Date   : Mon, 13 Jul 2009 01:04:08 +0100
From   : pete@... (Pete Turnbull)
Subject: Atom Questions

On 12/07/2009 20:08, Ian Wolstenholme wrote:
> I've been playing with my Atoms.  They all work but one of them has a
> faulty 6502 and one of them I can't tune in properly to the TV.

Some Atoms are like that, especially with modern TVs.  Acorn actually 
made a "50Hz TV converter" for them.  It just corrects some of the 
timing to make it closer to the PAL standard (without adding colour, 
though).

> Just a few questions have sprung to mind:
> 
> 1. To upgrade them all to 12K RAM, I need 10 x 2114 RAM chips.  Has
> anyone got any?

You should try to get 2114L types -- that's the low-power version. 
Ordinary 2114s will draw more power than the original PSU is meant to 
deliver.  If this is for the lower text space, don't forget to add IC6.

If they've not got a full complement of RAM, do they have less than 6K 
video RAM?  If upgrading video RAM, remember to add IC30 if it's not 
there, and to remove the link that bypasses it on a basic Atom.

> 2. Has anyone got a spare 1MHz 6502 for sale?
> 3. What would happen if I put in a 2MHz (or more) 6502?

Exactly the same as if you used a 1MHz one.  The rating of the IC is the 
*maximum* clock speed you can use (the minimum on a 6502 is something 
like 100kHz).

> 4. Why does the official Acorn Atom PSU jack only fit 2 of my 4 Atoms!!??

They've been modified?

> 5. What is the correct connector for the Acorn expansion bus?  Is it a
> male or female connector?

If you mean the internal one, PL6, it's female (it has two rows of 32 
sockets) so you can plug a normal Eurocard into it.  If you mean the 
external one, PL7, it's male (two rows of 32 pins), so you can plug a 
64-way ribbon-cable DIN connector into it.  If you fit either or both, 
you also need to fit the 81LS95 (or equivalent) bus buffers.

> 6. How can I find out what optional ROMs are connected to the Atom
> without taking them out and reading them in an EPROM programmer? Is
> there an equivalent of *ROMS or *HELP?

You have to read the labels, put them in a programmer, or read the right 
bits of the address map.

> 7. Can I get colour graphics without any extra hardware?

Nope, you need the PAL colour card.  Or about 20+ ICs, a spare Eurocard, 
and lots of patience ;-)

-- 
Pete                                           Peter Turnbull
                                               Network Manager
                                               University of York