From: Ethan Dicks (ethan.dicks_at_gmail.com)
Date: 2006-08-21 23:57:44
On 8/22/06, Gabriele Bozzi <email@example.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. -ethan Message was sent through the cbm-hackers mailing list
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