Interesting RK8E fault

[Guy Sotomayor Jr]

> On Dec 8, 2018, at 8:50 PM, Josh Dersch via cctalk <cctalk at classiccmp.org> wrote:
> 
> On Sat, Dec 8, 2018 at 7:24 PM Paul Anderson via cctalk <
> cctalk at classiccmp.org> wrote:
> 
>> Are you using the same pack for the 8 and the 11
>> 
> 
> I connected the drive I normally use with my 11/40 to the 8/e for testing
> to help narrow down where the fault was.
> I used a 16-sector pack in all cases.

You should be using 12 sector packs on the 11 and 16 sector packs on the 8.

I’m actually surprised the 16 sector pack worked on the 11.

TTFN - Guy

> 
> 
>> 
>> On Sat, Dec 8, 2018 at 8:54 AM Bill Degnan via cctalk <
>> cctalk at classiccmp.org>
>> wrote:
>> 
>>> On Sat, Dec 8, 2018, 1:02 AM Josh Dersch via cctalk <
>> cctalk at classiccmp.org
>>> wrote:
>>> 
>>>> On Fri, Dec 7, 2018 at 9:58 PM Josh Dersch <derschjo at gmail.com> wrote:
>>>> 
>>>>> Hi all --
>>>>> 
>>>>> Finally got all the parts together (and my act together) to actually
>>> get
>>>>> an RK05 lashed up to my PDP-8/e -- only took a decade or so :).  I
>>> fixed
>>>> a
>>>>> few problems with the RK05 and it appears to be behaving very nicely.
>>>>> 
>>>>> The RK8E controller is mostly working properly but fails
>> interestingly
>>>>> when running the formatter, and during the exerciser -- on cylinder
>> 128
>>>> and
>>>>> 192 and very infrequently on cylinder 64 it will get a cylinder
>>> mismatch
>>>>> when doing the seek.  When running the formatter during the
>>> verification
>>>>> pass, on cyls 64 and 128 if I retry the read it'll continue without
>>>> issues,
>>>>> but it's never successful on a retry on cylinder 192.  I tried
>> hooking
>>> it
>>>>> to the RK05 in my 11/40 and it exhibits the same behavior, so I'm
>>>> guessing
>>>>> the drive isn't at fault.  And the error is consistent across packs
>> (of
>>>>> which I have only two).
>>>>> 
>>>>> Apart from that fault the drive and controller seem to work fine -- I
>>>>> wrote out an OS/8 pack with Adventure on it (or at least the first
>> 191
>>>>> cylinders of it) and it works without issue.
>>>>> 
>>>>> Reading the RK8E service docs and schematics, the cylinder address
>>>> compare
>>>>> is done by reusing the CRC buffer, so I suspect the issue is in or
>>> around
>>>>> there -- the big problem is that debugging it is rather painful since
>>>> that
>>>>> logic is in the middle board of a three board set, with jumper blocks
>>> on
>>>>> top -- so bringing it out on an extender isn't an option.  I'm
>> curious
>>> if
>>>>> anyone's seen this issue or is so very familiar with the logic that
>> the
>>>>> fault is obvious.
>>>>> 
>>>>> I suspected the 7496 shift register at E14 which takes in the
>> cylinder
>>>>> address to be compared w/the header on disk, and I went ahead and
>>>> replaced
>>>>> it in the hopes that I'd get lucky, but no go.
>>>>> 
>>>>> Anyone have any advice?
>>>>> 
>>>>> Thanks,
>>>>> Josh
>>>>> 
>>>>> 
>>>> I'll add that during the format/verification the drive seeks properly
>>> (i.e.
>>>> it's not missing a step or overstepping), which I've confirmed by
>>> watching
>>>> the thing walk through the tracks with the cover off.
>>>> 
>>>> - Josh
>>>> 
>>> 
>>> Partitions as rka0 / rka1?
>>> B
>>> 
>>>> 
>>> 
>>