[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [N8VEM-S100:6623] Re: CPM3 memory banks

Hi Bob --

>> In all practicality, I think 8 banks is plenty, but using 2 x 512k static RAM chips
>> provides the possibility of 16 banks.

Maybe take a look at what I've done?  It is in the "simple MMU" section of my Web site (sites.google.com/site/oldcpusrus).  I used a 74LS670 to extend the address range of a Z80.  It is running now with CP/M 2.2 and one 512 x 8 SRAM giving 16 pages of 32k each.  BUT, I'm having second thoughts about 32k pages.  The way CP/M is structured (with the system in high memory and the base page, and TPA, in low memory) switching banks is tricky.  Maybe 16k pages would work better?  Seems ideal (to me anyway) to have the banked memory in the range of 4000h to c000h??

Anyway, my experiment is running at 10 MHz with a compact flash as "disk".  Seems very solid.  It is quite compact -- only about a dozen chips.  If only I knew how to turn it into an S100 card ......