<div dir="ltr"><div class="gmail_default" style="font-family:arial,helvetica,sans-serif">I probably should add one more thing... RT11 and RSX, and in particular the DEC FTN compiler, supported thunks and overlays - i.e. larger-sized programs before UNIX did. IIRC, they needed them because by then the FTN subsystem needed overlays to run itself. So .. assuming my memory is correct, this was the reason why Fred rewrote the V7 code, and DEC pushed it out as part of the v7m release. Ken's original overlay support code was not sufficient for the DEC language tools. </div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><br></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif">I don't remember if Ultrix-11 or v7m for that matter, ultimately got the FTN compiler. That said, Paul W might remember as he did the linker work for Ultrix moving the VMS linker to Ultrix to support the 'Technical Languages Group' (TLG ). Utrix-32 certainly did get FTN I think a couple of other of the RSX and RSTS languages, but my memory of Fred's work was to support overlays in V7 so it could support it. This was all during the Unix wars inside of DEC. Fred was part of the 'Telephone Industries Group' (TIG) in MRK.</div></div><div hspace="streak-pt-mark" style="max-height:1px"><img alt="" style="width:0px;max-height:0px;overflow:hidden" src="https://mailfoogae.appspot.com/t?sender=aY2xlbWNAY2NjLmNvbQ%3D%3D&type=zerocontent&guid=efba0808-d12d-431a-84e4-570d6f95fa05"><font color="#ffffff" size="1">ᐧ</font></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Thu, Aug 3, 2023 at 6:54 PM Clem Cole <<a href="mailto:clemc@ccc.com">clemc@ccc.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr"><div dir="ltr"><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><br></div><div hspace="streak-pt-mark" style="max-height:1px"><img alt="" style="width: 0px; max-height: 0px; overflow: hidden;" src="https://mailfoogae.appspot.com/t?sender=aY2xlbWNAY2NjLmNvbQ%3D%3D&type=zerocontent&guid=ddd28b4b-782c-4464-8d0d-41241fd2f701"><font color="#ffffff" size="1">ᐧ</font></div></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><font color="#0000ff">below... [and I meant to answer the second ½ of your question before]</font></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Thu, Aug 3, 2023 at 6:09 PM Will Senn <<a href="mailto:will.senn@gmail.com" target="_blank">will.senn@gmail.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
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<div>Clem,<br>
<br>
Oh, so... Without I/D, you're stuck with 64k max per process, with
I/D, you can use 64k for I and 64k for D. </div></div></blockquote><div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><font color="#0000ff">Exactly but ... more in a minute.</font></div><br></div><div><br></div><div> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div><div>Was that it, or were
there other tricks to get even more allocated (didn't the 11 max
out at 256k)?<br></div></div></blockquote><div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><font color="#0000ff">Different issues... the MMU on the 40 class and the 45/55 allows 256K [18 bits], the MMU for the 70 class is 4M [22 bits], </font><span style="font-family:Arial,Helvetica,sans-serif"><font color="#0000ff">Unibus I/O controllers had 18 bits of address and RH70 controllers could</font> <font color="#0000ff">support 22 bits of extended addresses - see the processor and peripheral handbooks for details [or I can explain offline].</font></span></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><span style="font-family:Arial,Helvetica,sans-serif"><br></span></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><font color="#0000ff">What the PDP-11 books calls 'pages' are 64-byte segments. So the MMU is set up to allow the processor to address 64K or 64KI/64KD at the time, depending on if you have the I/D hardware, and the MMU is set up as to which 'pages' are being addressed.</font></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><font color="#0000ff"><br></font></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><font color="#0000ff">But you could overlay things ... [0405 files] with 'thunks'.</font></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><font color="#0000ff"><br></font></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><font color="#0000ff">So to allow a process (or the kernel) to have more than 64K, overlays can be loaded into memory and since the total physical space memory space is either 18 or 22 bits, if the kernel supports overlays - processes could get bigger [which is part of your first question]. </font></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><font color="#0000ff">V7 was when 0405 [text only] overlays were added. With DEC's release of v7m - Fred Cantor rewrote the overlay code and they became more general [and that would go into 2.9BSD].</font></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><font color="#0000ff"><br></font></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><font color="#0000ff">So the programmer needs to decide what you wanted to put into what overlay. For processes, the kernel can swap out segments and replace them as needed. The key is that link needs to generate near/far style calls and it can be a PITA. If you want to access a routine that is not currently mapped into memory, the 'thunk' needs to ask the OS to switch it. Great thought of what was going to be stored where.</font></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"> </div><br></div><div> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div><div>
<br>
The kernel could be compiled either with, or without separate I/D.
The only reason not to is if you didn't have more then 64k or were
there other reasons?<br></div></div></blockquote><div><span class="gmail_default" style="font-family:arial,helvetica,sans-serif"><font color="#0000ff">Well by V6, UNIX needed at least 64K of physical memory and it was really slow with anything less than 256K. For the kernel, using I/D allowed the kernel to grow more easily. By the time of trying to cram networking into it, running on anything less than an 11/44 was pretty hard.</font></span></div><div><font color="#0000ff"><br></font></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><font color="#0000ff">That said, Able made an alternate MMU called the ENABLE that allow 4M of memory on a Unibus system. It worked at a cache/bus repeater. So you set the internal MMU to point to it and then use its MMU. Very cool and a soft spot for me. </font><span style="color:rgb(0,0,255)">I ran an 11/60 [which is 40 class] with 2M of memory in Teklabs with the first Enable board.</span></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><span style="color:rgb(0,0,255)"><br></span></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><span style="color:rgb(0,0,255)">For whatever its worth, even with 4M the kernel had started to become a problem for V7 on an 11/70. Data buffers eat a lot of memory.</span></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div><div>
<br>
So, besides the kernel what apps tended to be split? If I remember
correctly, vi was one, pascal another?</div></div></blockquote><div><font color="#0000ff"><span class="gmail_default" style="font-family:arial,helvetica,sans-serif">Anything that started to get big ;-)</span> </font></div><div><font color="#0000ff"><br></font></div><div><font color="#0000ff">P<span class="gmail_default" style="font-family:arial,helvetica,sans-serif">people ran out of data space and text space from 64K fairly fast. With the 32-bit Vax, the UNIX Small is Beautiful thinking started to fall away. Rob has an excellent paper -> "cat -v considered harmful" BSD UNIX, and the Vaxen greatly fueled that. Adding features and thinking less about what functionality was really needed started to get lost [so now we have Gnu - but I digress]. Werner and the BSD 2.9 folks are to be commended for what they did with so few resources. They moved things back from the Vax by using the overlays, but if you were to have any semblance of performance, you need the overlays to stay resident so you need that full 4M of memory.</span></font></div><div><font color="#0000ff"><span class="gmail_default" style="font-family:arial,helvetica,sans-serif"><br></span></font></div><div><font color="#0000ff"><span class="gmail_default" style="font-family:arial,helvetica,sans-serif">As for this specific question first two subsystems for the 11 that ran out of text space were indeed vi and Pascal subsystems (Joy having had his hand in both, BTW). But they were hardly the only ones once the genie was out of the bottle. </span></font><span style="font-family:arial,helvetica,sans-serif;color:rgb(0,0,255)">Data space quickly became the real issue. <span class="gmail_default" style="font-family:arial,helvetica,sans-serif"> People really wanted larger heaps in particular. </span></span><span style="font-family:arial,helvetica,sans-serif;color:rgb(0,0,255)"> In fact, by the 1990s, I knew of few programs that run out of 32-bit worth of text space, but</span> <font color="#0000ff">many</font><span style="font-family:arial,helvetica,sans-serif;color:rgb(0,0,255)"> that <span class="gmail_default" style="font-family:arial,helvetica,sans-serif">started </span><span class="gmail_default" style="font-family:arial,helvetica,sans-serif">to </span>run out of 32-bits of data space<span class="gmail_default" style="font-family:arial,helvetica,sans-serif"> -> hence Alpha. But BTW: DEC took a performance hit originally, and there was a huge discussion at the time if 64-bits was really needed. </span></span></div></div>
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