The Return Of SCSI

There was a time when high-performance disk drives used SCSI — the Small Computer System Interface — and everything else was kid stuff. Now, advanced forms of SCSI are still around but there are other high-performing disk interfaces, too. But some old gear really loves their classic SCSI ports, and [Adrian] decided to try hooking some of them up to some modern computers. You can see how he did in the video below.

The key to the attempt is a USB to SCSI adapter which was unusual but not unheard of, and [Adrian] came across one from 1999. Of course, you have to wonder if a modern computer will support the device or will be able to load the drivers from the old CD.

One of the problems with these adapters is that SCSI was a high-performance bus for its day, and the corresponding USB speed was not so much. Parallel SCSI used differential signaling and could reach up to 320 MB/s. Ordinary USB weighs in at 1.5 MB/s. USB 2 did a little better, but it would take USB 3 to eclipse the old SCSI data rate. Of course, SCSI went serial like USB and modern serial-attached SCSI can blow the doors off even the fastest USB devices.

We doubt you really need to use a SCSI device as an everyday thing, but you might want to or need to read one that shows up. Plus it is just a really interesting look into the way things were. Finding the drivers were, as you’d expect, a real pain. Turns out, he probably didn’t need to bother as Windows knows how to treat it as a storage device but he didn’t figure that out right away.

Android didn’t seem to work as well, although that may have been because the phone didn’t recognize the disk format.

67 thoughts on “The Return Of SCSI

    1. I reckon you’re right. If someone is up for a project, all you need to do is translate the lowest level as usb-msc is scsi encapsulated over usb.

      I just can never get my damned head around the scsi standards enough to grok the low level of parallel scsi. I’ve tried, I just can’t get it.

    2. I did get one with my scsi scanner back in the day, it was indeed a cypress fx2usb with custom firmware.
      Driver support had a very short list of windows version handled, so the scsi scanner became quickly a linux scanner only.

      1. If you have a dispensable USB-SCSI adapter, I would buy one. I revived a 1990s Jukebox (with 100 CDs capacity) and I would like to control it from a Raspberry Pi or an ESP32. This USB-SCSI adapter would be a great bridge between the devices.

    3. I can’t speak for all of them but you’re right that the main processor on my Ratoc U2SCX (which works on 64bit windows) isn’t anything special, it’s a Cypress CY7C68013 aka FX2 – probably one of the more common USB to whatever you want chips ever made. The programming for it is stored on a 24LC64 64Kbit memory chip which isnt hard to dump, however it only seems to store a bootloader to get the chip running and the main firmware is loaded via USB from the computer (this firmware is readily available with a google search and is included with the drivers).

      …but it’s far from the only chip, it also has a Qlogic FAS236U SCSI controller chip which does all the heavy lifting. Qlogic was bought out by Marvell and there does theoretically seem to be stock of their replacement chips still available on some slightly shady websites… however I can’t find a datasheet and it might not be identical so YMMV.

      It also has a few other chips providing SCSI termination and the various required voltages however these can probably be replaced pretty easily with a linear regulator or two putting out 2.85v and a couple of 110 ohm resistors.

  1. Ohh. Scsi… Another example of a half implemented protocol. I have worked with it during the last 30 years and it never was a pleasure: all the different connectors, termination systems, bus sizes, single ended, differential and low voltage differential, the always changing amount of jumpers used on a drive. Horrible.
    And never stable. One day everything boots up fine, the next no drive can be found, having to reboot several times to get the system working again.

    They say that if you want a working scsi setup, you have to sacrifice a goat or a kidney to the scsi gods.

    Case in point: I still have a very large scsi Scanner (Agfa XY-15) connected to a Mac G4 Quicksilver. The scanner was working perfectly under both Mac osx 10.2.8 and Mac is 9.2.2.
    After a move in February to a new location, the software cannot find the Scanner under Mac os x and works fine under Mac os 9.
    I’ve changed everything: cables, terminators, scsi cards, Macs, new installed OS, drivers, software. But no dice. And yes, when first installed with Mac os x last year, a smooth ride. No hiccup, no complaining about unable to find the Scanner, just startup and scan. And now it is only working under Mac is 9, with USB 1.0 speed to write data to a thumb drive.

    1. Never had a problem with it, on Amiga or PC. At home or in server rooms.
      In fact had a drive being shared between the Amiga and PC with two bus masters – do able thanks to those “annoying” jumpers you mentioned.
      In fact found it super reliable, more so than IDE at the time.

      maybe the problem was the mac ?
      it normally is.

      1. That would be rather unusual. SCSI was Apple’s “native” mass storage interface (internal and external) for decades, and with good reason. It was (compared to the alternatives at the time) reliable, fast, and flexible.

        But SCSI could be “bitchy”, especially with seemingly small things like e.g. the correct termination. My personal nightmare were SCSI cards for the AT-Bus of the PCs of the time. And, speaking of Macs, of course the Mac IIfx with its “black terminator”.

        1. That terminator was a beitch to find ,I always lost mine. Hey I didn’t know Arny come in a different flavour lol.” I’ll be back.” To give trouble if you don’t install it.

      2. Same here. Neither my A1200 nor my AmigaOne have had problems with SCSI devices over almost 30 years of using them (20 years for the A1). In my A1200 I have still connected an Epson scanner, two optical drives, 3 HHDs, ZIP, JAZ (alternated with the scanner, SCSI chain only allows 7 devices plus host, hehehe). Quality cables and proper termination always help.



    2. I’ve connected lots of things with SCSI.

      At the peak, I think I had 3 IBM 9ES hard drives, two internal Plextor optical drives, an external Nakamichi CD changer, and an HP flatbed scanner.

      It was a completely bizarre mix of wide, narrow, fast, slow, and ultra.

      It worked fine. I used that rig reliably for years, until neither CD-ROMs nor 9-gigabyte hard drives were useful anymore.

      I still have both kidneys.

    3. I find the complaints about SCSI humorous. Setting up SCSI was easier than trying to put together some computers back in the day with a motherboard that really didn’t have anything on it (other than the CPU, card slots and usually the memory) and you had to add a video card, sound card, controller card and whatever else, then set all the jumpers for the IRQs and everything else so there weren’t any conflicts, then set the bios for how many tracks, sectors and cylinders the hard drive had. If your computer lost the hard drive setup and you put in the wrong info the computer wouldn’t read the data on the hard drive. Then there was at least one combination that someone I met had tried to put together and couldn’t get it to work. they finally contacted one of the board manufacturers as were told there was an undocumented memory location being used which made it impossibly to combine with one of the other cards.

      On a side note, Apple didn’t like the fact that their computers used something pronounced “scuzzy” and tried to get everyone to pronounce it “sexy”… they didn’t succeed.

    4. It was not so much “half implemented” as “the best answer for MANY unrelated jobs”, and that flexibility showed in the scope of knowledge it required for proper function in many situations.

      I won’t say I never had any problems with it, but every time I did have a problem, it was due to different pieces of the gear in the project making conflicting assumptions about which subset of scsi was in use.

  2. SCSI isn’t an old outdated thing. Most severs use Serial Attached SCSI (SAS) as there more economical for a performance server.

    SAS drives can respond to SCSI commands, SATA commands (for compatibility) and be configured to inherently support RAID configurations.

    I have an old SAS drives on this PC connected to a standard SATA port. It’s slower on a SATA but that doesn’t matter because the boot drive is SSD and the SAS (as a SATA) is still faster than anything I would be transferring data to or from.

    1. SATA supporst EIDE/PATA commands.
      That still doesn’t make it anything like EIDE/PATA.

      SCSI not being outdated because SAS supports (some?) SCSI commands is like comparing paper to HDDs because both can store characters…

      1. PCI(e) (Peripheral Component Interconnect) standards supports (a subset of) PCMCIA (Personal Computer Memory Card International Association) standards which supports CF (Compact FLASH) standards which support IDE (Integrated Drive Electronics) standards which support SD (Secure Digital) card standards which is how you modern desktop PC interfaces to an SD memory card (except that it buses via USB (Universal Serial Bus) in most cases). The PCI(e) standards also support ATA (Advanced Technology Attachment) which is now called PATA and supports SATA and mSATA and eSATA which support SAS (Serial Attached SCSI (Small Computer System Interface)) which supports native RAID.

        This is all done specifically for compatibility from one level to the next but as a consequence of that it becomes from the first levels to today.

        So in the end a modern standard reads like a complete history of buss and protocol history. Oh bus was buss back in the beginning.

        So the “next” standard will include PCI(e).

        These old standards don’t go away, compatibility with previous standards is written in at the time the standard is created because at that time the old stuff still needs to work. Then there stuck as part of the standard and with the next iteration they are included in an even newer standard.

        And sure you can’t plug a (E)IDE drive which is ATA into a SATA socket but the underlaying protocol is ATA and the CPU has no clue that it’s talking to a SATA and not an (P)ATA (like IDE).

        But you can make an adaptor and though it might have to do a hardware conversion like serial to parallel it wont have to do any protocol conversion. So yes, it’s not that hard to connect your old Seagate ST225 20MB (MFM) 30MB (RLL) to a modern computer as it’s just hardware without protocol conversion.

        Anyway that’s basically how it goes. I might have gotten some of it wrong as I haven’t worked as CME or NME for decades but of course I still use a PC.

        A couple of years ago I was making an IDE interface for a retro computer that was made long before IDE existed. I couldn’t get the damn thing to work. I was researching / referring to the IDE standard. I looked at the PCMCIA standard and realised there were differenced in early IDE (8 – bit). 16 Bit was first just 8 bit read twice (and this was often called 8 bit) and then full 16 bit. I was reading about what you would call half 16 bit rather than the true 8 bit and that is why it didn’t work. Luckily the hardware was based on CPLDs so it was just a rewrite for some HDL.

      2. SaS *uses only* SCSI commands, no more no less; your SATA analogue is quite apt, and that basis on SCSI is the reason SaS is preferable in servers despite the trivial use of SATA drives in SaS backplanes. PCIe similarly embeds PCI, and high-speed 64-bit PCI-X mirrors SCSI’s evolution.

        SATA optical drives on the other hand, still use the ATAPI standard for embedding SCSI commands in ATA for their basic functions. USB attached SCSI is preferred over the classic “mass storage” protocol in USB 3 storage devices.

        When you take away the SCSI command set, parallel SCSI is just an 8/16/32-bit differential printer port.

    2. Interesting bit of trivia: SAS RAID controller hardware exists it many HP “Workstation Class” towers. The Z800, Z820 etc will accept both SATA and SAS drives, simply tell the mobo what you have. (I even found some SAS (New) drives for $10 USD a few months ago) And yes, both formats are “Hot Swap” capable.
      The TRW swap meet here in Los Angeles is a treasure.

      1. To expand on my above post, the HP Z800 series have both SAS and SATA RAID control circuits.
        And yes, that means two different connection buses. To run SAS, you plug the cables into the SAS bus, and if SATA into the SATA bus. Both run well, but SATA seems to have larger capacity drives available. At least, at a price I’m willing to pay.

    3. This isn’t correct, it can’t be correct. SAS DRIVES can operate in SATA mode but SATA controllers cannot operate in SAS mode. If you trials have a SAS drive and it’s working then it’s connected to a SAS controller.

    4. Not all SAS drives work on SATA. Would be nice to know how to tell which ones do because there are some really good deals out there on SAS drives. SATA drives *should* work connected to a SAS controller but I wouldn’t be surprised to find some that don’t.

      1. No SAS drives work on SATA would be more correct from my understanding. They wont even physically connect to a SATA controller. SATA drives however will connect to a SAS backplane. The connectors are designed to prevent plugging a SAS drive into a SATA backplane.

  3. I don’t know of a open project for USB-SCSI, but several other SCSI-device projects exists.

    RaSCSI was covered here a few years ago:
    It emulates SCSI devices using a Raspberry Pi (sorry a 555 won’t do it). project on github:

    There are several other attempts, like:

    Also this blog-series may or may not be of help:

    1. Haven’t looked into rascsi yet

      Running scsi2sd in my old samplers and managed to get a old SCSI card and the samplers software running on windows 7

      Never had dealings with SCSI before that. Wasn’t too painful.

  4. I installed an PCI-X to PCI Card in my modern highspeed Computer and than I tested a Buslogic KT-930, a NCR SC200 and an Adaptec AHA-2940UW.
    For testing purpose I installed a DDS4-Drive.

    The drive was easily detected by my kernel. It was possible to rewind, position and eject tapes. So it worked, but the computer made a restart as soon I try to transport heavy data stream. (read a tape!)

    I think the reason is that the shity PCI-X to PCI Card used a more shity USB-A to USB-A (!) cable to connect PCI-X LVDS-lane to the PCI-bridge on a second PCB. So perhaps it should work with better cable and perhaps some serious LVDS-Driver. But I did not test it.

    Of course in these days there is no reason to connect a SCSI harddisk to a computer, even if you are the proud owner of a fullsize 80GB brick. :-) But there are also DDS-drives, MOD-Drive, CF-Cardreader or my PCMCIA-Card2SCSI Adapter that more interesting.

    SCSI to USB cable are seldom (but I have one). They not a good solution because they try to convert SCSI-hardisk to USB-Drive. Sometimes it works and sometimes not, but it never works with more interesting devices.


    1. I still have a Adaptec AHA-2940UW in a working pc and it has no problem reading old tapes (I’m still finding ones I want to read on my old tanberg drive) and it also has no problem reading my very good negative scanner – and negative scanners peaked many years so no point buying a current one..

      I used scsi hard disks a lot in their day, they were fantastic compared to ide, ran faster, and you could have way more of them running in a box (I once ran 32 of them in a raid system..). They also handled most real life work much better than ide.
      But yes, I wouldn’t run a old scsi disk now!

      1. Currently running a SCSI-1 HDD in my old SGI desktop. I guess I’d feel more comfortable if there was a SCSI-1 to SATA or IDE adapter to allow me to run a newer drive, but last time it was powered up, it booted…:-)

      2. What OS are you running that has drivers for that card? I have an old adaptec scsi card for some drives I have some old data on but there’s no Windows 7 drivers for it.

          1. I think there is a ip over scsi driver is some old versions of linux but latter got removed I wanted to play around with but don’t have as much scsi around as I ised to.

        1. the 2940W runs fine in win 7, and there are win 10 drivers around for it too (I haven’t tried them). For linux you have to go to an older version or much around a bit..

          1. Huh? For Linux you can use the newest version/kernel as you like. You will always find the driver for the oldest SCSI-Card in the kernel. The problem is realy only a stable working PCIe to PCI bridge. But that is not impossible. It was used on many mainboard 10years back and is still used on expensive industrial mainboard. So it is possible. The only problem is the ugly quality of actual chinese implementation of this adapter boards.

  5. As a Unix sysadmin, I used SCSI quite a bit. There were these disk chassis that did RAID on the drives you plugged in and you hooked up your computer via SCSI and saw one drive.

    The chassis was working in SCSI target mode. I always thought it would be cool to have a linux or BSD system that could act as a target but have a number of IDE drives in software RAID.

    Nowadays, iSCSI over 10G ethernet is probably a better idea.

    1. I hope people copy the data before they changed from SCSI to something newer (I did it), but there are still some device that are so cool you will miss them. (for example my 2.6GB MOD) It feels wrong even if you can replace it with one SD-Card today. :-)

  6. The last frontier is speed with writing to external hdd’s.

    I bought several 18TB drives recently so that I can consolidate and copy from my older drives to the newer 18TB drives, have them organized a lot better, and have plenty of space on each one. I do this every few years – buy several bigger drives, copy everything over and the smaller drives remain as backup drives that I box up.

    It took me two weeks to get everything copied over and it is taking me another three weeks to get things moved from one of the 18TB drives to another 18TB drives in order to organize.

    I have two 16TB external drives that I will make a solid backup using backup software of everything to them and I have a feeling that will take another couple of weeks.

    1. The onky scsi drives I have were on Macs. But after I moved to a 586 and Linux, I got for $20 a Mac, I guess a PowerPC model, that had both scsi and ide.

      So I could consolidate a few scsi drives onto an ide drive.

      1. I was kidding, I remember what is on the drive. Back around 1997, I bought some surplus motherboards for my students. All were kitted out with a built in SCSI interface. It seemed to intrigue them.. Sadly, that surplus vendor has vanished, (along with many others) ..

          1. I don’t want one personally. I’ll be going the way of the 5×86 before that long lol.

            There is a whole subculture of retro-computer collectors that would love those parts and pay good money. Go chat on one of their forums.

            And though the earlier days of the IBM PC might not seem so “retro” to some for others it was their youth days.

  7. I used to use ESDI Drives way back when SCSI wasn’t natively supported in early versions of Sco Unix. Later down the Track I kept Using the ESDI Drives on a SCSI Adaptor (2 ESDI Drives to 1 SCSI ID.) Had Huge performance Gains over SCSI-1 (Parallel). Mind you they Weighed a Ton and spinning them up sounded like a Turbine.

  8. I’ve been using scsi since the early 1980’s on PC’s and SASI before that. I’ve been looking for means to address scsi & sas drives on laptops for decades with no luck. Mainly as I need to troubleshoot and work on drives (reformat, change block sizes, modify grown lists of bad blocks, etc). Found a reference for a SAS to ExpressCard adapter but as usual it was proprietary and only ‘supposedly’ worked with windows 98 but when trying that after much effort to get drivers it still wouldn’t work. There’s a real lack for these things and I for one would easily pay $500+ for such a solution especially something that can handle SAS to say thunderbolt to get something ‘relatively’ new and not have to contend with USB interference with direct drive commands.

  9. Interesting. I used SCSI a lot but primarily for scanners. I used to have a Adaptec USB to SCSI adapter that I could never get working on Windows 10 so I might have tossed it :-( But in the interim since I sitll use a Canon slide/negative/APS SCSI film scanner, I bought an Adaptec SCSI card which works sort of and I can use Deskscan to access it. I am nog going to see if did not toss out that USB scanner since if I can find it and get it working on Windows 10/11 I might not need to have SCSI cards in my PC anymore

  10. hi i was doing computer music in the 90’…and my computer was a super computer with two scsi hd…payd something like 3500 euros (actualized)! unfortunately it dosn’t work no longer…i think the modo is gone…can i in your opinion get datas back from my hd?? they are 68 pin scsi lvd/se Seagate… thanks!!!!

  11. Due to the 80286 processor, BIOS and BUS limitations of my first Tandy 3000HL computer in 1987, I quickly assed the ISA Adaptec AHA-1522A host adapter in 1989. Every subsequent iteration of every unit inclued the latest Adaptec SCSI controller, the 2940 added to my highly modified Intel 302, the 39160 and ultimately the 39320 was added to my Intel PB940 tower unit. At my place of employment, I was occasionally referred to as “Mr. SCSI”. Generally it has been a great run and I am currently in the process of adding an LSI 29320 to my DELL XPS-8920. Also am considering an Asus WS X299 SAGE/10G AS based unit with SAS technology.

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