6 Jan
2002
6 Jan
'02
7:33 a.m.
On Jan 6, 11:26, Jerome Fine wrote:
(a) My experience with upgrading the backplane is VERY
satisfactory. It
was done by someone with sufficient skills with a soldering iron. And
yes,
wire-wrap wire was used. The specific model was the
VT103 which was
a 4 * quad backplane, i.e. 4 quad boards or 8 dual boards. And
terminating
resistors did not seem to be needed - perhaps because
of so few boards.
Many of the QBus processors have a set of terminators on the CPU card, and
the QBus spec allows for the use of short bus length with light loads and
no extra terminators. The definitions of "short" and "light" are
subject
to variation at short notice :-)
(b) With regard to the use of the M8044 and M8045
memory boards, at
one time I did that mod as well - using only 4096 bytes for the IOPAGE
addresses (from 170000 to 177776). However, if I remember correctly
(perhaps Megan can help with this aspect), it ONLY worked with either
the RT11SJ or RT11FB monitors - i.e. UNMAPPED. As soon as I
use the 11/23 board WITH the MMU activated, the MMU hardware under
RT11XM forced the full 8192 bytes of the IOPAGE to be used - there
was no other option. In addition, with the 11/73, it was NOT possible to
use a 4096 Byte IOPAGE AT ALL
This sounds familiar. And to be honest, if you are running anything other
than RT11SJ, you probably have a lot more than 28KW of memory anyway, so
the saving is minimal. My advice would be not to bother trying to squeeze
another 2KW out of the system.
--
Pete Peter Turnbull
Network Manager
University of York
6 Jan
6 Jan
8:52 a.m.
On Sun, 6 Jan 2002, Pete Turnbull wrote:
Many of the QBus processors have a set of terminators
on the CPU card, and
the QBus spec allows for the use of short bus length with light loads and
no extra terminators. The definitions of "short" and "light" are
subject
to variation at short notice :-)
I guess this explains why my system has no BDV11 board in it. Although it
doesn't completely work either.
This sounds familiar. And to be honest, if you are
running anything other
than RT11SJ, you probably have a lot more than 28KW of memory anyway, so
the saving is minimal. My advice would be not to bother trying to squeeze
another 2KW out of the system.
I'm running RT11XM, and it doesn't seem like I need an extra 2KW.
7 Jan
7 Jan
2:11 a.m.
Tom Leffingwell wrote:
On Sun, 6 Jan
2002, Pete Turnbull wrote:
Many of the QBus processors have a set of terminators on the CPU card, and
the QBus spec allows for the use of short bus length with light loads and
no extra terminators. The definitions of "short" and "light" are
subject
to variation at short notice :-)
I guess this explains why my system has no BDV11
board in it. Although it
doesn't completely work either. This sounds
familiar. And to be honest, if you are running anything other
than RT11SJ, you probably have a lot more than 28KW of memory anyway, so
the saving is minimal. My advice would be not to bother trying to squeeze
another 2KW out of the system.
I'm running RT11XM, and it doesn't seem
like I need an extra 2KW. from 20000 to 177776 (56 KBytes) to be set up in
extended memory
while still keeping PAR0 in the normal physical space from 00000 to
17776.
This restriction is essential when an ISR (Interrupt Service Routine) is
required. Otherwise, if the program uses memory in the normal manner
(MACRO.SAV is a good example), the use of VBGEXE automatically
sets the program up COMPLETELY in extended memory and makes
all 64 KBytes available for code and especially data or tables. And
providing sufficient additional extended memory is available, more extended
memory can still be used as well - although the two are rarely combined since
once a program starts to use extended memory, it usually does everything
for itself.
Note that VBGEXE probably can't be used in RT11XM when the program
uses VIRTUAL arrays since I seem to remember that one of the upper PARs
is required. So there are some limitations.
Sincerely yours,
Jerome Fine
9:30 a.m.
I'm sure whether it does or not, although I do sort of remember the
limited documentation implying it, but looking back through it can't find
it.
On Mon, 7 Jan 2002, Jerome Fine wrote:
Do you know if the application programs are using
extended memory?
If so, they gain much more than they loose, especially if they IOPAGE is
not required - and even more so if they can use more than one window.
As I stated in another post, RT11XM allows the user to request all the addresses
from 20000 to 177776 (56 KBytes) to be set up in extended memory
while still keeping PAR0 in the normal physical space from 00000 to 17776.
This restriction is essential when an ISR (Interrupt Service Routine) is
required. Otherwise, if the program uses memory in the normal manner
(MACRO.SAV is a good example), the use of VBGEXE automatically
sets the program up COMPLETELY in extended memory and makes
all 64 KBytes available for code and especially data or tables. And
providing sufficient additional extended memory is available, more extended
memory can still be used as well - although the two are rarely combined since
once a program starts to use extended memory, it usually does everything
for itself.
Note that VBGEXE probably can't be used in RT11XM when the program
uses VIRTUAL arrays since I seem to remember that one of the upper PARs
is required. So there are some limitations.
Sincerely yours,
Jerome Fine
6 Jan
6 Jan
8:58 a.m.
New subject: PDP-11 DRV11-B question
Does anyone have a list of the function of the switch settings on
the PDP DRV11-B / M7950 card? Also, is there an easy way to tell whether
the device is at least recognized by the system? Something like a "show
dev" on an alpha would be nice.
Also, can anyone point me to a document that gives a good overview
of the LSI-11 bus, so that I can understand what I'm doing when I change
these settings (such as base and vector settings)?
Thanks again,
Tom
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jhfine＠idirect.com -
pete＠dunnington.u-net.com -
tom＠sba.miami.edu