23 Jul
1997
23 Jul
'97
3:59 p.m.
From: Philip.Belben(a)powertech.co.uk
Subject: PET FAQ
Have to disagree with you on this one, the 'calaulator keyboard' PETs
seem to have the designation on 2001-8k or 2001-8/c (c referring to
calculator keyboard). The N designation meant [N]on Business and
[B]usiness style keyboards, both full-size, can find many sales ads and
books to refer to on that one (though if I were running a business on a
PET, I would have preferred the keyboard with the most keys...)
I think Commodore still had extras in stock (also small yeyboards &
tops), the blue screens aren't common but tere are some in later models
(kinda like finding VIC-20 keyboards in C-64 units)
I
am going by personal experience here, there were 8" diaply PETs sold
with 4.0, I saw a couple come through our school.
Hmmm, I have yet to see such an animal... But as I mentioned a few
answers back, with Commodore's thriftyness anything was possible. :)
Again, N does not mean small keyboard.
On many of the Commodore P.D. disks there is a program called 4032.C (I
think there is a .C on it...) it will bump your 8000 into a 40 columns
to run the 40 column programs on the disk.
'Programming the
PET/CBM' gave me those diagrams and you are right about
the ROM sizes... Will have to re-do that one.
I think
you're right on that... still have to research that one more.
Jim butterfield referred to it as Tiny Monitor in the First Book of
VIC, thanks for the clarification.
Hmmm I know that program works on the big screen units...
more
research!
DANG! It was such a neat plan too! Guess I'll have to forget that
question for now (until I can find an alternative diagram.)
Larry Anderson
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What about the 8200 Series? I am not sure of the
differences between this, the
8000 series and the 500/700 (B/P) series - see my post earlier this week.
I don't have ANY information on the 8200 series, I suspect that it was
not widely released (or not at all) in the U.S. The 500/700 series are
not in the PET line, those are the B-series machines and would be a
separate FAQ - IMO.
Large Keyboard
PETs (no more internal datasette drive):
PET 2001 xN (x=8,16,or 32 depending on amount or RAM it was shipped with)
- Full-size key keyboard w/PET graphic symbols imprinted on keys
I dispute
this. The 2001 xN, of which we had several at school, had the new
ROMs, the new motherboard (using 2332 ROM chips) but the small keyboard and the
built in C2N. This was the essential difference between the N and B machines. - Upgrade
ROMs
- Many steel cased, some w/molded plastic tops.
- many with clearer green on black displays
I thought all the N and B machines
had green screens - we even had one straight
2001 (old ROM) with a green screen. - Later
versions had 4.0 ROMs installed
Was this not only available as an upgrade? PET 2001 xB
(labeled as CBM, Commodore Business Machine)
- Full size xx key keyboard (no graphics symbols printed on keys)
- Upgrade ROMs (powers up in upper/lower case mode)
- Later versions had 4.0 ROMs installed
- Many w/molded plastic tops some steel cased.
Our green-screened old-ROM
machine was labelled CBM, but was again a small
keyboard/internal tape machine. Otherwise I remember little about the B
machines PET/CBM 40xx
Series (PET= N keyboard/ROM, CBM= B keyboard/ROM, xx= RAM)
I wasn't aware of a
small keyboard 4000 series. Interesting. 80 column
series (can be set to 40 column mode via software.)
Can it?!? I wasn't aware of
this. You can restrict the area in which it prints
on the screen to an arbitrary rectangle, but it doesn't behave like the
40-column machines in that the screen is still physically 80-column, it doesn't
handle wrapped text, etc. The 8200 series could be set from 80 to 40 columns by
unsoldering and moving two
chips. I haven't done this to mine yet...
Never heard of 'moving'
chips, I read it was one of the ROMs (the one
that supplies the startup values...) that determined 40 or 80 column (as
well as video RAM memory too.) I guess you mean replacing two chips,
then yes. Going back to 40 is a bit easier since you don't have to add
RAM like in the 4000 PETs.
At this point you must mention the 8296 and 8296D!
I'll have to dig up some solid info on this, as 'I said it is pretty
uncommon here.
[... SUPERPET ...]
Got one, still puzzles me,
also how much space I should devote to it as
I have only seen one (the one I bought recently). Will probably add
more as I get more time and information not very many people have asked
about them.
MOTHERBOARD
SERIES
2000 series(9" CRT) 3000 & 4000 series (8" CRT)
IEEE user tape #2 IEEE user tape #1
+------####-####--##-+ +------####-####--##-+
! # ! #!
! # ! #!
! # exp ! #! exp
! # bus ! ROMS #! bus
! # ! F E D C A B 9 #!
! # ! #!
! ! ! !
! ! ! !
! ROMS ! ! !
! F E D C A B 9 ! ! !
! ! ! !
tape # RAM MEMORY ! tape # RAM MEMORY !
#1 # ! #2 # !
+--------------------+ +--------------------+
The left hand board is a
hybrid of the original motherboard (of which there were
no fewer than _four_ versions). Remember the original motherboard used 2
kilobyte (800 Hex) ROM chips (6540s in most, 2316s in some). The ROMS were
therefore not F E D C A B 9 but F8 F0 E D8 D0 C8 C0 The righthand motherboard was the 2000B and some of the
3000 - the tape ports
were swapped on the 2000N and other 3000 AFAIK.
Will keep with Programming PET/CBMs numbering for now, I'm trying to
answer questions not confuse people more... They should suffice all my
machines except the original (of course) have the tape #2 on the inside.
8200 series: Again this basic format, but rearranged
so the separate keyboard
mod is sensible. 128k RAM on motherboard of which 96k usable (?).
Again I have no
data on the 8200 PET/CBMs, point me toward your FAQ on
it... *grin*
> WHAT ARE THE DIFFERENCES AND/OR BUGS OF MY VERSION
OF BASIC?
> Original ROMs
> Commodore had not yet implemented the IEEE-488 disk routines. Arrays are
> limited to 256 elements due to a bug in firmware. There is no machine
> language monitor nor could the PEEK command access locations above memory
> location 49152. The upper/lower case character set was inverted (SHIFT for
> lower case) (note: reading my sources there are ALOT of bugs, will take a
> while to compile them)
Some of these were not bugs but features. [so
Microsoft would have Commodore believe...]
Peeking and poking in upper memory (thresholds vary!) were disabled to stop people
looking at the ROMS. [Common among early micros fortunately Commodore learend the
'closed box means no 3rd party support' lesson early]
In the E page are some I/O addresses, so it is re-enabled from there upwards...
The only other genuine bugs I came across on my own machine (my first ever
computer was a PET - original ROMs, 13th birthday present in 1980) were one in
screen editing, and the machine crashes instead of giving the "too many files"
error.
Just skimmed a bit about bugs with the Cassette routines. There was
some usage problems on the PEEKs warning not to cluster them too close
together... Facinating stuff...
Added screen
'window' formatting control characters.
Only in 8000 series and fat 40,
AFAIK. The small screen 4000 series did not
have the new screen controller or many of the new graphics features. HOW DO I
ACCESS THE PET's M/L MONITOR?
The 'timy machine language monitor' (known as TIM to some)...
TIM stood for
Terminal Interface Monitor, according to my manual. WHAT IS THE
'KILLER POKE' AND SHOULD I WORRY ABOUT IT?.....
[ Explanation with one or
too inaccuracies has been snipped ] The old "video controller" could not be put
into a faster or a slower mode. It
was discrete TTL, and simply read the screen memory, shoved it through the
character ROM, and sent it to the monitor. It would not have affected printing
speed even if you had speeded it up.
The old PETs were slow because the SOFTWARE of the
print character routine
waited for the interval between screen scans before updating the screen memory.
This reduced conflicts over the screen RAM which would have resulted in random
pixels (snow) being illuminated on the screen. There was an input on one of the
I/O chips which was hooked up to the video circuitry and told the routine when
to access the video RAM.
The famous poke was actually to another register of the
I/O chip, and configured
this input as an output. The older pets didn't mind (much!), and the print
character routine saw the screen as always available, but on the later ones with
the new video controller, this conflicted with another output and caused the
video controller chip to do a wobbly (and could even have burnt out one or the
other).
Will re-work that one, thanks for the description.
IF PEEK(50000)
THEN POKE 59458,PEEK(59458)OR 32
NO!!!!!! Peek(50000) will only be zero on the
original old ROM pets! CAN I HOOK UP
AN EXTERNAL MONITOR TO MY PET?
With the help of the following circuit you can get a composite singnal from
the user port...
Insert Video Diagram here....
Don't use the one published in "The PET
Revealed" by Nick Hampshire. It doesn't
work.
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