Date   : Wed, 07 Nov 2007 20:34:26 +0000
From   : pete@... (Pete Turnbull)
Subject: ROM / RAM boards...

On 07/11/2007 17:08, Rob wrote:
> On 07/11/2007, Jules Richardson <julesrichardsonuk@...> wrote:
>>
>> I just need the least painful route (which probably rules out the ROMEX board
>> as I really can't be bothered cutting wires and soldering to a new machine) so
>> adding some more expansion capability. I'm leaning toward the Sidewise boards
>> as one of those has all its pins bar one, unless someone thinks otherwise...

> I have no experience of the Aries offerings, but I've still got a
> sidewise board (bought new 25 years ago..) and it's definitely pretty
> simple.

> Socket 15 on the sidewise is split (optionally, set a link) into two
> 8K sockets into which you can put one or two 8K SRAM chips.  Another
> link enables writes to that socket.   ATPL chose to use the "any write
> access hits the RAM whatever the currently selected ROM" method, so
> you can just *LOAD romfile 8000  and it works.  Can be iffy with some
> protection schemes though, so there's a link to disable writes.   I
> (and most other serious users I imagine) took this out to a switch on
> the back, (along with, I think,  the 8K/16k switch, because you could
> disable a corrupt ROM by swapping out the bottom 8K!)

I agree.  The ATPL Sidewise was the Rolls Royce of sideways ROM boards. 
  I have two, and wired a switch -- actually a 3-position single-pole 
double-throw with centre-off -- so that I can have the sideways RAM 
write-protected, write-enabled, or disabled.  Being able to disable it 
is particularly useful because the RAM is normally mapped to the 
highest-priority slot.  However, on one of the boards, I just re-mapped 
it to a lower slot number.

-- 
Pete                                           Peter Turnbull
                                               Network Manager
                                               University of York