Chaps make working 6502 CPU by hand. Because why not?

Re: Michael Strorm & herman (thermionic valves)

The MTBF for valves can be pretty good if the heater current can be ramped up and down rather than 6.3 volts hitting a cold, low resistance filament. This is one reason why recent cars have a single headlamp bulb filament and a little motor to switch between main and dip; the avoidance of on and off switching increases bulb life and reduces warranty costs.

The discovery that lots of valves could be reliable if the heaters were treated gently was made by Tommy Flowers, and helped make Colossus possible. the Americans made the same discovery more or less independently.

Re: Michael Strorm & herman (thermionic valves)

25kW seems a bit much - if it was this then it equates to around 6.172W per valves, and typically that'll be 1.89W for the heaters (filaments) and 4.282W for the logic per valve. So it'd be 7.654kW total for heaters, and 17.346kW for logic. Assuming +170V as +ve rail for valve anodes, that'd make around 25mA anode current for a triode (and I'm assuming heaters/filaments at 6.3V, 0.3A for the rest) all as averages.

You could do logic switching using triode valves with a lot less than 25mA anode current - 2.5mA would be more typical. Remember, a power output valve might handle 6 - 9W in a typical valved radio of the time, and for the logic levels we don't need that power. So we'd be looking at, say, 0.43W for logic and 1.89W for heaters giving a total of 2.32W per valve total, requiring 9.4kW for all the valves...

Admittedly I'm looking at more recent technology here, like double-triodes on a B9A base such as the ECC83 and its data from around 1953, but even the earlier (double-)triodes in octal bases (physically larger devices) would fall in a similar ball-park.

Re: Stupid masochists.

"that you are more likely to cut off your fingers while sharpening the scythe"

Too true. After moving to the country my grandfather observed some men in the adjacent field using scythes. They didn't seem to be getting on too well so he asked them if he could have a look and told them the blades needed sharpening. Which he proceeded to do with a grinder and whetsone. One of them promptly cut his finger on the blade and I noticed they were proceeding with somewhat more care than before.

Re: Stupid masochists.

I think you may be right, EddieD. My confusion may stem from Mr Ploppy featuring in the episode 'Head', in which other body parts were lopped off.

Miserable state of the [ACTUAL] firmware.

Ah, but you're used to current tech - you'd lob a flash chip on the board and be done with it. In the 1980's (can't believe that's already some good 30 years ago), updating of especially portable firmware based devices was actually not something you did very often - a patch was a rare and momentous event because it meant the company in question had something wrong. It was not the occasionally rather shameful routine it now is for some companies.

On the PSION Organiser II, the extra issue was that EPROMS (at the time the only persistent reprogrammable chip) were typically a lot bigger and needed extra support circuitry to program so that wouldn't fit in the case.

Basically, the whole PDA idea (which is now part of what you carry around in your smartphone) started with that silly device, and it was (and is) fantastically functional for its simplicity. I actually came across a Palm pilot too a few days ago as well when I was digging for some electronics, but to me that was better done by Sony with the Sony Clie NX70, also because that was pretty much the first time a PDA and WiFi were combined.

I wrote quite a few little programs for my C64 and VIC20 using DATA statements, you converted all your OP codes into decimal and put them in a data array, then had a mini BASIC program that called SYS something which ran your data as machine code. The speed difference between a character bouncing around the screen in assembler compared with C= BASIC was amazing.

Hand-assembled Code

Some 35 years ago I had two (yes, 2!) PDP-8/e computers with a tape drive, disk drive (cabinet one, all of 10 MEGAwords!), printer (line), and a couple serial lines - one a VDU terminal and the other an ASR33 teletype - as a home system!

I already knew assembler, for the 6502 and the 6800-series processors, but I had no OS or anything for the PDP's. So I set about writing one, so that I could end up using these machines for processing radio propagation data from regular observations. No development tools, just the PDP-8/e manuals and codes.

Fisrt I had to write a bit of code that would take serial characters as octal input (it is a 12-bit machine) and write this word into successive memory locations - this was done using the front-panel switches, word by word.

Then it was time to write some code that would allow me to write whole segments of octal from the keyboard of the serial device I chose, usually the VDU terminal. The next bit of octal 'code' was a routing that would take that segment and write it to the magtape as a record, skipping till after a 'long gap' on the tape so I could eventually load back these segments one at a time how I wanted.

Once that was done the 'semi-serious' work began - first of this was actually to *write an assembler*, which for this machines' instruction set and layout was not too complicated. This assembler, a 'program', was written to a new magtape and also to two copies (play safe here!) of punched-paper-tape.

After that, the assembler was the main tool to write I/O routines for the magtape (proper, better), the disk (elementary), and the printer. Once that was completed the 'really serious' work began, I wrote an executive, then a filing system of my own, then an operating system on top of those.

Finally I had a running system with storage volumes (floppy disk never got added but all principles were in place and it didn't make any difference anyway), and with interfaces to assignable peripherals (e.g. equivalents of mount and unmount and different peripheral classes and parameters) - and I did go on to write some of the programs I ran to do the original work I wanted to do.

Eventually the "common" P.C. came along and was easy to interface with the radio hardware I used, plus it used a LOT less A.C. power than the roomfull of computer gear that was the PDP's, so eventually I got rid of most all of that equipment as there's a limit to how much one can keep, at least in the 'sane' world.

Still, even as I look back all those years, I'm sure that I learned quite a lot and gained a valuable insight into what certain colleagues of mine have to do in their work and where the 'trip-up-points' can be lying around; in any event it was definitely a memorable experience at the raw end!!!

Re: I remember writing the processor!

Hey we did that too, for a final year project, would have been 1990. Ran on a Macintosh and had simulated IO and interrupts. In the real world I was a Z80 man though.

Those were the days. The closest I get to assembler now is watching OpenSSL build in a cmd window.