UK101 Hardware Modifications Archive

[Seldon2k]

After creating this forum viewtopic.php?f=45&t=13550 to act as a UK101 Programming Resource
I have just thought of the hardware modifications that made that necessary!

This forum is to be a repository of the various mods from PE Magazine, the CUA newsletters, and other sources to help people who may
either wish to 'upgrade' their UK101 boards or just puzzle out what has been done to it before they acquired it.

I hope other will contribute any scans or hardware tips.

[BigEd]

I did a clock speed mod. Probably like the one described here:

Modifications

Because of the simple nature of the hardware, it was very easy to modify the machine. Some very common modifications included:

• External power supply
  There was an on-board power supply (it just needed an external transformer), but it was under-rated and the voltage regulator chip was prone to failing. So it was quite common to remove it and use a rather better external power supply.
• Overclocking the the CPU
  The 6502 had a 1μs cycle time and used a 1MHz external clock to generate it, however most CPUs could run quite happily at faster clock speeds. Since the UK101 had all its clock signals derived from a single 8MHz timer it was easy to find a 2MHz signal and attach it to the CPU clock pin, effectively doubling the machine speed.
• Improving the video
  It was relatively simple to double the video RAM to 2K and then display 32 lines instead of the standard 16, which was a very useful extension.
• Increasing the cassette baud rate
  The standard cassette interface ran at 300 baud which was reliable but pretty slow. It was simple to double this to 600 and even double again to 1200, as long as you used a decent quality tape recorder - running the CPU at 2MHz also helped a lot when trying to get 1200 baud to work reliably.

[trev-ham]

I have done several mods to my test UK101 as seen in the image, they are;
Multi-Monitor board (switchable)
ROM/RAM board with switchable 1Mhz/2Mhz clock
Video RAM adapter to accept 6116 SRAM (replacing the existing 2114's)
Programmable Sound Generator (as described in Practical Electronics Sep 1980)

These mods have been designed to have little or no impact on the original PCB. If anyone is interested I have a small number of bare PCB,s available for a small donation.

Cheers
Trevor

[flaxcottage]

Love those circuit boards.

I'd be interested in the ROM/EPROM board that sits on the 6502 socket. It makes my veroboard concoction look positively primitive.

I'd PM you but since you have only 4 posts you couldn't reply. If you contact an administrator maybe they will let you PM.

[JonTr7]

Hi Trevor

I'm interested in a programmable sound generator board.

John

[IanB]

I previously posted this in another thread but as you are collecting mods in one place, here's my "no snow" modification which was published in the December 1981 issue of PC World:

This mod might not work when running the CPU at 2Mhz

[trev-ham]

Hi Ian,

I did try this 'no snow' mod a while ago and it did not work at 2 MHz on my UK101 so abandoned it.

[IanB]

I did try this 'no snow' mod a while ago and it did not work at 2 MHz on my UK101 so abandoned it.

I couldn't get my UK101 to run at 2Mhz so never tried it but I'm not surprised it doesn't work as it relies on both the character clock of the video system and the CPU running at 1Mhz so they can both access the RAM on different phases of the clock. It probably wouldn't work on the Superboard either as the character clock on that is 500Khz.

It should be possible to get it working at both 1Mhz and 2Mhz by gating the signal going to pin 9 of IC28 with the 1Mhz clock but I haven't looked at the exact timing details of this.

[tinplatepete]

Hi Trevor.
I am also intrested in your PSG board.

Peter

[tinplatepete]

I did Ians no snow mod back in the day and it worked fine on 1Mhz & 2 Mhz, It was my first UK101 mod.

[tinplatepete]

My original uk101 needed an uprated PSU because of all the modifications, 32k Ram Board, J1 Buffer board, Premier Sound VIA Card, Premier Floppy controller card, switchable 16/32 Line Display, 1Mhz/2Mhz speed, Premier Sprite/Colour Board, Premier Basic 5, Premier Basic X, Premier Toolkit, All the original Roms were mounted on an Premier EPROM extension board.

The Dos for the FCC was ROMDOS.

With all these mods it was never a reliable machine but I had a lot of fun building the boards and was a constant job keeping it going but enjoyable.

The original machine has long since gone but some of the parts from it are on my replacement UK101, 32k Ram board and some of the EPROMS.

If anyone is interested I will post a picture of the original UK101 with all the mods.

[tinplatepete]

This is my long lost upgraded uk101.

[flaxcottage]

That looks amazing!

What are all the bits? Please tell.

[tinplatepete]

The board in the middle is a switchable 1K/2K screen Ram made by Taqwa and this is one I am looking to recreate.
The board middle left is an extension EPROM board made by Premier Publications and this is also one that I will be recreating.
The board on the left hand side tight against the case is a programmable colour/sprite board also made by Premier Publications.
The board connected to the J1 socket is a J1 buffer board made by Premier Publications.
The long board on the right hand side up tight against the case is a J1 mother board by Premier Publications.
The two boards connected to the J1 extension board are as follows top Premier Publications Sound/VIA and below is a Premier Publications Floppy Disk Controller; I would love to recreate both of these boards.
The board that has the 6502 processor mounted on it is a 32K Ram board made by Audio Computers and I still have this board.
The board on its own to the right is an A to D converter made by me for interfacing the VIA board.

As you can see I was well into UK101s back in the day and enjoyed every moment of it and have recently got back into it, I now have two UK101s, one to keep original and one to upgrade, I still have some of the original Premier EPROMS and parts from my old uk101.

[flaxcottage]

In your Premier EPROMS there wouldn't happen to be a BASIC X would there? That appears to be MIA. I have the documentation and a supposedly good disassembly but it doesn't work in my UK101.

[tinplatepete]

I don't have my original Basic X, I think the Basic X you have is the one from OSIweb, this one has some modifications done to the code for it to work with other software on a Superboard, in order to get this to work on a UK101 there is a few JSRs in the code that need to be changed, I managed to work out some of the changes and got it to work but it still wasn't quite like the original Basic X, the default Sound address has been changed and it doesn't display the words Premier Basic X when first started but apart from that it works ok

By the way the original default sound address for Basic X is EF90 & EF91 (61328 & 61329 and this is located in the last few bytes of data at the end of the code in the EPROM.

I am hoping soon to have a copy of an original Premier Basic X, watch this space.

[Seldon2k]

Hardware Info Request
I have been looking at the Cassette Port of the UK101 and am a little puzzled over the selection of the Baud Rate.
The following requires a working UK101 with an unmodified cassette interface and test equipment (frequency counter or Scope).

My analysis so far goes as follows:-
An 8MHz clock divided by 8 by IC29 (7493) to give the 1MHz clock for the CPU
This gets divided by 8 in the divider chain IC59 (74163) to give C3 of 125KHz.

Now we get to the bit that requires testing, C3 goes to IC57 (74163) and in conjunction with IC58 (7400)
Then a divide by 13 (Modulo 13, resets on a count of 12), giving approx 9600Hz. This needs measuring at pin 11.
This then goes to IC63 (7474) for a divide by 2 giving 4800Hz. This can be checked at the ACIA (6850) pins 3 and 4.

The ACIA control register at its base address of F000H is, unfortunately, read-only! It must be setting the lowest two bits (CR1 & CR0) to 0 & 1.
This would result in an internal divide of 16 giving 300Hz, therefore, a Baud Rate of 300 Baud.

The reason behind this investigation is that I am attempting to add a Cassette Port to the FPGA UK101 that Grant Searle designed.
I have just read that the Baud Rate is set at 9600 in the FPGA design!
Hopefully, it can be changed by poking the control register of the emulated 6850?
I think it would be nice to relive the real experience of loading a few programs from Cassette.
I may just use an arduino/pic between the FPGA and the cassette to buffer and retransmit serialy to the FPGA board.

Hope someone can be of help,
Terry (Seldon2k)

[BigEd]

I haven't measured, but that sounds right to me. The UK101 design is a near-copy of the OSI 600 Superboard design, and the cassette interface is meant to conform to the Kansas City standard - that's 300 baud, and a specific modulation.

Although 300 baud is also a standard for serial communication, it's a bit slow, and many systems default to 9600. This is probably why Grant went for 9600 in the FPGA UK101. (In fact, he says "Since I was going to use serial only (not cassette) I increased the baud rate to a more useable 9600 baud with HARDWARE handshaking to prevent loss of data.")

Grant also indicates two lines in the VHDL to change if you want 300 baud:

Code: Select all

-- if serialClkCount < 10416 then -- 300 baud
        if serialClkCount < 325 then -- 9600 baud
[snip]
-- if serialClkCount < 5208 then -- 300 baud
        if serialClkCount < 162 then -- 9600 baud

Edit: It's a nice idea to be able to poke the ACIA to change the rate. The original chip has a divider for /16 and /64 operation, but not for /32. Grant's model doesn't have the divider. So that would be a change, and a novel one, but presumably not too tricky for someone skilled in the art.

[Seldon2k]

Thanks Ed,

I don't know how I missed that, but I am still interested in the clk going to the ACIA in the original UK101
and also if the real TX/RX Clk is present on any of the pins of the FPGA board (far less likely).

Terry (Seldon2k)

[Seldon2k]

I will post the following advert to both the Hardware and Software UK101 Archives as it seems to cover both

The next advert is the one that caused me to send off a cheque for a UK101 kit in the Summer of 1979.

Hopefully, this will be of interest.
Terry (Seldon2k)

[flaxcottage]

The next advert is the one that caused me to send off a cheque for a UK101 kit in the Summer of 1979.

Terry (Seldon2k)

Same here! That was a lot of money back in 1979.

[jonb]

I saw that advert or one very similar to it but as an impoverished teenager I could only gaze at it (rather wistfully). I remember thinking at the time that it represented to best price / performance ratio on the market that I'd seen to date.

Meanwhile, my best mate was shopping around for a computer and had considered the Newbury NewBrain (we went to Newbury to see it) and the then forthcoming Sinclair QL (which he wisely rejected as it was vapourware at the time). Around the same time the BBC Micro was announced so he waited and got one of them. Envious, me...?

[tinplatepete]

Finally found time to upload this, as promised an original unmodified copy Premier Publications BASIC X addressed 9800, I need to thank fellow UK101 owner Andy for letting me have a copy of this also letting me upload it.

Premier Publications produced BASIC X back in the 80s to link in with their Sound VIA board giving direct Sound and Printer commands; this massively speeded up any BASIC programs using sound written in BASIC X and made printing easy. The sound commands are compatible with any sound board using the AY-3-8910 or A-3-8912 series sound chip by simply telling BASIC X the address of your sound card using the Sound Address command, the only BASIC X sound command that will not work with a non-Premier Sound Board is RESET.

Unfortunately BASIC X is not compatible with a sound board using AY-3-8910 driven by a PIA chip.

BASIC X also has other commands built in for DATA storage on Cassette Tape, VIA Commands a few other new BASIC words.

Instructions for BASIC X are available on this site from flaxcottage.

[Pernod]

Finally found time to upload this, as promised an original unmodified copy Premier Publications BASIC X addressed 9800, I need to thank fellow UK101 owner Andy for letting me have a copy of this also letting me upload it.

Thanks

[flaxcottage]

Brilliant, thenks, Pete.

[tinplatepete]

I have just carried out the display modification “No Snow” by Ian B to my UK101, I have done this many times back in the day and a few recently but never the recorded the difference before and after the work was done, I tend to not solder the jumper wires on to the IC legs but cut the tracks under the main PCB and install all five jumper wires underneath, from the top it looks like nothing has changed.

I tend to only do this modification to UK101s that have already had other mods done to them, so I don’t mind cutting more tracks.

To show the effect I have used Ian`s original test program.

Looking back at some of the posts about this modification there does seem to be a problem with running at 2 MHz, I have to be honest most of the machines I have converted are only running at 1 MHz, my original UK101 back in the 80s was switchable from 1 to 2 MHz and worked perfectly OK with this modification.

A big thanks goes to Ian B for getting this modification published back in the 80s, it was the first mod I ever done to my UK101 and I still am very pleased with the results with a much improved display.

[jscrane]

Hello everyone,
Looks like I'm a bit late to this party but I thought I'd share some of the modifications I made to my Compukit back in the early 80s:

• Switching between ROM and EPROM monitors using a DPDT switch between W6 and W7 and piggybacking the chips
• Switchable 1/2 MHz by taking the processor clock from IC29 pin 8
• Switchable 300/600 baud
• 16kB RAM by piggybacking 2114s
• RS-232 interface (think this was just a matter of adding components to the board)
• 6522 VIA board
• 32x48 display modification from Swanley Electronics

The last of these was by far the most complicated. I've attached the old documentation for that here.

If you're interested, there are other manuals and documentation here: https://github.com/jscrane/UK101/tree/master/docs.

Cheers,
Steve

[uk101fan]

Hi,

Does anyone have any info on the Audio Computers RC-S 32 (Issue 2) memory board from 1981?
It has 32k of 4116 chips, needs a 12v supply and plugs into the CPU socket.

I have one, but not tried it yet. Was looking for any info before testing in my UK101.

[tinplatepete]

Hi,
I have still my original audio computers 32k card from the 80s. When I installed it back then I had to change the CPU socket as the pins on the memory card where to large for the original socket and damaged it, this caused intermittent locking up of the UK101, once I replaced the socket these issues disappeared.
As you mentioned the RAM card goes directly into the CPU socket and you will need an additional 12v feed. Also, you will need to remove the onboard 8K RAM.
You will notice that the UK101 will take slightly longer to start up while it counts the RAM.
Pete

[uk101fan]

Thanks for the info Pete,
I had assumed it could be used with the onboard RAM installed as my UK101 came with both the onboard and card ram slots populated.
Neil.