Re: Who has Option-ROMs for the PET2001 / Basic1 ?

On Thu, Oct 1, 2020 at 3:10 PM Rhialto <rhialto_at_falu.nl> wrote:
>
> On Sun 27 Sep 2020 at 05:46:27 -0500, vossi wrote:
> > Hello,
> >
> > I'm very interested in option rom's for the pet2001.
> > I think there's not much available because the 2001 has no option rom
> > sockets!
>
> Huh? The 2001 motherboard had empty sockets for 4KB blocks at $9000,
> $A000 and $B000, from the very first model onwards...  but now that I
> think of it, there were variants of the board, with 2 different types of
> ROM and 2 different types of RAM chips... maybe the variant with the 2
> KB ROMs didn't have space for empty sockets?

PCB #320008 (the first 2001 released) has no empty ROM sockets. It
uses MPS6540 ROMs that are 2Kx8 each.
I have seen quite a few of them (and I own a 2001 with this motherboard).
There are other 2001's PCB revisions that use 2316 ROMs, I have never
seen one of these, but the schematic seems to imply they didn't have
any empty ROM socket too.
2001N have $Bxxx, $Axxx and $9xxx empty ROM sockets (or just $Axxx and
$9xxx if one installs basic 4). The 2001N PCB uses 4Kx8 ROMs with a
single 2Kx8 one at $Exxx socket.
Character ROM was always 2Kx8, but that's not addressable from the CPU
in PET machines.

Frank IZ8DWF