PET 2001

From: <(>
Date: Wed Jul 8 14:01:56 1998

Right. Lets hope my mail software (Lotus Cack-Mail) doesn't crash just
as I get near the end of this reply, as it did last time.

First, all concerned should glance at Larry A's PET faq, the address of
which he posted a few messages ago.

Pete Turnbull wrote:
> On Jul 7, 6:29, Doug Spence wrote:
>> On Mon, 6 Jul 1998, Olminkhof wrote:
>> > 8" screen
>> Or is it 9"? I can't check mine because they are both locked in my
>> father's bedroom at this hour.
> 9". All the ones I've seen were 9".

I agree with Pete, not that it makes much difference.

>> Supposedly the 2001N and 2001B came with 12" screens, but I've never seen
>> one.

No. Never. 12 inch screen on 4032 (or possibly 4016) and above only.

>> I'm looking at an old copy (don't have a recent one on file) of Jim
>> Brain's "Canonical List of Commodore Products" and notice that one of my
>> PETs doesn't match any model on the list. From this list:
>> PET 2001-4K 4kB, Chiclet Keys, Built-In Cassette, Black Trim.
>> PET 2001-8K 8kB, Chiclet Keys, Built-In Cassette, Blue Trim, 9" screen
>> PET 2001-16K 16kB, Chiclet Keys, Built-In Cassette, Blue Trim, 9" screen
>> PET 2001-32K 32kB, Chiclet Keys, Built-In Cassette, Blue Trim, 9" screen

First PETS: 2001-4 and 2001-8 (also called 4k PET and 8k PET). Blue trim,
blue-white phosphor, mangled and rebadged cassette (I can't remember whose)
that you open by lifting the lid.

Then: 2001-4 and 2001-8 get Black trim and C2N cassette deck

Then: Green screen.

Next was the ROM upgrade. Usual models were 2001-8N, 2001-16N, 2001-32N,
2001-8B, 2001-16B and 2001-32B. These had full-sized keyboards and external
C2N decks. In the UK, 2001-8N with tiny keyboard and built in C2N was
common. This was not a new motherboard in an old case - the case was a
different shape (slightly less tall). Larry has suggested that these might
be the 2001-8K, K standing for Calculator (-style keyboard) (sic).

All of these had small screens.

>> PET 2001B-8 8kB, Business Style, no Graphics on Keys, 12" screen
>> PET 2001B-16 16kB, Business Style, no Graphics on Keys, 12" screen
>> PET 2001B-32 32kB, Business Style, no Graphics on Keys, 12" screen
>> PET 2001N-8 8kB, Home Computer, Graphics on Keys, 12" screen, Num. Keys
>> PET 2001N-16 16kB, Home Computer, Graphics on Keys, 12" screen, Num. Keys
>> PET 2001N-32 32kB, Home Computer, Graphics on Keys, BASIC 4.0, Num. Keys.
>> PET 2001NT Teacher's PET. Same as 2001N, just rebadged

I've never heard of 2001NT.

AFAIK, N = Non business keyboard. The top row of keys was !"#$%^&'()
like the tiny keyboard machines - numbers were only on the number pad.

B = Business keyboard. Top row of keys was 1234567890, shift gave you
!"# etc. This meant you couldn't get some of the "graphics" characters
that came from shift-! etc.

Hence the reference to "Num. Keys" above.

> Mine is just labeled "PET 2001-8K" I think, with no 'N' or 'B' anywhere,
> but mine has a 9" screen and a full-size keyboard with graphics symbols.

Strange. Full size keyboard with graphics symbols should be 2001-8N

> I don't think Jim's list is quite correct. For a start, there were lots
> of 2001 PETs with 9" screen and the graphics keyboard, without the

Nor do I. All 2001 PETs had 9 inch screens.

> cassette-beside-the-keyboard. I've got one here. And the /B and /N series
> were called 3000's not 2001 everywhere except the USA. The 12" versions

Are you sure? I thought the 2001-8N and 2001-8B got renamed 3008 a bit

> didn't appear in the UK until later. According to my (USA) manual, the
> 2001/B (aka 3000 here) was a 9" screen too. IIRC, the 4000 was the first
> with a 12" screen, at least in the UK (USA might easily be different, of
> course), and that's borne out by my manuals. The 12" screen version was
> eventually called the 8000 series here, and had different firmware (and
> up to 96K RAM I think, bank-switched).

Um. The first with the 12 inch screen was the 8032. Different firmware
and re-done video circuitry. Later some of that was put into 4032,
making the "fat 40" Bank switched RAM made an 8096...

> One of the differences between the business and home versions (apart from
> graphics symbols on the keytops) was whether the machine powered up in
> upper- or lower-case.

Was it? That's weird!

Even weirder, though, was the lower case implementation.

Take a couple of steps back and get a wider view:

PET had two internal character codes. Screen codes and "ASCII". Screen
codes went from 0 to 127, and didn't include control codes; they then
went from 128 to 255 in "reverse field" (inverse video). Bit 6 (the 64s
bit) told you whether it was a shifted character or not.

0 to 31 were _at_, ABC...Z, [\], up arrow, left arrow. 32 to 63 were
conventional ASCII. 64 to 127 were the graphics characters you got from
shifting these.

First problem - nowhere for lower case. PET, in translating ASCII (or
PETSCII as it became known) into screen codes, didn't bother to
implement lower case. First it checked for control codes (0 to 31 and
128 to 159) and then it ANDed the ASCII code with 63 and stuck it on the
screen. Well, sort of. The ASCII codes for the shifted characters were
displaced from the unshifted ones by 128 instead of 64.

Now, lower case mode. Early PETs kept the bottom 128 ASCII codes
exactly as they were. Lower case went in the top 128 - NOT where you'd
conventionally put it (those who followed the algorithm above will have
worked out that the conventional ASCII codes for lower case would
display space, !"#$ etc.). Since lower case was implemented in the
character generator only - an I/O pin went to an address line on the
character ROM - you had to use SHIFT to get LOWER case.

And that was the second problem. Later PETS swapped lower and upper
case letters. So now ASCII codes 65 and up, which still mapped onto
screen codes 1 and up, gave LOWER case letters, but you pressed SHIFT
for upper case. However the OS and BASIC (one and the same, really)
treated unshifted as letters, and shifted as meaningless graphics
characters, whichever mode you were in.

Confused? It is, isn't it!

>> Note that at least the early PET 2001 machines came with a white display.
>> I think some of the 'newer' ones came with green phosphor instead.(?)
> My 2001-8K is white phosphor. The full-size-keyboard ones were green.

The common arrangement. But the colour change predated the ROM and
Keyboard Size changes. Just.

>> But there's a lot more to 'features' than outward appearance. The machine
>> uses a 1.0MHz 6502. It has an 80-pin memory expansion port on the right
>> side (the 40 pins on the top side are all ground). There's an external
>> cassette interface at the back, for TAPE #2.
> On the later models, that's TAPE#1 and the TAPE#2 is an internal connector.
>> There's an IEEE-488


>> interface on the back that was used for printers, disk drives, modems, and
>> probably other stuff. There's a user port on the back which is similar to
>> the user port on the VIC-20/C64.

IEEE-488 to RS232 converters were very popular here, since PET had no serial
port. Alternatively, software could be written to drive a pin on the user port
serially. I know. I've done it.

>> The original ROMs don't have a monitor or support a disk drive, but ugrade

"Don't support a disk drive" is a euphemism for so many bugs you can't
use it at all!

>> ROMs (which I think came out in 1979?) fix both of those things.

About then. The monitor - hex only - replaced diagnostic routines in
the original ROMs. A listing was actually given in the original PET
manual, but I couldn't get it to work whenever I typed it in...

>> I don't have a machine with BASIC 4.0, so I don't know how that starts

It says "COMMODORE BASIC 4.0" but I can't remember whether between *** or

>> up. Upgrade ROM machines also have a Microsoft easter egg in them
>> whcih is missing from the original ROMs.)

Indeed. Type WAIT 6502,100

> There was a very-short-lived BASIC-2, and BASIC-3 (more-or-less the upgrade
> ROM set) was around for a while before 4. 4 has extra commands for the
> disk, instead of having to use the generic IEEE channel commands, but
> otherwise it's almost the same as 3.

I have heard all sorts of numbering schemes for BASIC versions. The
only thing they agree on is 4. AFAIK, the BASIC in 3008 and friends was
identical to the upgrade ROMs that went in original PETs.

> Only the original ROMs start up with ***; all of the later ones used ###.

That clears up my mystery above. Thank you.

>> It might also be important to mention that the PET has a timer that
>> operates in real time. And it has the same character set(s) as the VIC-20
>> and C64, but you can't switch between the upper/lower-case text character
>> set and the upper-case/graphics set without issuing a POKE command. (Was
>> it 49512,12 and 49512,14? My memory is rusty.)
> All those POKEs are ROM-version-dependent.

Wrong, I'm afraid. POKE 59468, 12 (UC/graphics) and POKE 59486,14 (LC)
are INDEPENDENT of ROM version. On 8032/8096, 8296 and Fat 40 you can
use PRINT CHR$(14) and PRINT CHR$(142) (CTRL-N and CTRL-SHIFT-N except
that PET never had a control key) to change between the modes. These
codes also change to wide line spacing in LC mode, which the pokes

Hope this clears up some misconceptions.

Received on Wed Jul 08 1998 - 14:01:56 BST

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