Posted: Sun Jun 29, 2014 2:49 pm
How about PLL jitter?
Sega Megadrive/Genesis development
https://gendev.spritesmind.net/forum/
https://gendev.spritesmind.net/forum/viewtopic.php?f=2&t=1792
As I've mentioned before, SDRAM is optimised for throughput, not latency. Achieving tight latency requirements, even those of the lowly MegaDrive, is non-trivial. It always comes down to a delicate balance between clock-speed and the timings in the SDRAM datasheet. KRIKzz too has mentioned that it is not easy to hit the MD latency requirements with SDRAM:Jorge Nuno wrote:SDRAM may not work at 53MHz? really? lol
Much of the UMDK hardware design is tightly-coupled, with decisions in one area affecting decisions in others. Several times I had to abandon promising avenues of development. It would have been great to have someone else like you to collaborate with when I first posted here asking for help, five years ago:On 2011-06-28, KRIKzz wrote:prophet36 i wonder if your memory controller enough fast for 32x? while ago i used altera DE1 for build similar thing, genesis games works fine, but 32x unfortunately not. i tried to count write/read period for 32x and looks like 32x has twice more fast r/w timings than genesis dma. my first sdram controller was too slow even for genesis dma, so any attempts to use dma was failed (just glitches on the screen instead of graphics). currently my controller enough fast for genny dma, but just bit more fast than req by dma, so if so if few Mhz down, then i will back to glitches world
...but that didn't happen. Beyond a few very helpful hints from Graz about getting into FPGA development, and a few very helpful hints from people like Chilly Willy about MD internals, and a lot of moral support from people like KanedaFr & MintyTheCat, I had to build this project entirely on my own. And that's fine, I learned a lot doing it. But right now as far as I'm concerned it works perfectly well, so I'm not too interested in re-engineering efforts. Besides, I've moved on to other unrelated projects (spacecraft engineering FTW).On 2008-12-13, prophet36 wrote:My problem is that I work full-time so I can only afford to spend a few hours per week on this thing, so I'm thinking of releasing the whole lot (Eagle schematics & layout, PAL design, firmware source etc) with an open-source licence, in the hope that someone out there is interested in contributing. So...any volunteers?