Tandy 3-in-1 expansion review for the 1000HX and EX

Last Updated on February 4, 2023 by Dave Farquhar

The Tandy 3-in-1 expansion for the Tandy 1000 EX and HX make these compact vintage PC compatibles much more useful. Here is my experience with this device, and some tips.

Two versions of this device exist. The first expands the memory to 640K and provides UMBs, compact flash for mass storage, and an RS 232 port. These are usually available on Ebay for around $100 US. The newer version 2 of the device adds all of that as well as a standard parallel port.

Tandy 3 in 1 upgrade review
The Tandy 3in1 by Rob Krenicki is an essential upgrade for a Tandy 1000EX or 1000HX.

The standard parallel port is useful because Tandy’s parallel port uses an edge connector rather than the more common DB25 connector, and some of the signals are also different. This isn’t a problem for most printers, as long as you can find or make an appropriate cable. But if you want to connect other parallel port peripherals, such as a Xircom network adapter, or a parallel port sound card, this can be a problem. Having a more standard parallel port makes life much easier.

Unfortunately, to my knowledge, nobody is making the four-in-one version and offering it for sale, just the three in one version.

Memory expansion

The most essential function is expanding the memory. Tandy provided and expansion board that plugged into its plus expansion connector, but not everyone bought that board, so there are more unexpanded Tandy 1000EX and 1000 HX computers floating around out there than there are memory boards. The computer was extremely inexpensive, especially if you bought one on sale with a bundled monitor, but Tandy didn’t cut you much of a break on the upgrades.

The original board provided a DMA chip that sped up floppy access. The 3 in 1 board doesn’t provide that. But the consolation prize is that it provides memory in the otherwise unused UMB space. DOS doesn’t officially support UMBs on 8088 systems, but you can use a third party utility to enable them and load DOS high.

This config.sys works as a starting point if you run DOS 5 or DOS 6.x:

device=c:\tandy\use!umbs.sys D000-EFFF
device=c:\tandy\dosmax.exe /P:-

You can get use!umbs.sys from this Simtel mirror (scroll to the end) and dosmax.exe from here. With a configuration like this, it’s possible to have 600K of available conventional memory, which is impressive on a Tandy 1000.

Compact flash

The compact flash port is the main reason I bought this board. Swapping floppies around gets tiresome, and let’s face it, the floppy drives and media aren’t getting any younger.

Tandy didn’t offer a hard drive for the all-in-one machines. Some people rigged up their own solutions, and there were some third party solutions for adding an external drive. But for me, having a compact all in one machine of this class with reliable mass storage is appealing. It gives me about 90% of the functionality of a larger 1000SX in a much smaller space. The only thing I can do with a larger system that I can’t do with my 3-in-1-equipped 1000 EX is put it on my network.

Putting the compact flash card in a modern PC and copying the files over to it is the way around that. I can also use the RS232 port to transfer files to it.

Drive access with the compact flash is pretty quick. And if you upgraded your CPU to a V20, you can update the BIOS to nearly double the speed of your C drive by taking advantage of the V20’s instruction set.

Caveats with large partitions

You can get a 2 GB compact flash card for $10, but that doesn’t mean it’s the best match for an 8088-class machine like a Tandy 1000. But there’s a solution for that.

The BIOS on the card supports a drive that size. But keep in mind DOS versions prior to 3.31 were limited to 32 MB partitions. And if you do run a newer DOS version, that first write or directory listing induces a 25-second delay as the lumbering 8088 CPU calculates the free space. The popular V20 CPU upgrade doesn’t noticeably speed that up, either. One workaround is limiting your C partition to 128 megabytes or even 32 megabytes to keep things tolerable.

Another solution is the utility FREESP written by a Canadian programmer and retro enthusiast who goes by Chartreuse. FREESP precalculates the free space using a faster method than the one built into DOS. You can run FREESP C in your autoexec.bat to reduce the delay to closer to 2 seconds and move it into your boot sequence. And if you can spare 1.2K of conventional RAM, you can use the terminate-and-stay-resident version, FREESPT, which intercepts the DOS routine, quickly performs the calculation, and populates the disk parameter block.

DOS 6.22 seems to be the most common choice with this card. Tandy didn’t support it, but Tandy doesn’t support these machines at all anymore either. You can use DOS 3.31 to get a 1980s feel while getting your large partitions, but DOS 6.22 works better overall, as it provides better support for the RS-232 port.

RS 232 port

There wasn’t a ton of Tandy software that used a mouse, but the system looks incomplete to modern eyes without one, and some of the later software that ran on the machines is much nicer with one. The RS-232 port allows you to connect a standard mouse other than Tandy’s odd color mouse that plugs into the joystick port.

The RS-232 port with DOS 3

The only caveat with this is the RS232 port on the 3-in-1 doesn’t seem to get along all that well with DOS 3.3 or 3.31. Microsoft’s Interlink utility will run on DOS 3, but the combination of Interlnk, DOS 3.31, and the serial port don’t get along. That’s a shame, as it would provide a workaround for loading files onto the Tandy from a newer machine without using floppies.

An alternative tool called File Maven for DOS did work and it enabled me to transfer files over RS-232 from another PC.

I also found Microsoft and Microsoft compatible mice don’t like the combination either. I do have one mouse with a switch that toggles it between Microsoft compatibility and Mouse Systems compatibility. That mouse does work  in DOS 3.31 with the 3-in-1 card in Mouse Systems mode.

The hilariously ancient looking Logitech c7 is Mouse Systems compatible if you want something period correct that looks the part and is fairly easy to find. So is any random three button RS 232 mouse you are likely to find at a thrift store or estate sale today. And while very few of cheap 90s mice won any ergonomic awards, they were better than a mid 1980s mouse would be.

The RS-232 port with DOS 6

Under DOS 6.22, the situation is different. I can use whatever Microsoft compatible mouse I want under DOS 6.22, including my nice ivory Dove bar type from 1987, which looks pretty good with a Tandy and is period correct as well.

So even though Tandy didn’t recommend DOS 6.x on Tandy 1000s, I find DOS 6 lets me use my Tandy 1000EX the way I want better than DOS 3 does.

Final thoughts

Vintage computers are like having a vintage car. They aren’t as reliable as a new one. If you don’t want to mess with the quirks of real hardware, there is nothing wrong with emulation.

I find the MacGyver element enjoyable, at least sometimes. And if I’m not in the mood to be MacGyver, I can find something else to do.

I definitely recommend the Tandy 3 in 1. Tandy 1000s were quirky machines, just compatible enough with the rest of the market to gain acceptance, and just different enough to have a slight market advantage for a few years. I hesitated to run DOS 6.22 on mine because I’d heard Tandy didn’t recommend it. But loading DOS 6.22 solved the problems I was having.

Overall, I recommend it, and as I learn more about using mine, I’ll be following up with more. None of the things that I ran into are showstoppers by any means. If you have either of the all-in-one models, this single board is the best upgrade you can get for them, bar none. It comes down to whether you want to buy one or feel comfortable assembling one yourself. A desktop version of the 1000 or 1000SX is still more expandable, but the EX or HX with this board is almost as good, and takes up much less space.

If you found this post informative or helpful, please share it!

2 thoughts on “Tandy 3-in-1 expansion review for the 1000HX and EX

  • January 7, 2023 at 3:25 pm

    Thanks for featuring my design! Just to clarify, the 4-in-1 design includes a Real-Time Clock as the 4th item, not a Parallel port. It also was switched over to a mostly SMD design rather than Through-Hole parts.

    The 3-in-1 Version 2.0 includes a multi-IO chip which adds a second RS232 as well as a full Parallel port. I still consider it a 3-in-1 as the 2 serials and parallel are all handled by one main chip.

    Unfortunately, nobody has taken up the task of building either of them for sale. Only the original is being sold by a seller in Canada right now.

    What mouse driver are you using under DOS 3.3 that does not work with Microsoft mode mice? I ran into a lot of issues with CTMOUSE under earlier DOS versions, so I started including MSMOUSE 7.0 driver instead.

    • January 14, 2023 at 11:03 am

      Thanks Rob! Yes, I was using CTMOUSE with limited success, except in Mouse Systems mode. I switched to a Microsoft driver but didn’t try version 7, I had a copy of 6.24 and a couple of earlier versions. Switching to DOS 6.22 has solved that so I just rolled with that.

Comments are closed.

%d bloggers like this: