10 Mar
2015
10 Mar
'15
9:40 p.m.
Hi all
I was told that VAX-11/750 memory could also be used in an PDP-11/70 (or
maybe some other model). Is this true?
I have also read that there are three kinds of memory boards for the 11/750:
M8728: 256k byte memory array;
M8750: 1M byte memory array;
M7199: 4M byte memory array.
(As well as some third party boards.
Which one of these, if any, could be used in an 11/70?
Kind Regards,
Pontus.
10 Mar
10 Mar
10:39 p.m.
On Tue, Mar 10, 2015 at 5:40 PM, Pontus <pontus at update.uu.se> wrote:
Hi all
I was told that VAX-11/750 memory could also be used in an PDP-11/70 (or
maybe some other model). Is this true?
Somewhat...
I have also read that there are three kinds of memory
boards for the 11/750:
M8728: 256k byte memory array;
M8750: 1M byte memory array;
M7199: 4M byte memory array.
Yes. That sounds right (without looking up specific handle numbers),
depending on which memory controller you have in your 11/750. In
mine, I can handle 256K and 1MB boards. You also have to add row
wires to the backplane (I did this to upgrade a 2MB 11/750 to 8MB). I
have never had the fortune to run an 11/750 with 4MB boards (max of
14MB mixed with 1MB boards due to max physical address space of 16MB,
shared with other resources).
(As well as some third party boards.
Yes... CMI and others. I've run a couple of those. They might or
might not pass DEC diags but the OS doesn't care.
Which one of these, if any, could be used in an 11/70?
I am aware of the 256K array board working in the 11/70.
Also, the 1MB board that works in the 11/750 also works in the 11/725
and 11/730. I _think_ the 256K board should work in the 11/725 and
11/730 but since you are limited to 5 memory boards in that backplane,
1.25MB isn't enough to boot a VMS that's compatible with that CPU. So
electrically it would work, but logically, you wouldn't be able to
boot it. I suppose one could try 2x1MB+3x256KB and that might be
enough to boot an ancient VMS, but in practice, every 11/730 I've used
was crying for 5MB of physical RAM.
-ethan
11:03 p.m.
On 2015-03-10 22:40, Pontus wrote:
Hi all
I was told that VAX-11/750 memory could also be used in an PDP-11/70 (or
maybe some other model). Is this true?
Yes. :-)
I have also read that there are three kinds of memory
boards for the
11/750:
M8728: 256k byte memory array;
M8750: 1M byte memory array;
M7199: 4M byte memory array.
(As well as some third party boards.
Which one of these, if any, could be used in an 11/70?
Only the 256K ones.
Johnny
--
Johnny Billquist || "I'm on a bus
|| on a psychedelic trip
email: bqt at softjar.se || Reading murder books
pdp is alive! || tryin' to stay hip" - B. Idol
11:06 p.m.
On 2015-03-11 00:03, Johnny Billquist wrote:
On 2015-03-10 22:40, Pontus wrote:
By the way, while I'm at it.
The 4M ones can only be used if you have the right memory controller in
a 11/750 as well, and then only two of them, in the first two slots. The
rest are at most 1M cards, if I remember right.
And if you absolutely want to use 1M cards in an 11/70, ping me, and
I'll walk you through the howto. (Update have done this in the past. It
is not trivial, but it is possible.)
Johnny
--
Johnny Billquist || "I'm on a bus
|| on a psychedelic trip
email: bqt at softjar.se || Reading murder books
pdp is alive! || tryin' to stay hip" - B. Idol
Hi all
I was told that VAX-11/750 memory could also be used in an PDP-11/70 (or
maybe some other model). Is this true?
Yes. :-)
I have also read that there are three kinds of
memory boards for the
11/750:
M8728: 256k byte memory array;
M8750: 1M byte memory array;
M7199: 4M byte memory array.
(As well as some third party boards.
Which one of these, if any, could be used in an 11/70?
Only the 256K ones.
11:11 p.m.
On Tue, Mar 10, 2015 at 7:06 PM, Johnny Billquist <bqt at update.uu.se> wrote:
I have a crate of 256MB RAM on my 11/70s but I'd love to learn what it
takes to use 1MB boards (which I have a few of from 11/750s and
11/730s and 11/725s). I might decide it's too much trouble, but I'd
to know what's involved.
-ethan
> Which one
of these, if any, could be used in an 11/70?
And if you absolutely want to use 1M
cards in an 11/70, ping me, and I'll
walk you through the howto. (Update have done this in the past. It is not
trivial, but it is possible.)
11 Mar
11 Mar
3:39 p.m.
On 2015-03-11 00:11, Ethan Dicks wrote:
On Tue, Mar 10, 2015 at 7:06 PM, Johnny Billquist
<bqt at update.uu.se> wrote:
I have a crate of 256MB RAM on my 11/70s but I'd love to learn what it
takes to use 1MB boards (which I have a few of from 11/750s and
11/730s and 11/725s). I might decide it's too much trouble, but I'd
to know what's involved.
256K, not 256M, but anyway... :-)
There are several bits to it.
The MK11 only have 18 address pins on the backplane, which means it
cannot directly address larger boards. In addition, there are 16 card
select pins. One for each slot. At power on, the memory controller in
the MK11 writes to all cards in parallel, in order to initialize the ECC
bits on all cards.
The way you get 1M cards to work is that you need to tie together 4 card
select lines, so that your 1M card would appear to be four 256K cards in
the MK11.
In addition, you also need to code back from the four select lines into
the two additional address lines.
This is not so hard. Essentially we're talking about a OR of 4 lines,
and a 4-2 encoder.
Important additional detail is that you *really* want to make sure that
when all cards are select together, that is equivalent to the lowest
addressed cards.
So far for the hardware.
After you've done this, you then also needs to fix a software problem.
Like I said at the start, the MK11 initialize all the ECC of all the
cards, at initialization time. And it does this in parallel for all
cards. That means all card select lines are active together at
initialization. And then the address lines runs through address 0-256K
doing writes.
This means that the ECC for 3/4 of a 1M card will not be initialized.
The 1/4 that do get initialized, you want to be the low addresses, since
those you need before you can really do anything more. Having memory
errors for address 0 is really bad.
Once you've come this far, you need to write a short program that will
initialize the ECC of the rest of your memory. This can be done through
software, but it requires some tricks. Normal writes of memory expects
the ECC to already be correct, so you need to turn off ECC checking in
the MK11 before writing to the uninitialized memory. You can turn off
ECC checking in the MK11 by changing a CSR register, where you can set
the operation of the MK11.
However, there is a problem here. The CSR is in the MK11 box. But the
MK11 box is on the memory bus, and not on the Unibus. And the CSR
address is in I/O space.
The trick for this is to use the MMU and the Unibus map to get access to
the I/O space on the memory bus.
How this actually is done is hidden deep inside one of the technical
manuals of the 11/70, and in a rather weird form.
I can't seem to find that manual online. It's something like "11/70
memory subsystem manunal" or something similar. I (Update) have a
hardcopy of it somewhere.
But the theory of it is not so hard. You access an address in the Unibus
memory address space, using the MMU. The Unibus map then remaps this
address into an address in the I/O space. All access of memory through
the Unibus map will go to the memory bus.
Johnny
> Which
one of these, if any, could be used in an 11/70?
And if you absolutely want to use
1M cards in an 11/70, ping me, and I'll
walk you through the howto. (Update have done this in the past. It is not
trivial, but it is possible.) 
3:53 p.m.
Perhaps the Chapters 9/10/11 on Cache, MMU and Unibus Map in
KA-K1170-MG-003 are what you're thinking of (somehow ... :->)?
http://bitsavers.trailing-edge.com/pdf/dec/pdp11/1170/KA-K1170-MG-003_1170_…
On Wed, Mar 11, 2015 at 11:39 AM, Johnny Billquist <bqt at update.uu.se> wrote:
On 2015-03-11 00:11, Ethan Dicks wrote:
On Tue, Mar 10, 2015 at 7:06 PM, Johnny Billquist
<bqt at update.uu.se>
wrote:
256K, not 256M, but anyway... :-)
There are several bits to it.
The MK11 only have 18 address pins on the backplane, which means it cannot
directly address larger boards. In addition, there are 16 card select pins.
One for each slot. At power on, the memory controller in the MK11 writes to
all cards in parallel, in order to initialize the ECC bits on all cards.
The way you get 1M cards to work is that you need to tie together 4 card
select lines, so that your 1M card would appear to be four 256K cards in
the MK11.
In addition, you also need to code back from the four select lines into
the two additional address lines.
This is not so hard. Essentially we're talking about a OR of 4 lines, and
a 4-2 encoder.
Important additional detail is that you *really* want to make sure that
when all cards are select together, that is equivalent to the lowest
addressed cards.
So far for the hardware.
After you've done this, you then also needs to fix a software problem.
Like I said at the start, the MK11 initialize all the ECC of all the cards,
at initialization time. And it does this in parallel for all cards. That
means all card select lines are active together at initialization. And then
the address lines runs through address 0-256K doing writes.
This means that the ECC for 3/4 of a 1M card will not be initialized. The
1/4 that do get initialized, you want to be the low addresses, since those
you need before you can really do anything more. Having memory errors for
address 0 is really bad.
Once you've come this far, you need to write a short program that will
initialize the ECC of the rest of your memory. This can be done through
software, but it requires some tricks. Normal writes of memory expects the
ECC to already be correct, so you need to turn off ECC checking in the MK11
before writing to the uninitialized memory. You can turn off ECC checking
in the MK11 by changing a CSR register, where you can set the operation of
the MK11.
However, there is a problem here. The CSR is in the MK11 box. But the MK11
box is on the memory bus, and not on the Unibus. And the CSR address is in
I/O space.
The trick for this is to use the MMU and the Unibus map to get access to
the I/O space on the memory bus.
How this actually is done is hidden deep inside one of the technical
manuals of the 11/70, and in a rather weird form.
I can't seem to find that manual online. It's something like "11/70 memory
subsystem manunal" or something similar. I (Update) have a hardcopy of it
somewhere.
But the theory of it is not so hard. You access an address in the Unibus
memory address space, using the MMU. The Unibus map then remaps this
address into an address in the I/O space. All access of memory through the
Unibus map will go to the memory bus.
Johnny
Which one of these, if any, could be used in an
11/70?
I have a crate of 256MB RAM on my 11/70s but I'd love to learn what it
takes to use 1MB boards (which I have a few of from 11/750s and
11/730s and 11/725s). I might decide it's too much trouble, but I'd
to know what's involved.
>
And if you absolutely want to use 1M cards in an 11/70, ping me, and
I'll
walk you through the howto. (Update have done this in the past. It is not
trivial, but it is possible.)
4:37 p.m.
On 2015-03-11 16:53, Paul Birkel wrote:
Perhaps the Chapters 9/10/11 on Cache, MMU and Unibus
Map in
KA-K1170-MG-003 are what you're thinking of (somehow ... :->)?
http://bitsavers.trailing-edge.com/pdf/dec/pdp11/1170/KA-K1170-MG-003_1170_…
Nope. The manual I'm thinking of is for the memory subsystem only. And
it has a really nice/odd description on how you reach the MK11 CSR,
which is written in the form of a small adventure story. (Almost)
Johnny
On Wed, Mar 11, 2015 at 11:39 AM, Johnny Billquist <bqt at update.uu.se> wrote:
> On 2015-03-11 00:11, Ethan Dicks wrote:
>
>> On Tue, Mar 10, 2015 at 7:06 PM, Johnny Billquist <bqt at update.uu.se>
>> wrote:
>>
>>> Which one of these, if any, could be used in an 11/70?
>>>>>
>>>> And if you absolutely want to use 1M cards in an 11/70, ping me, and
>>> I'll
>>> walk you through the howto. (Update have done this in the past. It is not
>>> trivial, but it is possible.)
>>>
>>
>> I have a crate of 256MB RAM on my 11/70s but I'd love to learn what it
>> takes to use 1MB boards (which I have a few of from 11/750s and
>> 11/730s and 11/725s). I might decide it's too much trouble, but I'd
>> to know what's involved.
>>
>
> 256K, not 256M, but anyway... :-)
>
> There are several bits to it.
> The MK11 only have 18 address pins on the backplane, which means it cannot
> directly address larger boards. In addition, there are 16 card select pins.
> One for each slot. At power on, the memory controller in the MK11 writes to
> all cards in parallel, in order to initialize the ECC bits on all cards.
>
> The way you get 1M cards to work is that you need to tie together 4 card
> select lines, so that your 1M card would appear to be four 256K cards in
> the MK11.
>
> In addition, you also need to code back from the four select lines into
> the two additional address lines.
>
> This is not so hard. Essentially we're talking about a OR of 4 lines, and
> a 4-2 encoder.
>
> Important additional detail is that you *really* want to make sure that
> when all cards are select together, that is equivalent to the lowest
> addressed cards.
>
> So far for the hardware.
>
> After you've done this, you then also needs to fix a software problem.
> Like I said at the start, the MK11 initialize all the ECC of all the cards,
> at initialization time. And it does this in parallel for all cards. That
> means all card select lines are active together at initialization. And then
> the address lines runs through address 0-256K doing writes.
>
> This means that the ECC for 3/4 of a 1M card will not be initialized. The
> 1/4 that do get initialized, you want to be the low addresses, since those
> you need before you can really do anything more. Having memory errors for
> address 0 is really bad.
>
> Once you've come this far, you need to write a short program that will
> initialize the ECC of the rest of your memory. This can be done through
> software, but it requires some tricks. Normal writes of memory expects the
> ECC to already be correct, so you need to turn off ECC checking in the MK11
> before writing to the uninitialized memory. You can turn off ECC checking
> in the MK11 by changing a CSR register, where you can set the operation of
> the MK11.
> However, there is a problem here. The CSR is in the MK11 box. But the MK11
> box is on the memory bus, and not on the Unibus. And the CSR address is in
> I/O space.
> The trick for this is to use the MMU and the Unibus map to get access to
> the I/O space on the memory bus.
> How this actually is done is hidden deep inside one of the technical
> manuals of the 11/70, and in a rather weird form.
> I can't seem to find that manual online. It's something like "11/70
memory
> subsystem manunal" or something similar. I (Update) have a hardcopy of it
> somewhere.
>
> But the theory of it is not so hard. You access an address in the Unibus
> memory address space, using the MMU. The Unibus map then remaps this
> address into an address in the I/O space. All access of memory through the
> Unibus map will go to the memory bus.
>
> Johnny
>
>
6:30 p.m.
Then keep looking (please) ... and thanks for the lucid explanation.
Hadn't previously given any thought to initialization of ECC memory. Now I
know better!
On Wed, Mar 11, 2015 at 12:37 PM, Johnny Billquist <bqt at update.uu.se> wrote:
On 2015-03-11 16:53, Paul Birkel wrote:
Perhaps the Chapters 9/10/11 on Cache, MMU and
Unibus Map in
KA-K1170-MG-003 are what you're thinking of (somehow ... :->)?
http://bitsavers.trailing-edge.com/pdf/dec/pdp11/1170/
KA-K1170-MG-003_1170_Maintenance_Service_Guide_Apr88.pdf
Nope. The manual I'm thinking of is for the memory subsystem only. And it
has a really nice/odd description on how you reach the MK11 CSR, which is
written in the form of a small adventure story. (Almost)
Johnny
On Wed, Mar 11, 2015 at 11:39 AM, Johnny
Billquist <bqt at update.uu.se>
wrote:
On 2015-03-11 00:11, Ethan Dicks wrote:
>
> On Tue, Mar 10, 2015 at 7:06 PM, Johnny Billquist <bqt at update.uu.se>
>> wrote:
>>
>> Which one of these, if any, could be used in an 11/70?
>>>
>>>>
>>>>> And if you absolutely want to use 1M cards in an 11/70, ping me, and
>>>>
>>> I'll
>>> walk you through the howto. (Update have done this in the past. It is
>>> not
>>> trivial, but it is possible.)
>>>
>>>
>> I have a crate of 256MB RAM on my 11/70s but I'd love to learn what it
>> takes to use 1MB boards (which I have a few of from 11/750s and
>> 11/730s and 11/725s). I might decide it's too much trouble, but I'd
>> to know what's involved.
>>
>>
> 256K, not 256M, but anyway... :-)
>
> There are several bits to it.
> The MK11 only have 18 address pins on the backplane, which means it
> cannot
> directly address larger boards. In addition, there are 16 card select
> pins.
> One for each slot. At power on, the memory controller in the MK11 writes
> to
> all cards in parallel, in order to initialize the ECC bits on all cards.
>
> The way you get 1M cards to work is that you need to tie together 4 card
> select lines, so that your 1M card would appear to be four 256K cards in
> the MK11.
>
> In addition, you also need to code back from the four select lines into
> the two additional address lines.
>
> This is not so hard. Essentially we're talking about a OR of 4 lines, and
> a 4-2 encoder.
>
> Important additional detail is that you *really* want to make sure that
> when all cards are select together, that is equivalent to the lowest
> addressed cards.
>
> So far for the hardware.
>
> After you've done this, you then also needs to fix a software problem.
> Like I said at the start, the MK11 initialize all the ECC of all the
> cards,
> at initialization time. And it does this in parallel for all cards. That
> means all card select lines are active together at initialization. And
> then
> the address lines runs through address 0-256K doing writes.
>
> This means that the ECC for 3/4 of a 1M card will not be initialized. The
> 1/4 that do get initialized, you want to be the low addresses, since
> those
> you need before you can really do anything more. Having memory errors for
> address 0 is really bad.
>
> Once you've come this far, you need to write a short program that will
> initialize the ECC of the rest of your memory. This can be done through
> software, but it requires some tricks. Normal writes of memory expects
> the
> ECC to already be correct, so you need to turn off ECC checking in the
> MK11
> before writing to the uninitialized memory. You can turn off ECC checking
> in the MK11 by changing a CSR register, where you can set the operation
> of
> the MK11.
> However, there is a problem here. The CSR is in the MK11 box. But the
> MK11
> box is on the memory bus, and not on the Unibus. And the CSR address is
> in
> I/O space.
> The trick for this is to use the MMU and the Unibus map to get access to
> the I/O space on the memory bus.
> How this actually is done is hidden deep inside one of the technical
> manuals of the 11/70, and in a rather weird form.
> I can't seem to find that manual online. It's something like "11/70
> memory
> subsystem manunal" or something similar. I (Update) have a hardcopy of it
> somewhere.
>
> But the theory of it is not so hard. You access an address in the Unibus
> memory address space, using the MMU. The Unibus map then remaps this
> address into an address in the I/O space. All access of memory through
> the
> Unibus map will go to the memory bus.
>
> Johnny
>
>
>
5:10 p.m.
On Wed, Mar 11, 2015 at 11:39 AM, Johnny Billquist <bqt at update.uu.se> wrote:
Ah yes, as you say. 256K.
> And if you
absolutely want to use 1M cards in an 11/70, ping me
256K, not 256M, but anyway... :-) There are several bits to it.
The MK11 only have 18 address pins on the backplane, which means it cannot
directly address larger boards.
Right. That's why you have to add wires when upgrading an older
11/750. Just putting in new boards isn't enough.
In addition, there are 16 card select pins. One for
each slot.
Sure.... makes sense.
At power on, the memory controller in the MK11 writes
to
all cards in parallel, in order to initialize the ECC bits on all cards.
Ah ha! That's the not-obvious trick.
This is not so hard. Essentially we're talking
about a OR of 4 lines, and a
4-2 encoder.
Sure. This part makes sense to reverse the "fan-out" for the per-slot select.
Important additional detail is that you *really* want
to make sure that when
all cards are select together, that is equivalent to the lowest addressed
cards.
This totally makes sense in light of the initialization phase.
This means that the ECC for 3/4 of a 1M card will not
be initialized.
Once you've come this far, you need to write a short program that will
initialize the ECC of the rest of your memory... You can turn off ECC
checking in the MK11 by changing a CSR register... on the memory bus,
and not on the Unibus. And the CSR address is in I/O space...
Thank you for a very good explanation of the pitfalls. So I take it
that refresh isn't an issue then?
I'm not likely to try this since I do have enough 256K boards for my
11/70s (and I have plenty of places to stick 1M boards in VAXen), but
it's interesting to see what it takes.
Thanks!
-ethan
7:23 a.m.
On Wed, Mar 11, 2015 at 12:06:07AM +0100, Johnny Billquist wrote:
By the way, while I'm at it.
The 4M ones can only be used if you have the right memory controller
in a 11/750 as well, and then only two of them, in the first two
slots. The rest are at most 1M cards, if I remember right.
That is correct, it's pretty well described here:
http://home.claranet.nl/users/pb0aia/vax/750faq.html
Regards,
Pontus.
10 Mar
10 Mar
11:11 p.m.
On 03/11/2015 12:03 AM, Johnny Billquist wrote:
Thank you! I only have the bigger two, so I'll have no future regrets if
ship them with the 750 when it leaves me this Saturday :'(
/P
On 2015-03-10 22:40, Pontus wrote:
Hmm, it was probably you that told me in the first place :-)
Hi all
I was told that VAX-11/750 memory could also be used in an PDP-11/70 (or
maybe some other model). Is this true?
Yes. :-) I have also read that there are three kinds of
memory boards for the
11/750:
M8728: 256k byte memory array;
M8750: 1M byte memory array;
M7199: 4M byte memory array.
(As well as some third party boards.
Which one of these, if any, could be used in an 11/70?
Only the 256K ones.
4:35 p.m.
On 2015-03-11 16:44, Pontus Pihlgren wrote:
On Wed, Mar 11, 2015 at 12:03:38AM +0100, Johnny
Billquist wrote:
No. The memory in the 11/70 (and VAXen) is 32 bits wide. The other 11s
have 16-bit wide memory.
Johnny
Only the 256K ones.
A small follow-up. Can a M8728 (256K) be used in an 11/44?
4003
days inactive
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13 comments
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participants (4)
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bqt＠update.uu.se -
ethan.dicks＠gmail.com -
pbirkel＠gmail.com -
pontus＠update.uu.se