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Merge branch 'master' into gh-pages

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This commit is contained in:
Jeff Parsons 2016-12-08 19:12:05 -08:00
commit 14ce0e99f8
1 changed files with 19 additions and 14 deletions
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33
modules/pdp11/lib/rk11.js
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@ -1174,21 +1174,26 @@ RK11.prototype.writeData = function(drive, iCylinder, iHead, iSector, nWords, ad
break;
}
/*
* TODO: Figure out why the WCHK commands fail during the 11/70 CPU EXERCISER diagnostic,
* TODO: Figure out why certain WCHK commands fail during the 11/70 CPU EXERCISER diagnostic,
* once the test starts reading/writing with physical addresses > 177777. I think all the
* UNIBUS address calculations are fine, so I'm at a loss to explain how a WCHK operation
* is supposed to succeed when the diagnostic itself appears to alter the memory that it
* just wrote. Is it possible that the controller buffers the data from the previous write,
* and the WCHK operation is comparing against its own buffer instead of physical memory?
* can succeed when the diagnostic itself appears to alter the memory immediately after the
* preceding WRITE operation.
*
* Turn on RK11 messages using the Debugger's "m rk11 on" command, and then take a look at
* the first RK11 operation that uses a UNIBUS address larger than 16 bits; eg:
* The following machine is already primed with the diagnostic, as well as the recommended
* breakpoints and messages:
*
* http://www.pcjs.org/devices/pdp11/machine/1170/panel/debugger/cpuexer/
*
* If you're not using that machine, turn on RK11 messages ("m rk11 on"), set a breakpoint at
* 033330 ("bp 033330") and then take a look at the first RK11 operation after that breakpoint;
* it should be the first one using a UNIBUS address larger than 16 bits:
*
* RK11: WRITE(147:1:2) 00453610--00463610 @037772
*
* Use a breakpoint to halt the machine at 037772 and then use the Debugger's "da" command
* to determine what UNIBUS address 00453610 is mapped to (make sure you specify it as a
* physical address using the % prefix):
* Use a breakpoint to halt the machine at 037772, and then use the Debugger's "da" command
* to determine where UNIBUS address 00453610 is mapped (make sure you specify it as a physical
* address using the % prefix):
*
* >> da %00453610
* 00,101,011,110,001,000 00453610
@ -1196,7 +1201,7 @@ RK11.prototype.writeData = function(drive, iCylinder, iHead, iSector, nWords, ad
* OFFSET: 1,011,110,001,000 00013610
* PHYSICAL: 0,000,000,000,000,000,000,000 00000000
*
* You can see that the starting address for the WRITE is perfectly calculated to start at
* So, you can see that the starting address for the WRITE is perfectly calculated to begin at
* physical address 0. And the "da" command indicates virtual address 0 points to the same
* memory:
*
@ -1207,10 +1212,10 @@ RK11.prototype.writeData = function(drive, iCylinder, iHead, iSector, nWords, ad
* & MMUMASK: 1,111,111,111,111,111,111,111 17777777
* = PHYSICAL: 0,000,000,000,000,000,000,000 00000000
*
* Strangely, the diagnostic is storing its RKCS command register at 001570, which is right in
* the middle of the first 2048 words of memory -- the same 2048 words that the diagnostic first
* WRITEs and then WCHKs. So obviously that value is changing between the time of the WRITE and
* the WCHK, so how can WCHK succeed?
* Strangely, the diagnostic (its interrupt handler to be exact) is updating the next RKCS command
* value at 001570, which is right in the middle of the first 2048 words of memory -- the same 2048
* words that the diagnostic is about to WRITE and then WCHK. Since that value is changing between
* the WRITE and the WCHK, how can WCHK succeed?
*
* For now, I just pretend that it does, by skipping the actual comparison.
*