🇺🇸 Micro Palm Computers PC/4000 & PC/5000: Part 5 (DD50 Breakout Board) [TCE #0627]
27Thanks to #PCBWay for their ongoing support! https://www.pcbway.com/
I finally designed a breakout board for the DD50 connector on the PC/4000 and PC/5000, the idea being to try to figure out the pinout so I can finally get a machine to boot properly into MS-DOS 2.25! Even though it has DOS in ROM it still needs some files transferred across to actually boot ...
I've still not been able to find much solid, useful information about the company or their computers. I did stumble across the name of the founder ... Velton "Vel" Casler ... who sadly passed away in 2023:
https://www.lindquistmortuary.com/obituaries/velton-casler
Looks like they were used by the US Army Corps of Engineers at one stage:
https://ia600803.us.archive.org/35/items/DTIC_ADA299981/DTIC_ADA299981.pdf
One other scrap of info ... in June 1991 MPC were apparently paying Microsoft $22k/year for "ROM DOS 2.25 & 3.22" licences:
https://web.archive.org/web/20070211123428/http://www.iowaconsumercase.org:80/011607/0000/PX00784.pdf
With the breakout board I was able to figure out a few more pins, including eight pins connected to one side of an octal bus transceiver (74HCT245) that connects to a rather large chip by "PPS, Inc.". The chip is labelled "L1A2710 GA00001" and I assume it's a custom chip that crams in a lot of an IBM PC's functionality ... so I have no idea what the purpose of that interface is ... a parallel port?
I will update my Github with the little bit of extra information I've gleaned. I'll try to connect to the serial ports via an Arduino next and see if I can get some communication going.
00:14 ... New project: reference book
04:55 ... DD50 breakout board
07:06 ... Soldering Tunes
08:36 ... Construction complete
09:20 ... The PC/4000 and PC/5000 beasts
12:00 ... The pinout so far
16:49 ... Mysterious 8-bit port
19:07 ... Channel thanks & outro
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From previous videos:
The PC/5000 is the big brother to MPC's PC/4000 - handheld IBM PC compatible machines running MS-DOS.
Both machines run on the same hardware (an 80C88) and have 256KB of system RAM. The PC/4000 has two built-in 256KB storage modules whereas the PC/5000 has a built-in 1024KB storage module and space for a second module that can be added without opening the machine - mine has a second 1024KB storage module.
The PC/4000 is a 1988 manufacture and this PC/5000 appears to be a 1991 manufacture.
This particular machine came with a GE "Type SC-2 Smartcoupler" attached to the DD50 port. I have no information about this attachment apart from it having a catalogue number of "9937450G3". It may have had a barcode wand attached to it - it has a cable that has been cut ... ? It has an 8-bit microcontroller on board (a Motorola MC68HC70508CFN).
I have updated the pinout document on my Github with the Smartcoupler details:
https://github.com/0ddjob/MicroPalm-PC-4000
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