Atari System V UNIX Saga – Part III – SCSI Disk Replacement

(note this is a guest post by Tenox)

In previous posts from ASV series I have explained why I got hooked on Atari System V UNIX and what I had to do to get a decent resolution out of Atari TT. Having built the VGA monitor adapter, the next challenge was to replace the internal SCSI hard disk with a flash storage of some sort. I really don’t like spinning hard disks and especial the old ones.

I have mentioned that there are two surviving ASV disk images. The better one was made out of a rather large old, loud and obnoxious Maxtor. I’m definitely not having this monstrosity inside of my beloved Atari!

Maxtor LXT340SY

Maxtor LXT340SY

 

So how can you replace an old SCSI hard disk with a modern flash device? There actually are several different ways.

If you have the money you can go industrial route, which is a SCSI disk replacement for various machinery and embedded systems produced by ReactiveData. You can buy one of these for a little over $1000 USD. The good part is that they substitute a specific real hard disk model and are exceptionally good in quality of emulation. However, spending a lot of money on my TT and TenoxVGA already, this really wasn’t an option without getting a divorce.

Another approach is to use SCSI to IDE bridge combined with IDE to CF adapter or possibly SCSI to SATA bridge and SATA SSD disk. These are widely used by Atari / Amiga / Mac 68k community. The most popular bridge come from a company called Acard. I actually had one of these at hand, AEC-7220U which I used for TOS/GEM work.

acard front

acard front

 

Did it work? As you can guess – of course it didn’t! The initial boot loader errors out unable to read disk capacity.

Atari SYS V failed to boot

Atari SYS V failed to boot

 

Atari ST/TT, somewhat similarly to 68k Macs require a hard disk driver, present on the hard disk itself. There are several 3rd party implementations, some of them, like HDDRIVER maintained up to present date. Unfortunately these drivers are TOS specific and obviously don’t work with Atari Unix. The system comes with it’s own hard disk driver which seems to be obsolete and with limited hardware support.

The next step was to research and try out some other SCSI to IDE bridges in hope one would just work. And surprisingly there are several to choose from.

The second on the line was I-O Data R-IDSC21-E/R. No longer produced and supported, however still fairly popular. Usually regarded as the ultimate bridge with most fancy options bells and whistles. It has most jumpers and modes of all tested devices. For instance ATA PIO and DMA modes.  Unfortunately this didn’t help at all and same error was observed.

idsc21e

idsc21e

 

Another device tried was Yamaha v769970. This bridge was conceived to allow use IDE CDROM and Hard Disks with Yamaha samplers. No longer produced and obsolete, it’s somewhat most easy to set up, robust and stable. It’s actually my favorite bridge for day to day use, except for ASV where it just doesn’t work.

v769970

v769970

 

More recent kid on the block is an integrated SCSI2IDE + IDE2CF in one device called Aztec Monster. Recently designed and currently produced in Japan (you can buy one on eBay) is a fairly decent choice, which I recommend to every one. I had a lot of luck with these, except for ASV of course…

CF_AM_r1_1

CF_AM_r1_1

 

I also looked in to SCSI to SATA bridges, like this one, but they have additional issues, like need to convert LVD to SE on one end and SATA to IDE to CF on the other. Little bit too complex for what I wanted.

Being out of luck I started researching if it would be possible to build an open source version, which can be easily diagnosed and fixed. Doing so I found out that there in fact is one open source SCSI adapter called SCSI2SD.

SCSI2SD_V3.0_plain

SCSI2SD_V3.0_plain

 

I was bit skeptical in the beginning but then I though that being open source it can be debugged and fixed if it needs to be. So I immediately ordered one.

Once it arrived, I plugged it in, applied the image to the card and BAM! It worked! The system booted fully and worked flawlessly!

Atari Unix System V – Boot Sequence from Antoni Sawicki on Vimeo.

Going back to the hardware, there are some gotchas with SCSI2SD. First of all it’s not really SD card but rather a micro-SD. Which is not a big problem, but requires magnifying glass and tweezers to operate. Secondly even though the board looks like standard 3.5″ width, it in fact it is not! So a warning: it doesn’t fit 3.5″ hard disk slot!

photo 1

photo 1

 

When one side is placed on 3.5″ HDD holes the other leaves a gaping hole. Just doesn’t fit. Apparently you need a special 3D printed bracket to fit it together. Or a double sided tape, I recommend 3M VHB Tape. The upcoming version will feature 2.5″ sized holes, so look for this one.

Other than that SCSI2SD is flawless and it works fantastic. One feature that Mac users will appreciate:

--apple Set the vendor, product ID and revision fields to simulate an
        apple-suppled disk. Provides support for the Apple Drive Setup
        utility.

In the next article I will write about my first steps in the system post boot and then bringing it to a more or less usable state. Stay tuned!