Geneve GPL Interpreter

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Revision as of 02:53, 17 November 2019 by Mizapf (talk | contribs) (Mapping)
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For Speed 5 and MDOS DSR:

Page for 0000-1FFF Page for 2000-3FFF Page for 4000-5FFF Page for 6000-7FFF Page for 8000-9FFF Page for A000-BFFF Page for C000-DFFF Page for E000-FFFF
EC ED 07 34 EE EF 03 35

For different speeds different kinds of RAM (DRAM vs. SRAM) are used. The ROMPAGE feature sets the 4000-5FFF page value to >BA, which points to the address space of the peripheral card in the box, unlike >07 which contains the MDOS replacement DSR.

Speed selection

The GPL Interpreter allows for selecting the execution speed. Five speeds are selectable. The speed is determined by these settings:

Speed Video waitstates Extra waitstates Page for 0000-1FFF Page for 8000-9FFF
1 x x EC 34
2 x - 33 34
3 x - EC 34
4 x - 33 EE
5 x - EC EE

The memory pages EC, ED, EE, and EF are SRAM pages with 0 waitstate access. Other pages are DRAM pages with one waitstate. Thus, the speed is controlled by waitstates in the GPL interpreter (locations 0000-1FFF) and in the PAD RAM (8300-83FF), which is not the high speed on-chip RAM of the TMS9995 processor (which is always located at F000, regardless of the mapper value).