Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!iuvax!cica!tut.cis.ohio-state.edu!pt.cs.cmu.edu!andrew.cmu.edu!mr2w+ From: mr2w+@andrew.cmu.edu (Michael F. Riccio) Newsgroups: comp.sys.ti Subject: Re: Addressable memory Message-ID: Date: 20 Jul 89 16:04:54 GMT References: <4752@psuvax1.cs.psu.edu> <1643@csm9a.UUCP> <176@zip.eecs.umich.edu> <8958@chinet.chi.il.us> <1664@csm9a.UUCP> <8998@chinet.chi.il.us>, <12297@pur-ee.UUCP> Distribution: na Organization: Mathematics, Carnegie Mellon, Pittsburgh, PA Lines: 80 In-Reply-To: <12297@pur-ee.UUCP> > Excerpts from ext.nn.comp.sys.ti: 20-Jul-89 Re: Addressable memory Mike > Young@pur-ee.UUCP (1058) > In article <8998@chinet.chi.il.us> edlee@chinet.chi.il.us (Edward Lee) > writes: > > The TI Extended BASIC cartridge version 1.10 has around 38KB of > firmware in > >it, but 38KB is an unusual size for computer memories. So, I suspect > that the > >TI Extended BASIC cartridge bank-switches firmware to the > >8KB (? It's been a while) area of CPU RAM reserved for cartridge > >memory as it is needed. I believe the same for the Tunnels of Doom > >cartridge. Someone please correct me if I am wrong about these > >particulars. Paul Charlton? > > > How about: > 3 GROMs @ 6k = 18k > 1 16k ROM = 16k > 1 4K RAM = 4k > ______ > 38k > ( this is only a slightly educated guess, based on the examination > of other TI cartridges. Your mileage may vary. ) Note there's no need for > bank switching here. The generic TI peripherals and firmware know nothing > about paging, banking, swapping, etc., as far as I've been able to > determine. > > > >-Ed L > >edlee@chinet.chi.il.us > Mike Young > Purdue Univ. EE Dept. > young@ecn.purdue.edu > ...!pur-ee!young Try: 4 GROMS (@6K each) 24K 12K ROM 12K --- 36K They lied about the other 2K. The 12K of ROM fits in the 8K space from >6000 to >7FFF. This is accomplished by bank switching the lower 4K (>7000 - >7FFF). Most Atari carts also have 16K of ROM and bank switch the entire 8K. The back switching is accomplished by writing to the ROM. Writing to >6000, >6004, >6008, etc pages in bank 0, and writing to >6002, >6006, >600A, etc pages in back 1. This is all described in great detail in the manual that comes with the Gram Kracker. Just FYI, here is the 4A memory map: >0000 - >1FFF (8K) ROM Op-Sys (GPL Interpreter, Math libraries, etc) >2000 - >3FFF (8K) RAM Memory Expansion >4000 - >5FFF (8K) Peripheral ROM (DSR device drivers, mapped in as needed.) >6000 - >7FFF (8K) Cartridge ROM (or RAM) >8000 - >82FF (.75K) Not used >8300 - >83FF (.25K) Scratchpad RAM (0 wait state) >8400 - >9FFF (7K) Memory Mapped I/O (Not real memory - ports) >A000 - >FFFF (24K) RAM Memory Expansion 64K total directly accessible memory. Through the memory mapped I/O, you can address 8 banks of 64K of GROM, 16K Video RAM, speech, and sound. Through the 4Kbits of CRU, you can map in unlimited banks of DSR ROM and/or RAM. Mike Riccio Com-Link Enterprises mr2w+comlink@andrew.cmu.edu ...!harvard!andrew.cmu.edu!mr2w+comlink