UK101 Hardware Modifications Archive

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Seldon2k
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UK101 Hardware Modifications Archive

Postby Seldon2k » Wed Aug 09, 2017 7:28 pm

After creating this forum http://stardot.org.uk/forums/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 8) or just puzzle out what has been done to it before they acquired it. :?

I hope other will contribute any scans or hardware tips.

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BigEd
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Re: UK101 Hardware Modifications Archive

Postby BigEd » Wed Aug 09, 2017 8:58 pm

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.

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trev-ham
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Re: UK101 Hardware Modifications Archive

Postby trev-ham » Thu Aug 10, 2017 8:59 am

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

UK101mods.jpg

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flaxcottage
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Re: UK101 Hardware Modifications Archive

Postby flaxcottage » Thu Aug 10, 2017 7:22 pm

Love those circuit boards. :D =D> =D>

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

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. [-o<
- John

Currently running Level 4 Econet with BBC B, BBC B+ 128K, Master 128K, 4Mb A3000, 4Mb A3020, 4Mb A4000, 4Mb A5000 dual FDD; UK101; HP41CX setup; Psion 3a, 3mx and 5mx; Z88; TI-58c, TI-59 and printer

JonTr7
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Re: UK101 Hardware Modifications Archive

Postby JonTr7 » Fri Aug 11, 2017 7:07 am

Hi Trevor

I'm interested in a programmable sound generator board.

John

IanB
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Re: UK101 Hardware Modifications Archive

Postby IanB » Fri Aug 11, 2017 4:58 pm

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:

PCWpage147.jpg

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

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trev-ham
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Re: UK101 Hardware Modifications Archive

Postby trev-ham » Fri Aug 11, 2017 6:50 pm

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
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Re: UK101 Hardware Modifications Archive

Postby IanB » Fri Aug 11, 2017 7:13 pm

trev-ham wrote: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
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Re: UK101 Hardware Modifications Archive

Postby tinplatepete » Sat Oct 14, 2017 10:16 pm

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

Peter
Pete

tinplatepete
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Re: UK101 Hardware Modifications Archive

Postby tinplatepete » Sat Oct 14, 2017 10:18 pm

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

tinplatepete
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Re: UK101 Hardware Modifications Archive

Postby tinplatepete » Sat Oct 14, 2017 10:55 pm

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.
Pete


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