Date   : Wed, 18 May 2005 23:28:47 +0100 (BST)
From   : Chris Johns <chris.johns@...>
Subject: Re: RAM chips for Model B

On Wed, 18 May 2005, Jules Richardson wrote:

> Can someone confirm this with their own copy of the service manual? That
> sounds a bit iffy to me, as if Michael's machine is working when in 16K
> mode it'd imply that ICs 61 to 68 are at fault - but in 32K mode
> according to my manual it's IC's 53 to 60 that are mapped to the upper
> 16K of memory (which is right where video memory is on a 32K machine I
> believe). That almost suggests that the fault might be elsewhere rather
> than RAM; maybe in the CRTC itself or in the buffer ICs (8 and 9)
> inbetween the CRTC and memory...

If you set the link used to select 16K mode on a 32K machine to something
else, it will use the other 16K bank. It might be one way for 32K, one for
16K and off altogether for the other 16K, but I can't remember the exact
details now.

Might be worth a try to see what results that gives - or of course it
may not given any further insight.

Cheers

Chris