75D First Steps.

[Paul Berger (Canada)]

(04-21-2021 09:06 PM)rprosperi Wrote:  

(04-21-2021 07:25 PM)dhe Wrote:  So last week, whilst waiting for batteries to come in, I gave the machine a good cleaning. Remember this was an ebay as is sale on the 75D.

Batteries came in, dropped them in place, and ...

Wait, what? Where's the on and off key?

Downloaded the manual, ah... on is attention.

While holding breath, hit the ATTN button, unit powered on, asked me for the time and date! W00T!

All keys seem to work, LED is crisp and sharp with no missing pixels and basic program ran to completion. I'd say I got lucky.

Now to check out memory and any optional ROM's that might be hiding.

Congratulations on a good deal! You can't win if you don't play...

By hidden optional ROMs, are you suggesting some ROMs may be installed inside? Though likely possible from a h/w perspective, and despite being fairly common for 41C and 71B machines back in the day, I don't recall this being done with the 75C/75D. No doubt that was partly due to the very high cost for these machines, but I'm also not sure if 4+ ROMs could be installed (logically) at the same time.

@anyone - is this feasible and do you recall this being done?

I don't think it would be feasible there is very little empty space inside a 75, but there would be room inside a pod, especially if you chucked the 300 baud modem, in fact I have toyed with the idea of a PMS like device inside a pod. I have built a read only ROM emulator but it still needs work, I will have to get back to that one of these days. My ultimate goal would be an expanded PMS like device that uses nonvolatile memory like FRAM.

Paul.