Rancho Technology RT1000-MC SCSI Adapter - 708D


Louis Ohland found the option diskette via IBM-PC.org. (Please be aware that I have not done anything more than to give these files a quick once-over. Use them at your own risk!)

Rancho Technology was verifiably still in business as of 2013. By mid/late 2014 they seem to have folded. The address once given for their place of business looks to be a residence if Google Street View is to be believed. Which kind of makes you wonder just how high the barrier to entry for hardware design and manufacturing really is...

If you are looking for an adapter that can provide a drop-in hard disk upgrade for a Model 70 or similar system where there are no standard power connectors available without soldering or modification then this is the one of a few adapters you can use. Use your best judgment when putting drives in a system with a smaller power supply (50, 50z, 55SX, 70). Also bear in mind that MCA bus connectors have limits on how much power can be drawn over them.

Rancho RT1000-MC

U5 - Labeled "PAL047 Rev A"
U8 - RTBios version 8.20P
U17 - NCR 53C400
U18 - Labeled "PAL 045 Rev A"
U19 10.000000 MHz (how many zeroes worth of precision do we need?)
RN1, 2, 3 - Removable resistor packs for termination, no identifiable numbers or branding.
C1 - 22uF capacitor

J1 - 4 pin power
P1 - 50 pin internal SCSI
P3 - DB25 external SCSI port


I found this in a Model 70 paired with a Conner CP1080 hard disk. The power cable has one connection at each end, but the SCSI cable has two plugs on it. Both cables look like they came with the adapter (or most likely a packaged upgrade kit including the adapter, since it has CMS Enhancements stickers all over it). One thing I have noticed is the vastly reduced heat output of this model 70...clear proof that newer drives not only run faster but also run cooler. Performance-wise this adapter seems a little slower than the uncached SCSI/A from IBM. It can and does use the system hard disk LED (if you have one).

There is support for making a "floptical" drive appear as drive A. The ADF says this about the feature:
"If you want your Floptical drive to be Drive A:, you Must choose the option 'Drive A: is Floptical' and follow the instructions in the users manual. Leave this option at 'Drive A: is NOT Floptical' if you have no floptical drives attached or another drive is drive A:."

Linux Support

Saskia Bormann said this about the adapter and Linux:

I haven't tested yet, but your outline says that there's a 53C400 as controller. These are normally covered by the driver NCR5380 (watch the nasty upper-case letters *grrr*), and you must provide the following parameters to it:
ncr_53c400=1 ncr_irq=[IRQ] ncr_addr=[addr] ncr_dma=[DMA]

It _should_ work. Because that driver wouldn't probably find the adapter on it's own, I'm writing a device manager that scans all slots for the adapter IDs, and looks which modules with wich parameters are needed.

Editor: I don't know whatever happened to any of this, or if the adapter is in fact supported under Linux. Saskia seemed to wander off not long after making this post. Modern Linux kernels have done the unthinkable and dropped support for Microchannel hardware.

Disk Capacity Limit (for disks under adapter BIOS control)

Okay, here's the sobering news. This adapter's BIOS is definitely not over 1GB capable. I hooked up an IBM DCAS-32160 to this adapter and powered up. The adapter BIOS identified the drive correctly, but when boot time came, the machine halted with "No Operating System". A Caldera DR-DOS 7 boot disk only saw 1GB or so of disk space. Worse yet, BIOS version 8.20P is the last version that was released for this adapter...and that comes straight from the people at Rancho Technology.

Still, a 1GB drive in any of a Model 50, 55, or 70 is a BIG improvement. You could also use two drives with the cable I have, as long as you're mindful of the power supply limitations in the previously mentioned machines.

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