On Wed, 2 May 2001, john/lori wrote: > > > > > > I'd go for a new motherboard as well, provided I can fit it into my C128 > > > Tower case ;-) > > Hey bogax, How about submitting our ideas? :) > > I have no objection, I think I'd like to hear them myself :) > > I'd just point out that, at this point it's all talk > (unless you've gotten a lot farther than I have) > > Presumably they all know what talk is worth. > > The idea is, basically, a baby AT form mother board to take > the chips from a C64, with the idea of moving to bigger and > better things eventually, and including some enhancements. > enhancements that would be included intially would be: > > 16 bit ISA bus > > multiple cartridge ports > > integrated expansion RAM > > seperate RAM for the VIC > > some sort of fast "serial" bus (ie something to serve the same > function as the C64 serial bus, but faster, this would be in > addition to or an enhancement of the serial bus)(Nate favors SCSI) > > bigger and better things would be stuff like: > > VIC compatible VGA (I don't envision anything as elaborate as what > Jeri's doing, I'd prefer 800x600 but I'd settle for 640x480 with > 256 colors) > > 16 bit CPU (jbev wants 65816, no doubt that would be easiest, > but I'm ambivalent. I'm not interested in getting tied to > proprietary hardware) > > Everything in programmable logic > > > So jbev, what did I leave out? I dont believe too much was left out. I'd like to add a note that an REC would be included, supporting up to 16M of its own ram. There was also speculation about different speeds of I/O devices, marked by page in a control register. This would allow a 14mhz device to share the bus with a 1mhz device without problems. The REC for example would run at a swift 14mhz. Bogax and I also covered some memory protection and opcode protection hardware, which on my end was geared mostly for the 65816's abort pin. Further wishing included a fully remapping MMU, allowing a larger (32bit in the 816's case) memory area to be mapped in, 4k at a time, to the 24bit address space of the 65816. This eliminates the concept of memory fragmentation, a common problem on the amiga and classic mac, and a potential issue on the scpu. > I'll just speculate breifly on RAM expansion (since that's what > I've been thinking about just recently). > > Initially I had thought to start with an 8 bit to 16 bit memory > mapper in discrete logic. This would be something that could > be pieced together out of junk (mostly) (stuff from a couple > of old mother boards) and fit the cartridge port on the C64 > Basically using UMAX to map in memory upto 16 meg in 256 byte > pages with a rudimentary DMA capability for swapping the bottom > 4K (mostly for zero page and the stack, probably no more than > 256 bytes at a time) Oops.. I should have read before I posted ;) > > Mapping would be done with 32K cache chips, and allow you to > map the maps ie you set up a bunch of 56K maps (64K minus > the bottom 4K and IO) and then select maps with a single byte. ..allowing you to switch memory maps (one each for up to 255 separate prcesses plus one more for the kernEl) with sub-microsecond speeds. Multitask, protect, the works. > DMA would use a single presettable 8 bit bi directional counter > that stopped on roll over. > > Initially it would only support 4 and 8 meg 72 pin simms > > Later the scheme would be integrated with a full blown REU > compatible, 16MB DMA capability (jbev wants multi gigabytes > and memory protection) and incorprated on the new mother board > (at which point DMA for swapping zero page becomes moot) muahaha >:-) > Now I'm wondering if it doesn't make more sense just to go > straight to an integrated mapper and REU style DMA controller, > in CPLDs. My thoughts. However, given Watson's repeated failures to get the CIA to fit in the larger xilinx cpld, it might be tough to fit all this in one IC. > I'm also wondering what the unused spots in the memory map > (those locations in the SRAM that correspond to the bottom > 4K and IO) could be used for. (DMA reload registers comes > to mind) Map the 4k into a shadow rom where you can load character sets to replace the onboard ROM. I've always been a fan of using the vic20 characters on my beloved 64. The c64's chars look kinda crappy and low-rez to me, while the vic20's are refined, thin, and light. > Also trying to decide how to fit in gobs of IO in the most > compatible way possible. Sadly, Commodore never intended on more than one device being in the cart port at once. > A discrete version of the mapper would take 40-50sq" of board > and a lot of soldering and wouldn't do much in the way of > usefull DMA. Any savings from using junk would be offset by > the additional cost of the board, if nothing else, but junk > is more accessable. > Plus I think you could fit in fast memory to memory DMA in the > expansion memory (eg 32 bits wide at the dotclk rate) > > Besides, Watson wants an REC done NOW ;) and NOW someone tells me. Where's the ol' boy hanging out anyway (reply in private). > bogax -jbev - This message was sent through the cbm-hackers mailing list. To unsubscribe: echo unsubscribe | mail firstname.lastname@example.org.
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