Nasta wrote:However, both the QL stuff and QIMI code only uses the first 256 bytes (or less) at $18000..$180FF (QL) and last 256 bytes at $1BF00..$1BFFF (QIMI).
Again my point: The
text in the schematics proposes to decode using A19..A14, A10, A6, A1 in an
external QIMI. That does
not only select it for the first and the last 256 bytes!
Are you saying that
all external QIMI are
not implemented as the text proposes, but use more address lines instead?
Nasta wrote:This is well tested on both real and clone QIMIs and Aurora.
The question is,
what has been well tested? Obviously QIMI and QL internal registers do not collide. Also a few I/O registers were used in the $18000..$1FFFF area without collision, but that could have been area snippets which are not selected by the proposed equation, or just internal QIMI overidden by DSMCL.
Nasta wrote:In principle, $1C000..$1FFFF was never defined so various boards can use this as they see fit. Is there a possibility to use that area for the internal RAM/ROM of the Q68?
No, it is much too late to change that. The QL documentation defines this as "external I/O", and that's exactly what the Q68 uses it for. I could only change the Q68 extension bus connector and ethernet areas as detailed in my previous post - they are not yet used by much software. Normally I wanted to have fixed this last weekend already.
Nasta wrote:That way the $18000..1BFFF remains an IO area and can then be partially predefined amongst different systems.
The QL defines and uses this as "internal I/O". It was never meant for external devices at all. I have my doubts, now to do the opposite, and place
all new external devices right where they were never meant to be. Mind you: This is only a potential workaround for Gold Card leaving no I/O space in the "external I/O" area. It is not needed for the QL itself, the Q68, or Dave's new CPU card.
As I still have doubts about the QL internal I/O area, I tend to leave:
$1D000-$1D7FC Ethernet CP2200
$1D800-$1DFFC Q68 external extension bus connector
The worst that could happen:
If a new QL extension is made that wants to re-use Q68 drivers, and
if that QL extension requires the Gold Card, the base address in the driver software would have to be changed. As long as register offsets are the same, not a large effort.