Subject: PDP-8/A questions

From: [email-masked] (Bob Smith)
Date: Mon, 21 Mar 1994 02:44:39 GMT

I have questions for 8/A Hardware/Systems Gurus (anyone who can
answer is a guru):
M8315 has a switch pack toward the finger end of the board.
What do the settings do for you? It looks like they are all wired
in.  I never worked with an 8/A with an M8315 processor, so I never
looked at the docs (KK8E is a tick faster).

M8317 (option board #2 for the /A) has two switch packs.  Same question
-what do they do/what are the "right settings"?

M8417-BE (32K Semi Memory using 4027 chips) has one switch pack.
Same question -what do the switches do/what are the "right settings"?

thanks
bob

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From: [email-masked] (Charles Lasner)
Date: 22 Mar 1994 00:31:56 GMT

>I have questions for 8/A Hardware/Systems Gurus (anyone who can

So, anyone who gives a bad answer is a bad guru :-).

>looked at the docs (KK8E is a tick faster).

I may be able to dig up the specifics, but as I remember it, the KK-8/A
CPU can have auto-restart enabled at the same addressses as the option
board (redundantly, and presumably for limited systems without the ext
memory board).  Anything else on the board besides this?

>From memory, whether the boot function is enabled at all, whether it can
boot while running (the M847 never does this in the -8/e!), and the ROM
even address for the ROM function code for booting in one set, and
restart in the other.

>Same question -what do the switches do/what are the "right settings"?

KT8A bank selections, if enabled.

>bob

cjl

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From: [email-masked] (Johnny Billquist)
Date: 24 Mar 1994 15:10:57 +0100

>I have questions for 8/A Hardware/Systems Gurus (anyone who can

:-)
Well, don't need to be a guru, just grabbed my copy of the
pdp8/a miniprocessor users manual

>looked at the docs (KK8E is a tick faster).

Switch	Function (When in the ON position)

S1-1	Start in field 7 (OFF position specifies Field 0)
S1-2	Start at address 4000
S1-3	Start at address 4000
S1-4	Start at address 2000
S1-5	Start at address 1000
S1-6	Start at address 0200
S1-7	CPU Auto Start Disabled
S1-8	ON for operating

Normally S1-7 and S1-8 is ON and all others are OFF.
Having more than one of S1-2 to S1-6 on will case CPU
malfunction even if CPU Auto Start is disabled.

>-what do they do/what are the "right settings"?

This will require some space, so hold on...

----
Auto-Restart Select Switch Settings

Restart Address		S2-2	S2-3	S2-4
0			OFF	OFF	OFF
200			OFF	ON	OFF
2000			ON	OFF	OFF
4200			ON	ON	OFF
----
Bootstrap Select Switch Settings

Program		S2-5 S2-6 S2-7 S2-8 S1-1 S1-2 S1-3	Memory Address
HI-LO RIM	ON   ON   ON   OFF  ON   ON   ON	7737
RK8-E		ON   OFF  ON   OFF  ON   OFF  ON	0024
TC08		ON   OFF  OFF  ON   OFF  ON   ON	7613
RF08/DF32D	OFF  ON   ON   ON   ON   OFF  OFF	7750
TA8-E		OFF  ON   ON   OFF  ON   OFF  OFF	4000
----
Boostrap Select Switch Settings for ROMs Labeled 158A2 and 159A2

Program		S2-5 S2-6 S2-7 S2-8 S1-1 S1-2 S1-3	Memory Address
HI LO RIM	ON   ON   ON   OFF  ON   ON   ON	7737
RK8-E		ON   OFF  ON   OFF  ON   OFF  ON	0024
RX8-E		ON   OFF  OFF  ON   OFF  ON   ON	0033
RF08		OFF  ON   OFF  ON   OFF  ON   OFF	7750
TA8-E		OFF  ON   OFF  OFF  OFF  ON   OFF	4000
----
Bootstrap/Auto-Restart Switch Settings

Feature			Start switch	S1-6	S1-7	S1-8
			or Activating
			Signal

Bootstrap Enabled and	BOOT Key	OFF	OFF	ON
Auto-Restart Disabled

Bootstrap Enabled and	BOOT Key	ON	ON	ON
Auto-Restart Enabled	or AC OK

Bootstrap Disabled and	AC OK		ON	ON	OFF
Auto-Restart Enabled

Bootstrap Enabled and	AC OK		ON	OFF	OFF
Auto-Restart Disabled

Bootstrap Enabled and	AC OK or	ON	OFF	ON
Auto-Restart Disabled	BOOT Key

Bootstrap and				OFF	OFF	OFF
Auto-Restart Disabled

						S2-1
Timeshare Enabled				OFF
Timeshare Disbaled				ON

						S1-4
Bootstrap Activated in Run or Stopped State	OFF
Bootstrap Activated in Stopped State Only	ON

Not Used					S1-5

>Same question -what do the switches do/what are the "right settings"?

I don't have the documentation for that one around here, but
I remember from the drawings that the switches are for the
starting address of the memory. I think it is in 16K increments.
To use above 32K you need the KT8-A.

Note that the autostart feature of the CPU is separate from the
autostart feature of the KM8-A (M8317).
-- 
Johnny Billquist                  || "I'm on a bus
CS student at Uppsala University  ||  on a psychedelic trip
email: [email-masked]       ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol

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From: [email-masked] (Charles Lasner)
Date: 25 Mar 1994 02:49:29 GMT

In article <[email-masked]>,

>S1-2	Start at address 4000

Isn't this one 6000?

>4200			ON	ON	OFF

This part about the restart address isn't totally true!

The organization of the 8/a ROM is 128x16 implemented out of two 256 x 4
82S126 chips.

The switch settings form a three-bit pattern of pairs of addresses less
than 16 decimal that can be specified as the starting address of the ROM
for restart purposes.  Thus, the lowest address is ROM address 000 and
the highest available is 014.  The boot addresses can be specified within
any six-bit pattern of pairs of addresses.

The contents of the ROM are PDP-8 12-bit switch register values and 4
bits of associated functions, which can be partially micro-coded.  The
four functions are Address Load, Extended Address Load, Start, and
Deposit/Increment address.

The four *usually* defined addresses are as you documented; these contain
ROM instructions such as:

0000 Address Load
0000 Extended Address Load ! Start

For field 0, change the Address Load value to 0200 or 2000 or 4200 or
whatever as necessary, and pick the proper ROM starting address that
contains the sequence you want.

But some ROM's, such as the WPS-oriented one, only support the restart at
00000, using the ROM address 000.  In such a ROM, the boot sequence
starts at ROM address 004.

cjl