Envelope-to: craig@sbc-85.com
Delivery-date: Fri, 03 Oct 2025 06:09:12 -0500
To: craig@sbc-85.com
Subject: Reply to thread 'KitBug 64K Edition'
From: "UK Vintage Radio Repair and Restoration Discussion Forum" <no_reply@vintage-radio.net>
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Date: Fri, 03 Oct 2025 12:08:59 +0100

Dear HelloWorld,

Phil__G has just replied to a thread you have subscribed to entitled - KitBug 64K Edition - in the Vintage Computers forum of UK Vintage Radio Repair and Restoration Discussion Forum.

This thread is located at:
https://www.vintage-radio.net/forum/showthread.php?t=222671&goto=newpost

Here is the message that has just been posted:
***************
The latest KitbugPlus build is the MGH8060GAL one Craig. There are variations such as for the PICL and Ronald Dekker, but the MGH8060GAL one without the boot menu is the best place to start. 
The MGH8060GAL memory map (which is shared by the SC/MP Max II) is:
0000-07FF ROM (KitugPlus)
0800-0FFF RAM (stacks, vars, etc)
1000-1FFF ROM (NIBL-E)
2000-2FFF RAM
3000-3FFF usually ROM but can be RAM, generally used for Karens (relocated) PAGE2.SYS 
4000-7FFF RAM
8000-8FFF ROM (NIBL-E Tooit extensions)
9000-9FFF unallocated so could be RAM or ROM (GAL makes this easy)
A000-AFFF 8255 I/O  (IIRC in one GAL I reduced this wasted space)
B000-FFFF ROM (NIBL-FP)

Having 64k RAM and 64k ROM which can be interleaved at will via the GAL makes it very flexible, but there are some 'fixed' things:
Page zero has to be split so that KB+ can refer 'backwards' to RAM within the same page
There are two NIBL variants, one addressed at zero (and thus needs the high-memory version of KB+) and one addressed at 0x1000 which is the one we use mostly.
NIBL-FP is at D000-FFFF.
***************


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UK Vintage Radio Repair and Restoration Discussion Forum

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