[rwg]

Woo, nostalgia! My father's TRS-80 Model 4P was "my" first computer back in the mid- to late-1980s, and I spent more time on it than an elementary school kid probably should've. (Every time a new issue of Family Computing showed up in our mailbox, I'd grab it and flip through it to see if whatever games were in that issue had TRS-80 Model III or 4 versions...)

The "P" in "Model 4P" stood for "portable" — it was a modified Model 4 that was shrunk down to something roughly the size of a sewing machine. It had a handle on the back. Tandy's advertisements proudly proclaimed that it fit in overhead bins on airplanes. I feel sorry for anyone who actually tried that.

As far as specs, the 4P had a 4 MHz Z-80, a minimum of 64 kB of RAM, one or two single-sided double-density (SSDD) 5.25" floppy drives, and an 80x24 text mode. There was an optional 640x200 monochrome graphics card, but it doesn't look like this demo is using that. (I'd bet it's using the graphics characters in the Model 4's 80x24 text mode — faster and less data to deal with.) If I'm remembering correctly, the SSDD disks held ~180 kB, so there's less than half a megabyte of data in play for this demo. I'm kind of amazed at the sound in this demo — I'd never heard the speaker in my 4P ever make any noises other than simple beeps.

Semi-related trivia: The "best" word processor for the Model 4, SuperSCRIPSIT, was laid out on its program disk in such a way that the drive head's stepper motor played something that almost sounded like a song when it was loading itself off of the disk. Even ~30 years later, I can still hear SuperSCRIPSIT's loading sound in my head...

[gp2000]

Good analysis. It actually uses the 64 x 16 text mode which has semigraphics yielding a 128 x 48 display. I only use 112 x 48 due to floppy disk bandwidth limits. I'm thinking of trying the 40 x 24 text mode. The 80 x 96 resolution would be a little nicer despite having two difference sizes of pixels. Or go the full 160 x 96 but that would require data compression of the video.

The hires adapter card has pretty serious write bandwidth limitations though there are possibilities if you're willing to put up with severe screen hashing.

It is pretty surprising how good 31250 Hz 1 bit audio can sound. As long as you set your expectations reasonably. "Was recognizable and didn't make my ears bleed too much" is about right.

[danjayh]

Seeing this on a 4mhz machine with such low specs makes me wonder what sort of impractical demos might be possible on modern equipment that harbingers of things to come 20-30 years. Can anyone think of anything off the top of their heads?

[erik]

I remember Kevin Kelly writing a blog post (that I can't find now) where he speculated that 30 years from now someone will come up with a clever way to get strong AI running on today's hardware.

[Dylan16807]

The fun part of demos these days tends to be making everything small or real time. Playing back a fullscreen video is impressive for old enough hardware, for recent hardware it's trivial and then it can display literally anything you care to prerender.

[hmottestad]

Maybe we get true 3d screens in the future.

Then todays equivalent would be to hook up 5 external monitors, take the backing off, and running a movie through them to get 3d.

To clarify. Make the screens semi transparent, then look through all 5 from the front.

[davelnewton]

The demo scene back in those days, and before, was nothing short of astounding.

[gp2000]

You recall the disk capacity correctly -- 40 tracks, 18 sectors/track, 256 bytes/sector. However, uses track-at-a-time reads to squeeze 200 KB onto each disk.

Track reads are a bit of a devil's bargain as certain data patterns cannot be written and other data patterns cannot be read. It still means more data though there is some possibility that conventional sectors with tight inter-sector gaps could do the job.

[Shivetya]

my nostalgia moment, I was taught COBOL on these machines back in 86. I remember them well as it led to my buying my first PC, a Tandy SX. Having used original IBM PCs at my parents home I was so impressed by "Tandy Color" and sound. One thing led to another and Turbo Pascal and Turbo C entered by programming life... and a Model 50 with old school gray scale screens that still looked amazing.

Which makes it all so sad having read that eulogy to Radio Shack here a few days ago.