Date   : Fri, 17 Dec 2010 02:54:53 -0000
From   : jumbos.bazzar@... (Mark Haysman)
Subject: Harddisc fakery using a microcontroller

----- Original Message ----- 
From: "Jules Richardson" <jules.richardson99@...>


> Alan Williams wrote:
>>> Is there any documentation on what exactly was different?
>>> I've got both 260s and 540s, and apart from the front badge,
>>> I can't see any differences on the main board?
>>
>> I agree.  I am not aware of any other differences.  A540 certainly
>> functions perfectly well with RISC iX.
>
> Wasn't there something funny about the memory timing needed to support the 
> 8MB
> that the R260 came with (as opposed to 4MB on the A540)? Might just be a 
> brain
> fart, but I think there may have been something about a resistor mod to 
> the
> A540 board to get it to work with that much RAM - and it *can* be done
> without, but the machine's left very picky about the RAM it'll work with 
> (to
> the extent that an unmodified 8MB A540 might sometimes boot and sometimes 
> not)

Now that's curious.....I've got a few of the 4MB RAM expansion boards, some 
Acorn, and some 3rd party (but with original Acorn MEMCs), and some of the 
A540s were very fussy about which ones they liked, and which ones they 
didn't, and would simply refuse to boot with them in a certain order, but 
move them around, and then it would boot, or occationally give a memory 
error.

Be interesting to know for sure about a mod-come-fix to the board to make it 
more RAM-friendly..?

Mark.