Sunday 27 February 2022

Minstrel Final Edition Kits

At the end of last year, I put together as many Minstrel 2, 3 and 4th kits as I could. The limiting factor was availability of parts. An increasing number of parts are out of stock everywhere, and the stock situation does not seem to be improving. Microchip appear to have a rolling 12 months estimate for most of their microcontrollers and EPROMs. RAM, voltage regulators, and logic chips then started to go out of stock and it became difficult to complete any of the kits.

These kits are sold via The Future Was 8 bit, I am very grateful to them for doing that, as it has been able to keep me going through these difficult times. 

We have branded them Final Editions, as these are the last of this sort of kit we are likely to be able to make for the foreseeable future.

To celebrate that, I wrote a nice new manual. Each of the kits feature a newly written 100 page spiral bound manual covering building and testing of all the kits.

I understand TFW8b may be offering remaining stocks of these manuals for sale separately for existing Minstrel owners. 

When I used to sell these myself, I had all sorts of options, but I have no practical way of shipping or dealing with all the import / export duties etc. as the UK is a bit broken at the moment. To keep things simple, there is a set menu with a few options.

Kit A) Minstrel 2 with Keyboard

This is a ZX80 compatible computer kit. 3.25MHz Z80, 16K of RAM and an integrated 40 key keyboard. This has the option of running the original ZX80 4K integer BASIC, as well as the later ZX81 style 8K floating point BASIC. It comes with keyboard overlays for both versions of BASIC.

This follows the ZX80 design, using TTL chip, with a few updates. The ROM and RAM are more modern single chips, and the voltage regulator is a switch mode 7805 replacement. There is also one additional TTL chip and some extra circuitry to generate a more compliant monochrome composite video that the ZX80 originally did.

The minimalistic design meant that the Z80 spent most of it's time drawing the screen, and when it had to run any code, it would stop drawing the screen. It does not support the ZX81 mode where some code is run during the blank portions of the screen, but many games use similar code to achieve 'flicker free' graphics. Read more about How the ZX80 Works.

Kit B) Minstrel 3 with Keyboard

The second option is the Minstrel 3, this is a ZX81 compatible computer kit. 3.25MHz Z80, 32K of RAM and an integrated 40 key keyboard. This runs 8K floating point BASIC and supports the NMI controlled fast and slow modes, to allow code to run whilst the blank bits of the screen are being drawn, to avoid the flickering when keys are pressed that the ZX80 suffered from.

This is a new design with improved video output and support for various high resolution graphics modes so you can try out new games pushing the limits of the ZX81.

As well as old favourites.

HC logic chips are used throughout, so the current consumption is about half of the ZX80 and the 7805 regulator can be used without a heatsink. Read more about the design of the Minstrel 3.

Note this version does not include the Minstrel ZXpand, and those are not available separately. 

Kits C and D

These kits were released when this blog was offline, so unfortunately the other two kits have now sold out. I do not expect to be able to make those again, so I am afraid that is the end for the Minstrel 3 + ZXpand and the Minstrel 4th.

At the time of writing, there are still some Minstrel 2 and a few Minstrel 3 kits left, so if you want one of those, I would get over to The Future Was 8 bit now and order one.

There are new kits in development, I hope that by the time they are ready to go, parts availability will have returned to a better state and I will be able to start making kits again.

Sunday 20 February 2022

The Mini PET 40/80

Introducing the Mini PET 40/80.

This is an improved version of the original Mini PET, and includes all of the optional features of that kit, the colourful deluxe keyboard and perspex baseplate and clear top panel.

The kit is still based on all modern through hole parts. The heart of which is the WDC W65C02S CPU. It is compatible with most software for the Commodore PET from the 2001 series through to the 8032. 32K RAM is provided as standard, the maximum the PET can support (without going into paged RAM). It does not have a 6545 CRTC, so some graphical demos will not run, but pretty much everything else will.

This side hasn't changed much, address decoding, IO and CPU. I swapped out a 74HC10 that used to be there for another 74HC138. It does the same job, but is one fewer part on the BOM.

This section doesn't look very different, but lots of work has gone on here. The video RAM is now 2K bytes, and supports 40 or 80 character modes, with a 74HC257 being used to select the dot clock. Gone is the 74HC74, with the character inversion now hard coded inside the character ROM. There are more DIP switches, as there are more video mode options. For a 40 column display, the CRTC microcontroller has 16 clock cycles to read the character code from the video RAM, looking that up in the font ROM to get a bit pattern and load that into the shift register. For an 80 column display, that is only 8 clock cycles, so the firmware had to be completely rewritten to achieve that. It is now using only 6 cycles per character to allow loops to be used rather than the previously unrolled loop code.

This section is mostly new. Some old school 4000 series logic running at 9V providing soft power on/off, and also controlling the 40/80 column selection. The new style 8 pin regulators replace the 7805 and TIP29s. Sad to seem them go, but would have needed additional MOSFETs to switch those off during standby. The two red LEDs show when the motor power is activated on the two datasette ports.

The Mini PET 40/80 is wider than the previous Mini PET, adding a second datasette connector to the rear. That allows you to use an SD2PET SD card disk drive and a datasette drive without having to unplug anything.

There are more video modes, monochrome composite video in PAL and NTSC, support for 9" or 12" PET monitors and a new 9 way D monitor connector to the side for RGBI/CGA/MDA monitors. I have been surprised that I have not been asked more often if that is VGA. It is not, that would have needed a second crystal oscillator and a faster microcontroller to deal with the line and frame rates required for VGA. Power is from a 9V DC centre negative supply (included in the kit).

There are now four function keys down the side of the keyboard (I wonder where I got that idea from - maybe I should make them orange or grey?). Soft power on / off controls the new power circuitry, the reset button and NMI Menu button are now full size keys and there is a new 40/80 button which changes video mode, changes the ROM set and resets the Mini PET so you can easily switch between 40 and 80 column systems.

The Mini PET 40/80 has it's own version of BASIC, Mini PET BASIC 4.1, adapted from Commodore BASIC 4.0 with a few extra commands, and built in features including a file browser, a full self test and a DOS Wedge which is permanently active (no need for a SYS call or to load from disk). 

The self test can be started from any of the versions of BASIC, or selected via the DIP switches. This will cycle continuously to act as a burn in test.

Pressing the Menu button brings up the built in file browser to allow you to load files more quickly from an SD2PET or other disk drive.

The big change is the 80 column mode. Great for text adventures, programming and business software. Seen here with the optional 2 pixel gap between lines enabled.

The extra space makes text heavy screens easier to read.

But of course, 40 column mode is still the default, ready for all the usual games.

Or new ones

Attack of the PETSCII Robots - The best game ever written for the Commodore PET [citation needed]

Or there are my own PET remakes of Tut-Tut

and 3D Monster Maze

And with 80 column mode, you can use the cheat mode in 3D Monster Maze to get a Pterodactyl's eye view of the maze.

See how the maze is drawn and how Rex moves and even find the exit.

Or fully show off the 80 column mode with Cheese and Chive

The best game ever written for the 80 column PET.

The Mini PET 40/80 is a self assembly kit, not for the novice, some soldering experience is necessary.

To help you along with the process, the kit comes with a lovely spiral bound manual

Being spiral bound is idea so you can lay it flat on the bench as you are working.

The Mini PET 40/80 kits are available now from The Future Was 8 bit

I don't know at this stage if this will follow the Minstrel kits in being the Final Edition. We are will waiting for IC availability will return to previous levels. When I will see this many microcontrollers again?

So if you want one, get yourself along to the The Future Was 8 bit now

Also available: The Mini PET 40/80D. 

Read more about that here:

2024 Update

All the kits at TFW8b have now sold out, but various versions are still available from my SellMyRetro store.

See here for links:

Tuesday 8 February 2022

The Blog Returns

I am slowly bringing the old blog posts back online.

Each post will have a message at the top explaining its status.

This is an old post, preserved for reference.
The products and services mentioned within are no longer available.

With the exception of the items listed below, I am no longer able to supply the products these blog posts describe and promote. Component availability and shipping problems mean it is no longer possible to get the parts required, or post the items out worldwide, I would ask that you accept that and refrain from requesting anything not listed here.

Some items available via the Tynemouth store at the Future Was 8 bit:

"Final Edition" Vintage Computer kits - whilst stocks last!

Pre-assembled products
  • Mini PET 40/80D - (NEW) Replacement mainboard for Commodore PETs, supports 40 and 80 column mode, normal and business keyboards. Built in SD2PET SD card drive
  • PET ROM/RAM - Replacement ROM and RAM for Commodore PETs
  • SD2PET - IEEE-488 SD card drive for Commodore PETs
  • VIC 20 Penultimate Cartridge+ - Menu driven RAM and ROM cartridge for the VIC 20
Games on tape
  • 3D Monster Maze - The best game for the ZX81 remade for the Commodore PET / Mini PET
  • Tut-Tut - PET / Mini PET version of David Stephenson's excellent ZX Spectrum game
Digital downloads of the games are available via my store
Anything not listed above is unfortunately no longer available. And no, I don't have just one left that I could sell you. And yes, I have checked down the back of the sofa. TFW8b support cannot help with any of my other products, only the ones they currently sell, so please do not ask.

Whilst the blog has been offline, I have been posting via my Patreon. I will start to bring some of the older posts from there onto here once I have finished working through the existing blog posts.

The new posts will be highlights of the posts on Patreon. I will continue to provide early access to the new posts and exclusive behind the scenes development blogs and updates on the Patreon. 

You can follow along on there if you like.

Update: Most of the posts are back online now. I have decided not to bring back any of the USB keyboard posts, as they create too many enquires.