Robert Wilkinson wrote: > Im interested, tell us more. So...
>> 4MB memory with long SIMM. (Also 8MB one will work.) I know that port 128 switches section C, but don't know what about section D. 256 banks of 32KB each gives 8MB. Ramdisk in CPM22QED and MasterDOS. Memory banks and buffers in ZXVGS. >> ZX128 hardware emulator. Perhaps with Z80 turbo mode. Some non-contented memory, second Z80 at 3.56MHz, AY-3-8910/2, a hardware trick for #7FFD port emulation. The Z80 can have second clock (10MHz for Z80C). I think it would be possible to force both CPUs to work. Support in ZXVGS. >> DMA for better speed. Mostly for scroll the screen (3-5 times faster than LDIR). Could be used by SAMROM (JMKRBIG, JFARLDIR, JFARLDDR, JROLL, JCSBL, JRECLAIM, etc.) Also for disk operations (CPM22QED). >> ISA Muli I/O card crossing. High density floppy disk access, >> two serial and one parallel communication ports. Half capacity >> of harddisk. Interrupts with IM 2 verctors. I made such interface for ZX Spectrum. ISA slot on my SAM extention board waits for some wires. COMs are at ports &0X50..&0X57, LPTs at &0X58..&0X5B, where &0X is unit number. FDC is at &70..&77 ports. HDC at &60..&67 (no access to HI byte of harddisk data word). They generate IM2 vectors range &40..&7E, the priority is defined by table contents. (Joystick not available.) Support in CPM22QED (I have ZMP8250 terminal program now), MasterDOS "utility". >> Video interlacer to double vertical resolution. Depending on border colour in the first line of frame switches 32us delay on or off. Not tested idea. (Could give real 384 screen lines on SVGA monitors when used with and scandoubler and flicker-fixer. Quite expensive set, but possible...) Any more questions? -- Yarek.
