The Raspberry Pi Becomes a SCSI Device

SCSI devices were found in hundreds of different models of computers from the 80s, from SUN boxes to cute little Macs. These hard drives and CDROMs are slowly dying, and with that goes an entire generation of technology down the drain. Currently, the best method of preserving these computers with SCSI drives is the SCSI2SD device designed by [Michael McMaster]. While this device does exactly what it says it’ll do — turn an SD card into a drive on a SCSI chain — it’s fairly expensive at $70.

[GIMONS] has a better, cheaper solution. It’s a SCSI device emulator for the Raspberry Pi. It turns a Raspberry Pi into a SCSI hard drive, magneto-optical drive, CDROM, or an Ethernet adapter using only some glue logic and a bit of code.

As far as the hardware goes, this is a pretty simple build. The 40-pin GPIO connector on the Pi is attached to the 50-pin SCSI connector through a few 74LS641 transceivers with a few resistor packs for pullups and pulldowns. The software allows for virtual disk devices – either a hard drive, magneto-optical drive, or a CDROM – to be presented from the Raspberry Pi. There’s also the option of putting Ethernet on the SCSI chain, a helpful addition since Ethernet to SCSI conversion devices are usually rare and expensive.

Officially, [GIMONS] built this SCSI hard drive emulator for the x68000 computer, developed by Sharp in the late 80s. While these are popular machines for retrocomputing aficionados in Japan, they’re exceptionally rare elsewhere — although [Dave Jones] got his mitts on one for a teardown. SCSI was extraordinarily popular for computers from the 70s through the 90s, though, and since SCSI was a standard this build should work with all of them.

If your retrocomputer doesn’t need a SCSI drive, and you’re feeling left out of the drive-emulation club, the good news is there’s a Raspberry Pi solution for that, too: this Hackaday Prize entry turns a Pi into an IDE hard drive.

Thanks [Gokhan] for the tip!

The Tiny SCSI Emulator

For fans of vintage computers of the 80s and 90s, SCSI can be a real thorn in the side. The stock of functioning hard drives is dwindling, and mysterious termination issues are sure to have you cursing the SCSI voodoo before long. Over the years, this has led to various projects that aim to create new SCSI hardware to fill in where the original equipment is too broken to use, or too rare to find.

[David Kuder]’s tiny SCSI emulator is designed for just this purpose. [David] has combined a Teensy 3.5 with a NCR5380 SCSI interface chip to build his device. With a 120MHz clock and 192K of RAM, the Teensy provides plenty of horsepower to keep up with the SCSI signals, and its DMA features don’t hurt either.

Now, many earlier SCSI emulation or conversion projects have purely focused on storage – such as the SCSI2SD, which emulates a SCSI hard drive using a microSD card for storage. [David]’s pulled that off, maxing out the NCR5380’s throughput with plenty to spare on the SD card end of things. Future work looks to gain more speed through a SCSI controller upgrade.

But that’s not all SCSI’s good for. Back in the wild times that were the 80s, many computers, and particularly the early Macintosh line, were short on expansion options. This led to the development of SCSI Ethernet adapters, which [David] is also trying to emulate by adding a W5100 Ethernet shield to his project. So far the Cabletron EA412 driver [David] is using is causing the Macintosh SE test system to crash after initial setup, but debugging continues.

It’s always great to see projects that aim to keep vintage hardware alive — like this mass repair of six Commodore 64s.

Cloning a Board from Pictures on the Internet

[Andrew] was a pretty cool guy in the early 90s with an awesome keyboard synth that did wavetable synthesis, sampling, a sequencer, and an effects processor. This was a strange era for storage; a reasonable amount of Flash memory was unheard of, and floppy disks ruled the land. [Andrew]’s synth, though, had the option to connect SCSI drives. Like all optional add ons for high-end equipment, the current price for the Ensoniq SCSI card is astronomical and [Andrew] figured he could build one of these cards himself.

Poking around eBay, [Andrew] found the card in question – just a few passives, some connectors, a voltage regulator, and an odd chip from AMD. This chip was a 33C93A, a SCSI controller, and a trip down the Chinese vendor rabbit hole netted him one for $7. Can’t do better than that.

With the datasheet for the chip in hand and a few reasonable assumptions on how the circuit worked, [Andrew] tried to figure draw the schematic. After doing that, he found another hobbyist that had attempted the same project a few years earlier. All the nets were identical, and all that was left to do was sending a board off to the fab.

A quick trip to Front Panel Express got [Andrew] a mounting bracket for the card, and after plugging it in to the synth revealed a new option – SCSI. It worked, and with an ancient SCSI CD-ROM drive, he had boatloads of offline storage for his synth. Great work, and something we’d love to see more of.


8-Track Tapes As A Storage Medium


Before [Woz] created the elegant Disk II interface for the Apple II, and before Commodore brute-forced the creation of the C64 5 1/4″ drive, just about every home computer used cassette tapes for storage. Cassette tapes, mind you, not 8-track tapes. [Alec] thought this was a gross oversight of late 1970s engineers, so he built a 8-track tape drive.

This actually isn’t the first instance of using 8-tracks to store data on a computer. The Compucolor 8001 had a dual external 8-track drive, and the Exidy Sorcerer had a tape drive built in to the ‘the keyboard is the computer’ form factor. It should be noted that nearly no one has heard about these two computers – the Compucolor sold about 25 units, for example – so we’ll just let that be a testament to the success of 8-track tape drives.

[Alec] installed an 8-track drive inside an old external SCSI hard drive enclosure. Inside is an Arduino that controls the track select, tape insertion and end of tape signals. Data is encoded with DTMF with an FSK encoding, just like the proper cassette data tapes of the early days.

On the computer side of things, [Alec] is using a simple UNIX-style, pipe-based I/O. By encoding four bits on each track, he’s able to put an entire byte on two stereo tracks. The read/write speed is terribly slow – from the video after the break, we’re assuming [Alec] is running his tape drive right around 100 bits/second – much slower than actually typing in data. This is probably a problem with the 40-year-old 8-track tape he’s using, but as a proof of concept it’s not too bad.

Continue reading “8-Track Tapes As A Storage Medium”

Hacking old server hardware for new home use

[Arnuschky] was looking for a network storage solution that included redundancy. He could have gone with a new NAS box, but didn’t want to shell out full price. Instead, he picked up a Dell PowerEdge 2800 and hacked it for SATA drives and quiet operation.

It’s not surprising that this hardware can be had second-hand at a low price. The backplane for it requires SCSI drives, and it’s cheaper to upgrade to new server hardware than it is to keep replacing those drives. This didn’t help out [Arnuschky’s] any, so he started out by removing the SCSI connectors. While he was at it, he soldered wires to the HDD activity light pads on the PCB. These will be connected to the RAID controller for status indication. The image above shows the server with eight SATA drives installed (but no backplane); note that all of the power connectors in each column are chained together for a total of two drive power connectors. He then applied glue to each of these connectors, then screwed the backplane in place until the glue dried. Now the device has swappable SATA drives!

His server conversion spans several posts. The link at the top is a round-up so make sure you click through to see how he did the fan speed hack in addition to the SATA conversion.

If your tolerances don’t allow you to glue the connectors like this, check out this other hack that uses shims for spacing.

Adding a Compact Flash reader to a Korg Triton

[Roberto Barrios] has a Korg Triton sampling keyboard which he enjoys very much, but has grown tired of using media of yesteryear to store his work. He had the option of floppy disk or Jazz drive and for a time he was using a floppy-to-USB emulator, but the keyboard still insisted on a 1.44 Mb storage limit using that method. He decided to crack open the case and add his own CF reader.

It should be noted that this hack could have been avoided by using the 25-pin connector on the back of the keyboard. He didn’t want to have external hardware, which is understandable if you’re gigging–it’s just more equipment to keep track of. His solution uses the floppy disk drive opening to mount the card reader. His electrical connections are made with a ribbon cable. He cut off one end, and soldered the individual wires to the contacts on the motherboard. The reader is seen as a SCSI drive by the Korg firmware thanks to a SCSI-to-IDE adapter, so the storage limitation is based quite fittingly on the size of the CF card used.

Look at that cable management. You’d think it came straight from the factory like this!

Making SATA drives work with a SCSI backplane

The problem of persistent and reliable storage plagues us all. There are a myriad of solutions, some more expensive than others, but a dedicated and redundant network attached storage solution is hands down the best choice for all problems except natural disaster (ie: fire, flood, locusts) and physical theft. That being said, the issue of price-tag rears its ugly head if you try to traverse this route.

[Phil’s] had his mind stuck on a very large NAS solution for the last ten years and finally found an economical option. He picked up a powerful motherboard being sold as surplus and a server enclosure that would play nicely with it. It came with a backplane for multiple hard drives that utilized SCSI connections. The cost and availability of these drives can’t compare to the SATA drives that are on the market. Realizing this, [Phil] completely reworked the backplane to make SATA connections possible. It’s an intense amount of work, but there’s also an intense amount of documentation of the process (thank you!). If doing this again his number one tip would be to buy a rework station to make it easier to depopulate the connectors and extraneous parts from the PCB. Since he needs to keep using the board, the old blow-torch trick is out of the question.