HX-20 with unknown(factory?) RAM "mod"

[Kilrah]

I got myself an HX20 that seems to be a late model (newest chips are dated early '93 which seems pretty insane), and instead of the usual 8 RAM chips it has one single 32k Sony chip on a board that looks very original with similar markings to the mainboard in the externally accessible compartment, none of the other RAM footprints are populated, and there's a pretty involved set of bodge wires including a chip that are very professionally installed... looks like a late cost saving/replacement for harder to find chips.

Can't find anything similar around, has anyone ever seen this? BASIC reports the normal amount of free RAM for the stock 16K, I tried the initialization methods for the 3rd party 32K mods I found but still only 16K, just throwing this before I try to actually dig into how the mod has been done and whether accessing all 32K was even intended of it that's just what chip was most convenient to use as a replacement...

Besides the RAM situation that seems like a factory thing the unit was modded to remove the battery and replace it with a 5.5F supercap, and has an expansion module that instead of containing a standard memory/display interface has a completely custom board to interface to some industrial equipment along with an EPROM in the expansion socket with some software to use it (dated '94-95), from my research it looks like this was used as a data logger for medical instrumentation for... qualifying suppositories.

Seems rather insane to make a custom board and mods for what would have been a >12 year old machine at the point of the software date, maybe the product was older and had been designed around this or this obsolete machine by that time was a cheap way to just get the "receipt print" they were after instead of a full-blown PC with a DAQ card? So weird...

 

[spiderx]

Very interesting. I'm thinking this might be used to calibrate the suppository testers, not testing suppositories. That would make sense, as the person would most likely have to visit the site, so they need something portable, and test the tester to ensure it is working properly. It probably has those A,B,C, Start lines to generate fake data that they could use to verify operation.

 

[GeoffB17]

Yes, quite a few HX-20s went into the 'vertical' market with all sorts of mods, interesting to see another one.

The fiew of the ROM section suggests that there's a FISHER ROM installed there, I assume it's 8k, but if that's there, then it's likely that 32K RAM will not work. If you can disable the option ROM then it might be possible, but the extra wiring you refer to may mean that something is hard-wired so you'd need to suss that out.

My HX, which is sort-of still working, is capable of 3 memory configs. 16k RAM basic, then with the 16k RAM expansion 24k if the Option ROM is active (I've got a FORTH ROM in there) or 32k if the extra ROM is disabled. BUT in your case having all the RAM as one chip there might be problems?

So I guess you've got to try to work out what the 'bodge wires' do?

Geoff

 

[Kilrah]

I'm thinking this might be used to calibrate the suppository testers, not testing suppositories.

Yeah possible

The fiew of the ROM section suggests that there's a FISHER ROM installed there, I assume it's 8k

Yeah it's a 2764, contents attached

I've tried removing it and burning an EPROM with other known ROM dumps to put in place but didn't get them to run... not sure why but I didn't try reusing that one yet and only had bigger ones, probably just messed up putting the contents at the correct address.

In the meantime I got replacement ribbons for the printer and built a serial cable. Got to transfer things over the RS-232C port just fine, haven't been able to get either of the MH20 or flashx20 display/disk emulators to run though, they both just crash on the PC. Might need to try a Win7 machine or something..

The supercap mod is cool, as long as you remember to turn the machine off before disconnecting power it'll hold RAM for at least 2 weeks that I've tried so far.
Just a shame there's no cassette drive

 

[GeoffB17]

Hello,

I downloaded the .BIN file you posted, and I've just had a look at it.

I note that most of it is BASIC.

There's a header to the ROM, which may be more to do with mounting the code, but I'll check that further. Then there are two blocks of encoded BASIC, the larger one may be the main prog (this part is headed SUPERTEST) and a smaller piece which may be a subroutine or two.

Quite a lof of solid FF blocks, so the working code is well less than 8k.

Could turn the code into readable ASCII, or even into .BAS file that could be loaded 'normally)'?

If you do disable the Option ROM (using the DIP switch) does the system still NOT allow access to more RAM? Need to do a full RESET.

Geoff

 

[Kilrah]

Yeah I tried even removing that EPROM and turning (well leaving) the switch off, no visible difference.

That ROM does something weird, once I get it to appear in the menu I can't get into BASIC anymore until a full RESET so I can't dump it from there.

Haven't had time to look deeper into it

 

[Martin Hepperle]

The ROM is designed for the usual start address of 0x6000.
I have translated the BSIC program into ASCI format. It seems to be some very specific software for laboratory tests.

Martin

 

[Paralel]

The ROM is designed for the usual start address of 0x6000.
I have translated the BSIC program into ASCI format. It seems to be some very specific software for laboratory tests.

Martin

It would have to be. The requirements for working with a production machine that makes medical products is governed by a large volume of various standards and rules. The only industry that has to meet higher standards is probably nuclear.

 

[spiderx]

I did look up those suppository testers, apparently they heat up a suppository to a certain temperature and record how long it takes to dissolve. So, if it takes too long, or maybe too short, it would fail the test. I imagine there's a temperature measurement, some detector for the fluid that is inside the suppository, and some other sort of reference. Probably not very useful for anything other than measuring the melting point of a wax or other substance. You could probably rig it up to test out one of those dishwasher cleaners.