New Atom owner - trying to determine mods

discussion of games, software, hardware & emulators relating to the Acorn Atom
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sbadger
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New Atom owner - trying to determine mods

Post by sbadger » Mon Apr 30, 2018 1:43 pm

Hi there,

I've owned a beeb for >35 years and many machines in between but last week made a cheeky bid on an atom and was very pleasantly surprised to have won.

The machine as turned up and is in fair good nic. It needs a clean etc but you can tell it's been looked after.
Included were the original manual+schematics, books, spare chips of many sort plus a tape. It didint' come with a PSU but have sourced a modern 5v 2A which should come soon. I've already checked the LK6 LK7 and the machine is already set for 5v.

The machine has been modded a fair bit but am trying to work how what. I can see some piggybacked RAM chips and adding all the chipsl up I count 14K.

The bit i'm trying to work out are two switches that have been fitted to the rear of the case.

Right Switch - 3 wires
  • IC44 (SN74LS393N) pin 10 - q1?
    IC22 (6502) pin 37 - phi?
    IC44 pin 11 - q0?
Left Switch - 3 wires
  • R26
    IC44 pin 13 - CP
    R5
Any thoughts gratefully listened to!

thanks
Stewart
So many projects, so little time...

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oss003
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Re: New Atom owner - trying to determine mods

Post by oss003 » Mon Apr 30, 2018 2:47 pm

Hi Stewart,

The left switch, switches the CPU clock between the 4 or 3,58 mHz crystal.
If the left switch is at 4 mHz, the right switch, switches the CPU clock between 1 or 2 mHz.
If the left switch is at 3,58 mHz, the right switch, switches the CPU clock between 0,89 or 1,79 mHz.

After a few times switching at 3,58 mHz, it's possible to have noisefree plotting.
You have to be lucky to switch at the right moment.

Can you upload a picture of the inside of your Atom with the mods because then it's easier to determine what's modded.

Greetings
Kees

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hoglet
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Re: New Atom owner - trying to determine mods

Post by hoglet » Mon Apr 30, 2018 3:28 pm

oss003 wrote: Can you upload a picture of the inside of your Atom with the mods because then it's easier to determine what's modded.
I'm guessing it is this one:
https://www.ebay.co.uk/itm/Acorn-Atom-h ... _cvip=true

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oss003
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Re: New Atom owner - trying to determine mods

Post by oss003 » Mon Apr 30, 2018 3:38 pm

hoglet wrote:I'm guessing it is this one:
https://www.ebay.co.uk/itm/Acorn-Atom-h ... _cvip=true
Yep, it certainly looks like it.... =D>

Greetings
Kees

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sbadger
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Re: New Atom owner - trying to determine mods

Post by sbadger » Mon Apr 30, 2018 3:42 pm

That's the one yes.

Thanks you for decrypting that. Is that's like a bit of an overclock for the Atom?
I know the beeb was 2mhz, but wasn't the atom 1mhz?
So many projects, so little time...

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oss003
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Re: New Atom owner - trying to determine mods

Post by oss003 » Mon Apr 30, 2018 3:44 pm

Yes, you're right.
Most 6502 processors can run at 2 mHz but sometimes some other chips are having problems with 2 mHz like the 8255.

Greetings
Kees

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sbadger
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Re: New Atom owner - trying to determine mods

Post by sbadger » Tue May 01, 2018 7:05 pm

In an update, my new psu turned up today, a 5v 2a.
Or at least that's what I ordered (and what's on the packaging) but on examination it's actually 12v 1a... :shock:

Good job I checked (I always would :wink: ) but pretty sure if I'd blindly plugged it in my atom would have fried!

Stew
So many projects, so little time...

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sbadger
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Re: New Atom owner - trying to determine mods

Post by sbadger » Sun May 06, 2018 8:00 am

New PSU, new panel mount 5.5mm DC socket and some dry joints later... :-D


It's alive!!!...
IMG_1990.JPG
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roland
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Re: New Atom owner - trying to determine mods

Post by roland » Sun May 06, 2018 8:07 am

The display looks great =D>
If you zoom into the picture it looks like the vga connector is plugged into the wall :lol:
256K + 6502 Inside
MAN WOMAN :shock:

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Re: New Atom owner - trying to determine mods

Post by 1024MAK » Sun May 06, 2018 12:29 pm

roland wrote:The display looks great =D>
If you zoom into the picture it looks like the vga connector is plugged into the wall :lol:
Well, the Internet thing of things had to extend to the actual building eventually :lol:

@Stew - nice work, well done :D

Mark
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Re: New Atom owner - trying to determine mods

Post by sbadger » Tue May 08, 2018 3:21 pm

1024MAK wrote:
roland wrote:The display looks great =D>
If you zoom into the picture it looks like the vga connector is plugged into the wall :lol:
Well, the Internet thing of things had to extend to the actual building eventually :lol:

@Stew - nice work, well done :D

Mark
Yeah well... :oops: that's my workbench tidy!
So many projects, so little time...

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