<html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"></head><body >Dumb thought, but just curious,<div><br></div><div>In a lot of articles about the odo10, they talh about the mmu they wanted and never got. Has anyone modified the simh emulater to create what they wanted? You could desigb in any other hardware you dreamed of as well. So, has anyone ever designed their dream machine ... not limiting it to the pso10?</div><br><br><br>-------- Original message --------<br>From Will Senn <will.senn@gmail.com> <br>Date: 12/26/2015 5:50 PM (GMT-07:00) <br>To simh@trailing-edge.com <br>Subject Re: [Simh] RK Word Count register question <br> <br><br>On 12/26/15 4:26 PM, Johnny Billquist wrote:<br>> On 2015-12-26 22:56, Johnny Billquist wrote:<br>>> Short, obvious question. Is simh expecting 16-bit addresses, and running<br>>> all addresses through the mmu in the command mode, or does it actually<br>>> use 18-, or 22-bit addresses, in which case you commands are accessing<br>>> memory, and not the I/O page, which is actually 17 777 777 410, if we<br>>> talk 22-bits.<br>><br>> Doh! Too many bits in there. 22 bit address should be 17 777 410 of <br>> course. :-)<br>><br>> Johnny<br>Johnny,<br><br>Well. You were right (and others offline) about the address needing to <br>be 17777410:<br><br>PDP-11 simulator V4.0-0 Beta git commit id: 0f43551d<br>sim> d 10000 012737<br>sim> d 10002 177440<br>sim> d 10004 177410<br>sim> d 10006 000000<br>sim> g 10000<br><br>HALT instruction, PC: 010010 (HALT)<br>sim> ex 17777410<br>17777410: 177440<br><br>I don't really understand what you are saying about the mmu and 18 or 22 <br>bits other than getting that there are PDP-11's with 16, 18 and 22 bit <br>memory sizes. I am guessing that the reason it's 17777410 in this case <br>is because the default machine in SimH is 22 bits and the IO space is <br>reserved in the top 4k on this machine. If I had been more specific and <br>limited SimH to a smaller memory footprint, less bits would be needed <br>(the upper 4k would be addressable with fewer bits).<br><br>Ah, well, off to read Chapter 6 - Memory Management out of the Processor <br>Handbook, again... I have to admit to barely skimming this chapter the <br>first few times through because it didn't really make any sense, without <br>context and I didn't think I needed to know. Now that it's relevant, and <br>with a bit more background, I'm sure it'll make a lot more sense and be <br>that much more interesting.<br><br>Thanks,<br><br>Will<br>_______________________________________________<br>Simh mailing list<br>Simh@trailing-edge.com<br>http://mailman.trailing-edge.com/mailman/listinfo/simh</body>