From 9bd2dcd4e4f21aeaab43097fd442f6a4baa768e5 Mon Sep 17 00:00:00 2001 From: Alan Cox Date: Fri, 13 Feb 2015 21:45:26 +0000 Subject: [PATCH] zx128: update README --- Kernel/platform-zx128/README | 23 ++++++++++++++++++++++- 1 file changed, 22 insertions(+), 1 deletion(-) diff --git a/Kernel/platform-zx128/README b/Kernel/platform-zx128/README index dd1f0f4d..c1f546f5 100644 --- a/Kernel/platform-zx128/README +++ b/Kernel/platform-zx128/README @@ -49,7 +49,6 @@ on the 128. TODO: -Write appropriate bankfixed.c routines Hook swap Swap over IDE @@ -98,3 +97,25 @@ Kernel in base 0x4000->0xFFFF (minus one screen), user in dock perhaps ? Would be tight for kernel but give 2 x 32K apps if supported relocations. Might need OS partly in cartridge ROM to make it work (certainly for 80col) + + +Other questions: + +Spectrum 48K using DivIDE or Microdrive and Interface 2 banked cartridge. +In this case the kernel ends up in the low 16K banked with video at 0x4000. +That would make data/common very tight indeed. + +Spectrum 128K with Interface 2 banked cartridges is similar to base ZX128 +but frees more pages for user apps. + +Spectrum 128K with the ZXMMC etc - in these cases we have 16K banked RAM in +low memory as well (in the 128K) as high. For the 128K it offers the option to +bank the kernel high along with the display, and run user processes in low +memory. As we can put the kernel data in a low bank it also means we can +put a small common at the top of each bank and run with nearly 64K available +to each user process (but with the copying costs on switches) + +Spectrum 48K with ZXMMC etc. In this case the screen being stuck at 0x4000 +rather limits the options beyond a ZX128 like set up but with kernel low +just as with cartridge. + -- 2.34.1