[Simh] pdp8i vs pdp8e

[Eric Smith]

Gee Bob, so what's the hold up?

Seriously though -- _thank you_ for all your work on these...your
simulators are great!  I've had a lot of fun running the old
environments on the pdp-8, pdp-11, the vax, and some of your other
simulators.  If I had the energy I'd get something going between my
real vax and a simulated one.

Superb work, I think I can say we all love it.

Eric KD5UWL


On May 24, 2010, at 5:28 PM, Bob Supnik <bob at supnik.org> wrote:

> As the clock simulator says, it implements both the 8/E and 8/A
> instructions. It does not implement the 8/I.
>
> The PDP-8 simulator is not an "all models" system; it only supports
> the
> 8/E and 8/A.
>
> Adding model-specific behavior (for the classic 8, 8/S, 8I/L, and
> distinguishing the 8/E from the 8/A) would not be impossible, but it
> would be fairly tedious and difficult to verify.  The earlier 8's use
> different peripherals for DECtape, magtape, line printer, and clock,
> among others, so new peripheral simulators would be needed, along with
> diagnostic and test programs.
>
> /Bob
>
> On 5/24/2010 12:00 PM, simh-request at trailing-edge.com wrote:
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>> Today's Topics:
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>>    1.  pdp-8 experts? (Brad Parker)
>>
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>> ---
>> -------------------------------------------------------------------
>>
>> Message: 1
>> Date: Sun, 23 May 2010 21:14:37 -0400
>> From: Brad Parker<brad at heeltoe.com>
>> Subject: [Simh] pdp-8 experts?
>> To: simh at trailing-edge.com
>> Message-ID:<4BF9D2FD.3060903 at heeltoe.com>
>> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>>
>> Any pdp-8 experts here?
>>
>> I've been fighting a problem with tss/8 for a bit.  I've been
>> working on
>> getting it to build from sources.
>> When I build for the pdp-8/e it seems to work correctly using simh.
>> When I build for the the pdp-8/i
>> I have problems.
>>
>> My goal is a clean build from sources for the 8/i.  But the KW8/I
>> clock
>> emulation in simh is (to my mind)
>> suspect.
>>
>> I'm happy to go dig in the docs and look at the schematics, but I
>> thought I'd ask here also.  In the TSS/8
>> sources they do this for the 8/I:
>>
>>   244             IFZERO CPU<
>>   245             /KW8I           REAL TIME CLOCK
>>   246
>>   247       6137  CECI=6137                       /CLEAR AND ENABLE
>> CLOCK AND INTERRUPT
>>   248       6133  CSCF=6133                       /SKIP AND CLEAR
>> FLAG
>> IF FLAG
>>
>> Naturally, for the 8/e they say:
>>
>>   256             IFZERO CPU-2<
>>   257             CECI=6131                       /CLOCK ENABLE
>>   258             CSCF=6133                       /SKIP AND CLEAR
>> FLAG
>> IF FLAG
>>
>> When I build for the 8/I I don't get clock interrupts the way I
>> expect.
>> Looking at the clock code in
>> simh 6137 won't enable lock interrupts.  6133 will skip and clear.
>> When
>> I build for the 8/e I got
>> clock interrrupts.
>>
>> Ages ago I wrote KW8/I verilog code from the specs I could find and
>> it
>> does interpret 6137 as CECI
>> and does enable clock interrupts.
>>
>> Anyone have an opinion?
>>
>> it may be that competing clock hardware (i.e. 8/i, 8/e, 8/a) have
>> different ideas about 6137...
>>
>> -brad
>>
>>
>>
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