Simon Cooke wrote: > We had a prototype that ran at 12MHz with an overclocked > Z80... and discovered that you'd need to have some glue > (probably a finite state machine) in the middle that marshals > memory and IO transactions over to the internal memory. I know this. The CPU must have its own fast memory.
> Or possibly not; the Z380 (which is what I presume you're > thinking of using) has different wait-state logic, and can > hang on a half-clock if you need it to, so it might not be an > issue. I think fast SRAM will be used as base memory. All the SAM internal memory will be probably write-only with kind of FIFO buffer. The reads will be from fast shadow memory. David L wrote: >> 1. 4MB SIMM - 1/3 > Agreed. What types of Simms are u thinking off? EDO is getting > scarecer. Perhaps EDO, perhaps not. I must try. I don't expect much difference in standard simple access. I have 1MB SIMM now and I still have to find the socket for it. I have a lot of sockets for short SIMMs, but I didn't make the extention some years ago, so they seem to be useless now. And I still don't know how the original extention works. >> 2. ZX128 emul - 1/3 > Nope - not as much point. However, if you're talking about a > parallel processor...? Yes, second CPU. Probably Z80C at 3.56/10MHz. >> 4. ISA cross - 0/3 > Interesting. But not so easy getting of ISA hardware these > days You should search at the attic. This is only for things like: COMs (also internal modems), LPTs and FDC. There is also access to HDC, but you lose half of harddisk (no matter if you have 4GB anyway). >> 7. 28MHz CPU - 0/0 > Yes please - if u can master that one!! All I know now is the existence of such CPU. > You & Gordon where discussing MSX hardware not so long ago.... > there is an MSX graphics board (Gordon will know the name!) > which adds a lot of nice extra facilities.... could it be > adapted to work? Yes, I can do everything, but only with some help. How many people will have this card? Or better I should start design of new computer apart the SAM? There will be only extention board with socket for ASIC to get SAM compatibility? Justin Skists wrote: >> 3. DMA - 0/3 >> 7. 28MHz CPU - 0/0 > I vote for these two (on one board?)!!!! It would be hard to have them on one board. DMA (limited to 10MHz for Z80C family) with the 28MHz CPU will not help much. So DMA will work for memory of SAM, while the 28MHz CPU needs its own separate memory to work at full speed. And it is very likely I will make DMA as internal version. To solder over the existing Z80 or to put into the Z80 socket and under the Z80. Gordon Wallis wrote: > But, then, I don't really understand techy stuff like DMA and > ISA. In simplification DMA is hardware that copies memory faster than the CPU can, in theory 8 times. ISA is the cheapest way to get two serial serial ports and one parellel port. Also modem can be connected. Since you have ATOM and 2MB dive, other features won't be very useful for you. > Although a more direct 128K emulator sounds good, I'd prefer > some _new_ games ;-) Well, I can make only the former. :-( By the way, are there SAM versions of Doom, Worms and Mortal Combat? I have seen them on ZX128 already. The present voting is: 7. 28MHz CPU - 6/0 3. DMA - 3/1 5. Interlacer - 2/1 1. 4MB SIMM - 1/1 2. ZX128 emul - 1/1 6. Amiga HDFDD - 1/0 4. ISA cross - 0/1 Number of voters: 9 (2 votes to one thing, 1 invalid) Because the 28MHz CPU is large project that requires a lot of time to be made, I decided to finish DMA project first. From this voting, the speed is main direction and the DMA follows it. I have at home only the Z80A DMA and I try to connect it soon. To make external version I would need SAMBUS. Where can I get one from? -- Yarek.
