7 Dec
2018
7 Dec
'18
9:58 p.m.
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
7 Dec
7 Dec
10:02 p.m.
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
8 Dec
8 Dec
6:42 a.m.
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:
Partitions as rka0 / rka1?
B
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
1:24 p.m.
Are you using the same pack for the 8 and the 11
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:
it
around
on
(i.e.
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
mismatch
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 > 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 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 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 > 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 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
8:50 p.m.
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.
- Josh
On Sat, Dec 8, 2018 at 8:54 AM Bill Degnan via cctalk <
cctalk at classiccmp.org>
wrote:
hooking
around
on
> > top -- so bringing it out on an extender isn't an option. I'm
curious
(i.e.
On Sat, Dec 8, 2018, 1:02 AM Josh Dersch via
cctalk <
cctalk at classiccmp.org
wrote:
interestingly
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 > > 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 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 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 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 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
10:33 p.m.
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:
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
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.
>
> 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
>>
>>>
>>
>
10:36 p.m.
On Sat, Dec 8, 2018 at 10:33 PM Guy Sotomayor Jr <ggs at shiresoft.com> wrote:
In all cases /pertinent to this discussion/, i.e. with the RK8E attached to
both the 11/40's RK05 and the RK05 I've restored for the 8/e.
I have 12-sector packs that I normally use with the 11/40.
- Josh
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:
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.
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.
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
>>
>>>
>>
>
10:43 p.m.
On Dec 8, 2018, at 10:36 PM, Josh Dersch <derschjo
at gmail.com> wrote:
On Sat, Dec 8, 2018 at 10:33 PM Guy Sotomayor Jr <ggs at shiresoft.com <mailto:ggs
at shiresoft.com>> wrote:
OK, just so that I understand the problem:
Do you see the problem only on the RK05 you restored for the 8/e and don?t see it on the
drives from the 11/40?
Or do you see the problem on all the drives when hooked to the 8/e and when using a 12
sector pack on the 11/40 you don?t see the problem when using any of the drives on the
11/40?
Or do you see the problem on the drive restored for the 8/e but not on the drives from the
11/40?
TTFN - Guy
On Dec 8, 2018, at 8:50 PM, Josh Dersch via
cctalk <cctalk at classiccmp.org <mailto:cctalk at classiccmp.org>> wrote:
On Sat, Dec 8, 2018 at 7:24 PM Paul Anderson via cctalk <
cctalk at classiccmp.org <mailto:cctalk at classiccmp.org>> wrote:
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.
In all cases /pertinent to this discussion/, i.e. with the RK8E attached to both the
11/40's RK05 and the RK05 I've restored for the 8/e.
I have 12-sector packs that I normally use with the 11/40. 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.
>
> On Sat, Dec 8, 2018 at 8:54 AM Bill Degnan via cctalk <
> cctalk at classiccmp.org <mailto:cctalk at classiccmp.org>>
> wrote:
>
>> On Sat, Dec 8, 2018, 1:02 AM Josh Dersch via cctalk <
> cctalk at classiccmp.org <mailto:cctalk at classiccmp.org>
>> wrote:
>>
>>> On Fri, Dec 7, 2018 at 9:58 PM Josh Dersch <derschjo at gmail.com
<mailto: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
>>
>>>
>>
>
10:49 p.m.
On Sat, Dec 8, 2018 at 10:43 PM Guy Sotomayor Jr <ggs at shiresoft.com> wrote:
On Dec 8, 2018, at 10:36 PM, Josh Dersch <derschjo at gmail.com> wrote:
On Sat, Dec 8, 2018 at 10:33 PM Guy Sotomayor Jr <ggs at shiresoft.com>
wrote:
In all cases /pertinent to this discussion/, i.e. with the RK8E attached
to both the 11/40's RK05 and the RK05 I've restored for the 8/e.
I have 12-sector packs that I normally use with the 11/40.
OK, just so that I understand the problem:
- Do you see the problem only on the RK05 you restored for the 8/e and
don?t see it on the drives from the 11/40?
- Or do you see the problem on all the drives when hooked to the 8/e
and when using a 12 sector pack on the 11/40 you don?t see the problem when
using any of the drives on the 11/40?
- Or do you see the problem on the drive restored for the 8/e but not
on the drives from the 11/40?
Just to clear this all up :) :
I have an RK8E that's exhibiting some odd behavior. Amongst other things
I've poked at, in order to help pinpoint the problem to the RK8E I ran the
formatter and exerciser using the RK8E with both the RK05 I restored for
use with the PDP-8/e *and* an RK05 I'd previously restored and which works
100% perfectly with my PDP-11/40. In both cases (i.e. with the 8/e's RK05
and the 11/40's RK05) I used 16-sector packs (because I wouldn't expect it
to work on the PDP-8/e otherwise).
The diagnostic and formatter behave identically with both drives.
Therefore: I assume the problem is with the RK8E.
If anyone has any insights into the inner workings of the RK8E (in
particular the CRC circuit, since it's used to compare the on-disk cylinder
address stored in the header with the cylinder selected by the RK8E's
address register) please let me know.
Thanks again,
Josh
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:
testing
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 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
>>
>>>
>>
>
9 Dec
9 Dec
5:47 a.m.
On Sun, Dec 9, 2018 at 6:50 AM Josh Dersch via cctalk
<cctalk at classiccmp.org> wrote:
If anyone has any insights into the inner workings of
the RK8E (in
particular the CRC circuit, since it's used to compare the on-disk cylinder
address stored in the header with the cylinder selected by the RK8E's
address register) please let me know.
I think you can ignore the actual CRC logic here. Just treat the CRC
register as a shift register. It is shifted in-sync with the data coming off
the disk, in this case the header word that contains the cylinder address.
Look at page 25 of the RK8-E engineering drawings (Oct72) on bitsavers.
It's sheet D04 (Major Registers PCB).
The header word bits (from the disk) are compared with the contents of the
the shift register one bit at a time by E24c. The output of that goes to E34b
(D input). E34b starts off clear, and remains clear while the bits agree. If
there is a difference in the bits (cylinder address is not right) then
E34b sets. The Q/ output goes low, pulling the S/ input (pin 10) low. This
forces E34b to remain set (The S/ and R/ direct inputs will override the
D input). So after all the bits have been compared, E34b is set if there was
an error.
-tony
1:58 p.m.
On Sun, Dec 9, 2018 at 5:47 AM Tony Duell <ard.p850ug1 at gmail.com> wrote:
On Sun, Dec 9, 2018 at 6:50 AM Josh Dersch via cctalk
<cctalk at classiccmp.org> wrote:
Thanks -- that's kind of what I'd gathered from looking at the schematics
and reading the service docs, but I wasn't 100% sure.
If anyone has any insights into the inner
workings of the RK8E (in
particular the CRC circuit, since it's used to compare the on-disk
cylinder
address stored in the header with the cylinder
selected by the RK8E's
address register) please let me know.
I think you can ignore the actual CRC logic here. Just treat the CRC
register as a shift register. It is shifted in-sync with the data coming
off
the disk, in this case the header word that contains the cylinder address.
Look at page 25 of the RK8-E engineering drawings (Oct72) on bitsavers.
It's sheet D04 (Major Registers PCB).
The header word bits (from the disk) are compared with the contents of the
the shift register one bit at a time by E24c. The output of that goes to
E34b
(D input). E34b starts off clear, and remains clear while the bits agree.
If
there is a difference in the bits (cylinder address is not right) then
E34b sets. The Q/ output goes low, pulling the S/ input (pin 10) low. This
forces E34b to remain set (The S/ and R/ direct inputs will override the
D input). So after all the bits have been compared, E34b is set if there
was
an error.
Thanks. So I'm trying to figure out what components in this path could
cause the behavior I'm seeing. To reiterate my original mail:
"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."
Clearly something with the two MSBs of the cylinder address is amiss. I
had made a guess that the 7496 at E14 might be at fault (some weird
crosstalk between various bits on the SETx signals perhaps) since this
takes in EXT CYL ADDRS and BDATA0 (the top two bits of the cylinder address
when loading the Disk Address Register via an IOT 67x3. I replaced it to
no effect.
It seems clear to me that the shift registers themselves are operating OK
-- otherwise I'd be seeing CRC errors fairly frequently when reading
sectors off the disk, and I'm not.
It seems that the DEC380 bus ICs (E13, E22, etc) for the BDATAx signals
that eventually get fed into the CRC shift registers must be OK or else the
actual data on the disk would end up randomly corrupted, and that's not
happening.
I'm looking for something that could only fail when only bits 6 and/or 7
(or 0 and 1 in DEC parlance) of the cylinder address are set, but I'm not
seeing anything.
Anyway, further debugging is in my future... thanks again for the input.
Thanks,
Josh
-tony
6:02 a.m.
On Sun, Dec 9, 2018 at 6:50 AM Josh Dersch via cctalk
<cctalk at classiccmp.org> wrote:
If anyone has any insights into the inner workings of
the RK8E (in
particular the CRC circuit, since it's used to compare the on-disk cylinder
address stored in the header with the cylinder selected by the RK8E's
address register) please let me know.
It's also worth reading chapter 11 in volume 3 of the PDP8/e (etc) maintenance
manual. In particular section 11.15.11.1 etc. It's page 11-92 (page
430 of the ,pdf
on bitsavers).
-tony
2205
days inactive
2206
days old
11 comments
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