From: muta...@gmail.com   
      
   On Tuesday, April 4, 2023 at 8:11:04 PM UTC+8, Dan Cross wrote:   
   > In article ,   
   > muta...@gmail.com  wrote:    
   > >On Tuesday, April 4, 2023 at 7:20:02 PM UTC+8, Dan Cross wrote:    
   > >> >> >Ok, so the proposed laptop could be built, and cover both    
   > >> >> >memory-mapped I/O and "legacy IO".    
   > >> >    
   > >> >> That would be a silly design if your intent is to work with a    
   > >> >> CPU that doesn't even have programmed IO instructions, let alone    
   > >> >> the sort of external bus cycles required for PIO to work.    
   > >> >    
   > >> >The intent is to allow the user to zap either CPU type    
   > >> >onto the FPGA.    
   > >    
   > >> Now you're back to the original problem of trying to shoehorn a    
   > >> MIPS core into a system designed around an x86 core, or the    
   > >> inverse, which is what I already told you was problematic.    
   > >    
   > >That *is* the solution to the original problem. A serial    
   > >port that can be driven by either MMIO or legacy IO.    
   > >    
   > >It's not a silly design. It allows flexibility of CPU loading    
   > >onto the FPGA.   
   > >[snip]    
   >    
   > You don't seem to be aware that an x86 CPU can also use MMIO for    
   > a serial port, provided that serial port supports MMIO already.    
   > So if you have a UART that already supports MMIO, you don't    
   > _need_ the legacy port-IO based support. If you're already    
   > modifying a hobbyist OS to support MMIO access to the serial    
   > port for, say, a MIPS-like CPU core, then you can just use that    
   > same support code on x86 as well.   
      
   I think we might be talking cross-purposes.   
      
   I am talking about a general-purpose laptop (which   
   apparently hasn't been built, but may be possible to   
   be built).   
      
   General purpose meaning I can flash any CPU I want   
   on it. Or at a minimum, Plasma and 80836:   
      
   https://opencores.org/projects/zet86   
      
   I would like to own such a laptop, even though I don't   
   have an immediate use for such a machine. So that   
   if I want to run a S/370 (or modified version) in 10   
   years from now, the machine is ready, I can "just"   
   start working on the VHDL (or hire someone to do that).   
      
   If I flash an 80386 onto the FPGA, then I expect my   
   existing 80386 code to work, which uses the "out"   
   instruction.   
      
   I don't expect to be told "sorry, your laptop serial port   
   only supports mmio so you need to rewrite any software   
   that uses the 'out' instruction".   
      
   > But more generally you seem to think that the only thing that is    
   > important are driving simple devices like a UART, but there is a    
   > lot more that goes into a modern computer, particularly a device    
   > in the laptop class. Perhaps if you took some time to learn    
   > something about computer architecture this would make a little    
   > more sense to you.   
      
   I didn't say that I wanted a modern computer.   
      
   That's why I want to drive a serial port in the first place.   
      
   Other devices I want to drive are a hard disk, and I'm   
   willing to do that over serial port too. If there are other   
   options, that don't require too much coding, I'm interested   
   in them as an alternative, but at the end of the day, I'm   
   happy to drive the keyboard, terminal, modem and hard   
   disk over serial ports (which I already know how to drive   
   using "out" instructions).   
      
   Yes, I know it will be slow.   
      
   It was also slow when I used a Commodore 64 with   
   a floppy disk on serial port.   
      
   I survived.   
      
   BFN. Paul.   
      
   --- SoupGate-Win32 v1.05   
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