On Sat, 1 Feb 2025, Frank Leonhardt via cctalk wrote:
I think the Epson MX80 was responsible for standardising the Centronics interface :-) Not only was it TTL only and therefore easier to implement in hardware, but it was much faster than RS-232. You could get other interfaces as add-on boards, including RS-232, Apple, TRS-80 and IEE488. I believe they got a 50% of market share for printers with this, from a standing start.
The IBM "Graphics Printer" was a REBADGED MX80, at least for the first few years. That might also confuse any data about how many MX80s there were. I don't know whether the IBM printer had any minor internal (firmware?) differences from the commercially available models.
IBM used a DB25 socket for their printer port at the computer end, (male on the card for serial, female on the card for parallel "Centronics") THAT, of course caused some idiots to attempt to use the parallel port for serial and vice versa. "I just need a 'gender changer'!" :-)
Similarly, IBM used DE9 male sockets for serial (previously a DB25 male) and DE9 female sockets for CGA, MDA. The earliest Microsoft mouse had DE9 female plug or DB25 female on its cord for serial, and DE9 male plug on the cord for "BUS mouse". THAT, of course led some users to accidentally plug a bus mouse into a DE9 video socket, and vice versa. They later changed the design, changed the name to "Inport", and changed the connector to Mini-DIN so that it could be confused with PS/2 connectors.
TRS80 used a 34 pin card edge (in order to be confusable with their 34 pin card edge for floppy disk) on the "Expanion Interface" for printer, but 36 pin Blue ribbon at the printer end, for most, but not all of their printers. The pinout was close enough to permit insulation displacement crimp on connectors on a ribbon cable (cable number 26-1411? or 26-4401?) Radio shack also came out with a special adapting cable to connect to the 40 pin expansion connector for those who didn't have the Exansion Interface. TRS80 also had more of the same issues of multiple same connectors for different purposes, such as Power/Video/Cassette
Sorry, if I have errors in this (unrefreshed dynamic wetware memory) -- Grumpy Ol' Fred ci...@xenosoft.com
