Ruud, my encryption projects like c64-https have severe memory constraints so the way I have solved that has been to use the REU to DMA things in and out of system RAM. I do this both for functions and for things like large precomputed mult tables. Complex flows like TLS 1.3 and Wireguard require too many functions to fit them all in RAM so the programs DMA the functions into place and DMA chunks of the multiplication tables. They precompute the tables on the fly at program start and DMA them into REU space. I have implemented this to work with things like x25519 and P-256 and P-384 NIST curves. Notably at above about 16Mhz the U64E’s REU DMA speed starts to become a bottleneck because it apparently stays fixed at 1Mhz. I am currently in the process of refactoring the main programs to use consistent zero page, crypto symbol, and REU public symbol to make everything more modular. I had done that int he libraries but not gone back to normalize things in and between the programs that consume them. So if you choose to duplicate my path on this you might consider coming up with a public symbols convention up front rather than do it the hard way like I am now. Justin > On May 19, 2026, at 06:46, ruud_at_baltissen.org wrote: > > Hallo allemaal, > > > I made up my mind and decided not to use anyone's OS as basic at all but to create one completely on my own way. The first idea is removing BASIC. At this moment I have a Kernal that still has all needed routines to load from or to save to floppy and even should be capable af handling RS232. In this specific case it also should be capable of doing this with JiffyDOS speed. > I started with removing BASIC commands like SIN, COS, TAN, etc. and after every removal I tested if the resulting Kernal still was capable of starting up with the known startup text and blinking cursor. At this moment I'm working on a routine that should output the number of available memory to screen as the original was located in the BASIC ROM. The BASIC ROM is already removed and I expect this number to be 55296. > > If that works I'm going to see if I can load a program at all from disk and, if so, if JiffyDOS will kick in as well. The main idea is to load every command from disk but keep some very basic commands, like DIR or equivalent, in ROM. At this moment I roughly 2 KB of free space. > > I have no intention to use an own file system on the various floppy drives. But I will certainly see if it is possible to implement directories in one or another way. The needed commands CD, MD and RD will be implemented in ROM, if possible. Some of you know that I'm working on my own DOS for 8080 machines, http://www.baltissen.org/newhtm/cbmdos.htm , and here I ran into the problem of having the command CD on disk: the moment I change the directory, the command isn't available anymore. This means I need either to work with something like PATH or store the essential commands in memory, like COMMAND.COM does in fact. > > An 8088 machine has the advantage that the 8088 can divide the memory in segments. In short this means roughly that a COM can be placed almost anywhere in memory and one can load more programs in memory if needed. This will be much more difficult with 6502 programs. Jumps and subroutines are absolute so relocating them in memory means either changing these addresses after the program has been loaded or another trick I don't know of yet. Any pointer to this challenge is welcome! > > What original programs should be able to run on an altered ROM? IMHO any program that doesn't rely on ROM routines with the exception of the ones using only the jump table at the end of the ROM. I kept that, it is only 117 bytes long and if really needed, I can still discard it. > > Other plans: > - creating a Kernal without JiffyDOS, thus purely based on the original V3 version. Not every one has a JiffyDOS license. > - maybe one based on EXOS V3 because that one is freely available. > - removing RS232 to increase the free ROM space if needed / just in case. > - enable RS232 again but based on using a board with 6551, 16450 or what ever. Much less ROM needed IMHO. Pointers to general available card are welcome! > > One remark: maybe I'm inventing the wheel for the zillionth time but it is also a fun project for me! > > To be continued.... > > > -- > > Kind regards / Met vriendelijke groet, Ruud Baltissen > > www.Baltissen.org > >
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