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DimensionDude
June 6th, 2005, 12:12 PM
After yet another keyboard failure on the Dimension 68K, I decided to find out once and for all why frequently used keys would quit working. I dismantled the latest victim and was not pleased.

The "contact" for each key is a disk of what appears to be mylar glued to a cylinder of foam. The foam wasn't made to last for 20+ years so during use it just crumbles.

Any ideas on how to fix this? The Dimension can't use a standard IBM keyboard, I've tried (XT and AT). The first idea I came up with was to punch cylinders out of a foam block and glue the mylar disks to them. I guess this would work but it would take a while to get done.

I'm off to research these (mumble) keyboards, maybe an existing XT or AT keyboard can be modified...

Kent

Terry Yager
June 6th, 2005, 12:19 PM
Couldn't you just get another (Keytronics?) keyboard for the XT and swap-out the ROMS? IIRC, the only difference I found inside them was the chips' version numbers, everything else matched up.

--T

DimensionDude
June 6th, 2005, 02:35 PM
I've been through the Dimension system reference manual, it appears that the keyboard sends ASCII code in asynchronous, serial format. 300 baud. The "text" keys are standard ASCII, the functions keys and others are assigned codes. Key combinations are assigned unique codes.

More research is in order. I may yet wind up gluing bits of foam and mylar.

Aren't old computers wonderful? :?

Kent

DimensionDude
June 6th, 2005, 04:25 PM
I have a working keyboard again :D

Took apart all my spare keyboards hoping that one of them would have a socketed rom. Didn't find one like that, but I did find one that used the same mechanism, little shiny discs glued to a foam cylinder with a clear plastic disc on the other end.

Popped all those little suckers out and put 'em in the ailing keyboard. Now I'm wondering if those little foamy doodads are available anywhere.

Also, if anyone has a Keytronics XT keyboard with a socketed rom, I'd be interested.

Kent

mbbrutman
June 6th, 2005, 05:22 PM
Interesting system - just looked it up and did the reading. How did you come across it?

As far as the keyboard goes, that thing is an oddball. It's a keyboard that sends ASCII codes instead of scan codes? In that respect it is half of a tty already!

Apparently the Dimension didn't do anything particularly well .. do you have the board that makes it PC compatible? If so, how well does it work?

Terry Yager
June 6th, 2005, 06:51 PM
From my experience with them, the IBM compatibility is not much better than 50% or so. Usually, it'll run "well-behaved" programs that use only system calls, and not write directly to the hardware, but of course, nobody wrote programs like that because they're much too slow. It can handle your Lotus 123, and dBase-type stuff... well, sorta...
The Apple and CP/M-80 emulations are much better than the PC, running most programs written for those systems.
It has a ROM-based BASIC that is AppleSoft (integer?) compatible, but the AppleSoft is just a subset of the D68K's native BASIC, which takes advantage of the 68K processor's power.
Where the D68K really shines is when running in native mode. It is a very capable (and fast) CP/M-68K machine.
Well, that's my $0.02 worth, whadda you think, DimensionDude? Sound about right?

--T

DimensionDude
June 6th, 2005, 08:04 PM
Yep, the ASCII keyboard thing is kinda weird. It feeds into one port of the UART...don't know what they were smoking when they came up with that.

Hmm...half of a tty, hadn't thought about it that way...

Terry has pretty much hit the nail on the head, the IBM emulation is weak. I've run text based stuff (First Choice comes to mind) and even a few games (Zaxxon). Speed is equivalant to a 5150, which is something seeing as how it has the same processor as a PC. Overhead doesn't seem to be a factor. However, anything that doesn't play nice and makes hardware calls will crash the emulator. But you can usually get back to native mode without a reboot.

I've used the Z80 mode to run WordStar80 so I could look at the documentation that's on disks. Seemed speedy and stable.

Not much experience with Apple, never had one. There's a disk of Apple utilities amongst the stuff, I've played with it a bit. Can't give an opinion one way or another there.

I used to work in a tv/vcr repair shop, the owner acquired all this Dimension stuff. I bought it from him when he needed the space back and was threatening to dump it in the river.

There'll be more info when I get my website finished. Getting things somewhat organized, cleaned, and photos taken in preparation for it. Never "authored" a web page, either, learning as I'm going :D

Incidentally, I discovered that my scanner works much better when powered up :oops:

Did y'all know that making a call to an unpowered scanner will lock up Windows98SE? Wish the Dimension was internet capable...

Kent