically first HDD in the chain and at the Scanner, and the controller cards terminator has to be disabled. This simple thing tripped people up all the time. Just to make it better if the external scanner or CD or whatever was the only device on the chain apart from the controller it would often kind of work without termination at the scanner. So when you got there and told the customer that they needed a terminator at the scanner end they'd often just look weirdly at you. Almost all scanners came with either a terminator you plugged in to the second SCSI port of the scanner, or a passthrough terminator that sat between the SCSI cable and the port on the scanner. But some had internal terminators that you enabled using a DIP switch. Next problem was people not assigning a free SCSI ID and wondering why it didn't work with two or three HDD's using ID0... Something that came late in the SCSI scanner market was scanners with only one SCSI connector. These could not sit at any other position than last in the chain. Weirdly enough some of these didn't have an internal terminator even though by design they were doomed to always be at the end of the chain. As for server use, there were quite early a standard for hot-swappable SCSI drives. The connectors position on the drives was standardized which made it a lot less fristrating than trying to use IDE drives. With IDE every manufacturer had their own idea of where exactly on the drive the IDE controller and power connector were. I worked with storage chassis that had several backplanes you could swap in that allowed you to use IDE drives from different manufacturers be used. But you couldn't use for instance a Conner drive and Seagate, Western Digital or Maxtor drive on the same backplane. The alternative was to have a drive sledge that had an interposer of some kind which adapted the drive I/O to a connector that then mated with the connector on the backplane. But then you had a new non standard connector that could introduce problems. All of this finally got solved with SATA as now the dimensions and exact positioning of the connectors were finally standardized. The controller situation was also interesting. As said SCSI was the grownup solution while IDE was the wannabee kids solution. But there were some who tried to make IDE controllers smarter early on. I remember a IDE controller with cache memory. I think it was 2 megabyte, and it had a battery backup. This was IDE, not EIDE or PATA. I can't say I noticed much of a difference but it was used in a server. No RAID functionality though. Still I think it was an interesting attempt. Now something not mentioned in the video was a big limitation with the parallel IDE, E-ID and P-ATA world. While you could have up to two drives on one IDE controller only one of them could be active at any time. That is even with the fastest and latest standard that supported DMA and so on only one drive was active at a time. Want to read something from one drive and write something to the other drive? Well send the read request to the first drive and wait for the data. Only then could the controller yell at the second drive that it had data to send to it. This meant that copying files between drives on the same controller was a lot slower than if the drives were on different controllers. Motherboards toward the end of the parallel IDE era tended to have two IDE channels which effectively was two separate controllers so choosing where to connect the drives could be important for performance. With SCSI this was never much of a problem. The controller sent commands to the drives whenever the bus was available and didn't have to wait for them to locate the data and read or write it only to tell the controller they were ready. SCSI devices can even send data directly between each other without involving the controller, though this was not often used.

Another excellent stroll down memory lane, many thx 😀👍 You have also reminded me ... whatever happened to Silicon Graphics? Only contractor I employed who didn’t envy our new (at the time) Sun Workstations was one who pined for a Silicon Graphics unit ... but I assumed it was just oneupmanship.

I recently found my box of NeXT Step/Open Step drives and controllers. NeXT required SCSI drives and I believe macos keeps this convention in its code like Linux. In my box is an assortment of cables and terminators, a CDROM drive, various internal and external drives. All things I used to use to keep the NeXT boxes alive. I had a few of those SCSI printers. Massive dye sub printers that took two people to lift. Floor standing scanners and even one high resolution film printer used SCSI. All the high end gear used one type of SCSI or another. One of the problems with SCSI was the cables couldn't be too long so whatever you were using it on had to be next to each other.