From: J Ellsworth (c1_at_syndicomm.com)
Date: 2007-03-28 00:16:22
More from bil, "Well there ya go.. Clearly a TED, the unnamed 40pin chip is something like a 7501 cpu which is a processor with a gated r/w line to hold the line valid through the DRAM cycle. I added U1 myself as the design when I got to CBM tried to use the 7406 as a level detecting reset circuit. The design also called for the data lines to go directly out the keyboard port (hence diodes, Germanium no less, to keep the data lines from shorting out when you pressed multiple keys) which was also the joystick port. the problem was the noise the joystick port would pick up would create sparkles in the picture due to blown data. I added an 8 bit latch (nmos MOS 8529 or something like that) to isolate the data lines form the keyboard/joystick. When my boss walked in after he had given me a "just fix it attitude" when I was explaining the original TED design (remember I inherited TED), I was playing a video game. When he gave me a hard time about why I wasn't working on the problem I pointed the monitor, which he totally failed to grasp the significance of. Finally he realized I had taken the case off the monitor and wrapped 6 foot of joystick cable around the yoke of the picture tube and there were still no sparkles. Since he had been short with me, I was short with him, the only thing I would say was "it's fixed", since he obviously didn't want to know what was wrong I assumed that he didn't want to know what fixed it. I made that guy a lot of money over the next 2 years." Jeri -----Original Message----- From: firstname.lastname@example.org [mailto:email@example.com] On Behalf Of Ethan Dicks Sent: Tuesday, March 27, 2007 4:31 AM To: firstname.lastname@example.org Subject: Re: TED based motherboard On 3/27/07, Anders Carlsson <email@example.com> wrote: > Hello, > > I have come across an unknown, TED based motherboard which I would appreciate pointers about. It only has 14 chips, named as following: > > U1 = NE555N 8144 8-pin timer chip (date code 44th week of 1981) > U2 = P8214A DM7406N 7406 open collector inverter (early 1982) > U3 = U4LS139N 8137 SA dual 1-of-4 decoder (mid 1981) > U5 = INMOS 8329-A IMS 2629P-15 C1059A KOREA > U6 = INMOS 8329-A IMS 2629P-15 C1065A KOREA Given the "-15" and that there are two of them, I'd say these are DRAM, perhaps 16Kx4 each. > U7 = 74LS257AN 8216 SA > U13 = 74LS257AN 8216 SA tri-state quad 1-of-2 selectors > I tried to power it up, despite lacking some chips. It makes a faint buzzing noise. Using a video cable, the monitor detects power on, but no picture. Using RF, there is no signal at all, at least not at UHF 36. I noticed the RF modulator has a small switch, which suggests it may be a NTSC unit rather than PAL? US RF modulators typically have a switch between stations 3 and 4 (We have a broadcast channel 4 in my area, and others have a channel 3). > I see that Zimmers have some schematics for different Plus/4, Commodore 16 and 116. Which one would best match this board, and how can I find out which chips should go into U4 (logic gate?) and U8 ? Probably it'd be tricky to get working anyway, given that fully equipped Plus/4 tend to break in CPU and TED chips, much less a loose board that for some reason has been sitting on a shelf for 15-20 years. I would start with the EPROMs and the TED, since those are known chips. U4 is probably some flavor of 82S100, but that won't help define any signals by itself. You can probably verify the data and address busses and check the DRAMs. Without knowing what memory map the board is supposed to have, fabricating a new 82S100 map is going to be a bit tricky. Interesting specimen. It seems to have been made early in the C-64 days. -ethan Message was sent through the cbm-hackers mailing list Message was sent through the cbm-hackers mailing list
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