From: William Levak (wlevak_at_sdf.lonestar.org)
Date: 2006-08-22 05:36:06
On Tue, 22 Aug 2006, Ethan Dicks wrote:
> Date: Tue, 22 Aug 2006 09:57:44 +1200
> From: Ethan Dicks <ethan.dicks@gmail.com>
> Reply-To: cbm-hackers@ling.gu.se
> To: cbm-hackers@ling.gu.se
> Subject: Re: cbm 4032 14 inches enlightment
>
> On 8/22/06, Gabriele Bozzi <mabuse68@gmail.com> wrote:
>> Hallo list,
>>
>> Last week I gathered in one of my "raids" a CBM 4032 sporting a 14
>> inches monitor (ya, baby has a big head).
>> When the guy switched it on it chirped like an 8032 and, to my little
>> astonishment, I found this evening that ,indeed, the motherboard is
>> marked as 'ASSY 80320080' and somewhere is clearly written '80col'.
>
> Yep. What you have there is a "Fat Forty".
>
>> Sooo... I understand the video circuitry of the series 80xx is miles
>> away from the one driving classic PETs monitor...
>
> I wouldn't say miles away - the resolution is different, so you can't
> drive a 40-col monitor with an 80-col board, but electrically, the interface
> is about the same (Hsync, Vsync, and Video Data). It's just a question
> of timing.
>
>> what I do not
>> understand is why Commodore had to provide an 8032 motherboard for a
>> 40 column product if just monitor size was concerned.
>>
>> Even the keyboard is not a 'business' keyboard: all graphics symbols
>> have been preserved... Why doing this if a 40xx specimen already
>> existed?
>>
>> Maybe was this machine upgradeable to 80 columns? Or just a freaky
>> 40xx serie's brother?
>> I cannot figure out for what was the extra effort being worth !!!
>>
>> Please, somebody enlight me ;-)
>
> It's all about manufacturing cost. There are, essentially, three generations
> of PET motherboards - the old static PETs, 40-column "Dynamic" PETs
> (using DRAM, not SRAM), and "Universal" PETs. The first two types
> have a video circuit that's discrete TTL and 40-columns only. By the
> time the 8032 came around, there was demand for 80-column machines for
> business apps, but there was still demand for 40-column machines for
> older apps and for home users. It didn't make good business sense to
> continue to make two different enclosures, support two kinds of video
> hardware, two motherboard types, etc. What the engineers at Commodore
> did was to design one board with a 6545 CRTC (nearly identical to the
> 6845 that appeared later in IBM PC Mono boards), and have jumpers and
> ROM differences determine the video timing and resolution.
>
> It's entirely possible to swap ROM sets and fiddle the solder jumpers
> on a "Universal Dynamic PET" motherboard to turn it into either a 4032
> or 8032 motherboard. Because there were still plenty of non-business
> types who wanted the graphic keyboard, that was maintained as an
> option for a long time, but I think in the end, the last PETs produced
> were probably 80-column, business keyboard 8032s.
I have a PET with a universal mother board in which I have replaced the
jumpers with DIP switches. I also have a ROM switch on the screen editor
ROM, which handles the keyboard and screen. I flip the DIP switches and
the ROM switch to change from 8032 t0 4032. I do have to change the
keyboard manually, and manually remove one of the logic chips controlling
the screen memory.
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