Greg and Byron, Thanks for the info. Greg I was thinking about going the module route so I could use the eZ80F91 (same chip Byron is using). Sounds like I should just start getting some of the parts together, the board cost is not too bad which is nice. I know a few other people around who would probably also be interested even outside of NuttX.
--Brennan On Sat, Feb 20, 2021, 12:50 PM Gregory Nutt <spudan...@gmail.com> wrote: > Another thing that I did not get around to was implementing the driver > for SSD1963 LCD. That was a lot of my motivation. The SSD1963 has a > framebuffer memory interface so, given proper DMA, ought to perform > well. I am not sure if the eZ80F92 has the horsepower to make it work > well, however. > > On 2/20/2021 2:45 PM, Gregory Nutt wrote: > > I was in the middle of working with this with Konstantin w hen COVID > > stopped everything. > > > > We had just changed the crystal from 20MHz to 18MHz (as I recall) so > > that the RAM could run with a single wait state. I was implementing a > > bootloader that would reside on-chip. It would copy programs from > > serial to SPI FLASH. Then, at reset, it would copy the program from > > SPI FLASH to RAM and run from RAM. So, the 18MHz crystal should > > actually give better performance when running from RAM. > > > > That was almost working when worked stopped. But performance was > > awful. Too awful to be the slow chip so I think something was set up > > wrong (or maybe the SPI was just very slow. Never really dug into > > that.) The code is still set up to use the 20MHz crystal. > > > > By the way, when I say that the eZ80 is one of my favorite chips, I > > meant the eZ80F91. The stock Z20X has an eZ80F92 which is not as > > capable. It has fewer peripherals (no Ethernet for example) and, > > worst of all, no PLL. So it is limited to the crystal speed. The > > eZ80F91 usually uses something like a 4-5MHz crystal with the PLL > > configured to run at 50MHz. Given that it is SISC, that really > > performs pretty well. > > > > Knivd has a daughter board that can be used to replace the eZ80F92 > > with the faster eZ80F91: > > https://www.pcbway.com/project/member/?bmbno=4582C8E5-A4FF-44 . He > > also has z380 and Zneo daughter boards. The Zneo is supported by > > NuttX (as z16f), but the z380 is not. > > > > > > On 2/20/2021 1:34 PM, Brennan Ashton wrote: > >> I saw that Greg had started initial support for this retro computer a > >> year ago and I was curious if anyone else has experience with it. I > >> was considering doing a board run and building one for myself and > >> would be happy to build a few if there are people interested since I > >> will have to order multiple PCBs anyway. > >> > >> https://z20x.computer/ > >> > >> Greg, are you still doing anything on this? I know you have had > >> interest in the past with it. > >> > >> It looks like there has been some renewed interest in the Z80 with > >> Byron integrating the clang port. > >> > >> --Brennan >
