Saturday, May 19, 2018

Design of homebuilt TTL PC

Peter F.  I always think about your work ! 😍Is it full in TTL logic ? How is the simulator going ? I dream with that and with relay computers. As I told you my first computer was a 4 bit ttl I made at 12-13 years. With that 74181Alu, I still have my TTL collection from that time(not LS, "real heavyweight TTL" they are terrible power hungry!) . Regrettably the minicomputer with 4x4 rows of leds...was scrapped.

Bill V. My project was similar to yours. I used three 74181's and a chip, I forget which, that tied them together. It was all TTL, mostly open collector as that was easier to wire-or together. I made it 12 bits as that was enough for addressing the 2102 memory chips and giving me lots of options for instructions. Four of the 12 bits in the instruction register went right to the 74181s so I had access to all commands.

I'm sorry now I scrapped the original slit-and-wrap circuit boards but I still have all the TTL IC's somewhere.

I hope to wire-wrap a replica of the original and eventually build a new and improved version with better TTL - like HCT or maybe CMOS.

The emulator is advancing a little every day. It's a wonderful mental exercise working with the emulator and thinking of the tradeoffs between actual hard coded in TTL instructions and other new and enhanced instructions in software. The software is so easy but it won't eventually run in the upcoming computer.

Monday, May 14, 2018

Fwd: Posting to blog from email

Second try - perhaps I didn't save the configuration fast enough earlier.

Yet another way to make all the tools work together. This is a step.
A small step. A small step in what is hopefully the right direction.

Stay tuned...

Thursday, April 19, 2018

More on TTL Computer

I'm not the only one with a home built TTL computer.  Some other folks have spent years and done incredible work.  Check out projects like the Gigatron and Magic 1 from the links here

Here's a couple better pictures of the front panel of my silver box TTL computer.

One front panel light (LED) is connected to a 3909 circuit.  That's a special low power blinker that just blinks the light every second or two for over a year.  That's the first thing to get running.

Monday, April 16, 2018

Homebuilt Computer

A long time ago, in a galaxy far away (Montana) I built a computer.   Not plugging in boards but rather building the boards themselves.   No microprocessors - just basic TTL integrated circuits.   I saw the diagram for an old HP computer and thought - if that's all there is, I can do that.

So I did.

It worked - very slowly.

Then I took most of it apart to save the IC's.  (silly silly silly...)

Now that the Force has rewoken and the last Jedi returned - it's time to rebuild the old computer.

There's a lot to this and it's going to take several forms of both hardware and software.  So it's going to take a while.   That's part of the fun.

Here's my computer and I at a computer show of sorts in Bozeman back in 1978...

The SWTP CT-64 terminal and cassette deck are misleading.  The homebuilt TTL computer in the silver box with the rows of lights never did have a serial interface.  That's yet another challenge for the new versions.

Thursday, March 29, 2018

Higher Low Speed Easy - 4800 baud APRS

Onward to the future.   I realized yesterday that all the pieces were at hand to start running 4800 baud APRS packet as well as good old 1200 baud.  It simply required a small tweak to an existing configuration of the DIREWOLF software modem.  Thanks to the ease of working with windows audio systems - both the new DIREWOLF modem and the existing UZ7HO (1200 baud) system can run at the same time with the signal source - the 6 pin mini-din data jack on a Kenwood D710A.  The built in TNC on the D710 is running as a 9600 baud digipeater on our UHF packet channel.

Now to advertise it and see if anybody else wants to experiment.

Bill, WA7NWP

Wednesday, March 28, 2018

We'll be back...

2017 ... So much to say..   Not sure yet where to say it.   Perhaps moving all content here to the homegrown content system.  Stay tuned and 73's (t)...

Update 3/28/18 - the homegrown CMS is coming along slowly.  I will eventually move everything there.  In the meantime I'm going to start posting here again just as a place to keep things online.

Friday, June 10, 2016

CQ 29.6

To the PNWVHF discussion group

> Ssb/fm 50, 144, 432 mhz

Not that the typical VHF bands are crowded, but do thoughts of operation ever drop to 10 meters.  The FM segment, typically 29.6 simplex, has operating characteristics similar to FM on 6 meters.  Most of the time it's dead quiet, then it opens up and the world comes rolling in.

I recently discovered, acquired (thanks HRO Portland) and yesterday installed the Diamond CP-610 vertical for 6 and 10 meters.

My idea is to use this for typically FM operation.  Scanning with the FT8900 when I'm in the shack and switching over to old slow packet when I'm not in.

So far, without trying to key up repeaters, I've worked the remote base in Shelton and that's it on 52.525.  Calling and calling on 29.6 returns nothing but static.  Surprising how much static there is even on FM.

So - anybody else playing on 29.6 and 52.525?

Bill, WA7NWP