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The Gigatron project
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H.G.Muller



Joined: 10 Mar 2006
Posts: 21542
Location: Amsterdam

PostPost subject: Re: The Gigatron project    Posted: Tue Dec 05, 2017 8:58 pm Reply to topic Reply with quote

Indeed, that is also what shocked me. I was building TTL projects of similar complexity at that time. Below, for instance, is a photograph of a video card I designed, for displaying a 512x256 monochrome pixel matrix on a televison or composite-video monitor. It was also put together entirely from small-scale-integration TTL chips, (counters, multiplexers, adders, and a 32x8 TTL PROM), plus a few (16Kx1) DRAM chips.



But it never occured to me that you could also build an entire CPU this way. I was using such stuff to expand the capabilities of my 6809-based computer. The TTL was potentially much faster than any microprocessor you could buy those days. The clock rate of the video card above was 10.24MHz, my CPU was only running at 1MHz. (Although really only the pixel shift register and a counter acting as sequencer for the PROM delivering the DRAM control signals was running that fast; the rest was running at 1.25MHz, the DRAM cycle rate. But for TTL this was still slow.)

If I had realized this, I probably would have built my own CPU for running a Chess program, in those days. I must admit, however, that the Gigatron seems to use better memory chips then were available in the early eighties: a 32K x 8 static CMOS RAM with 70ns cycle/access time, and a 64K x 16 EPROM with 100ns cycle time, the whole thing running with a 160ns cycle. The static RAMs I was using in my 6809 computer where 1K x 4 2114 chips, with an access time of 200ns. So I might have had difficulty to go beyond 5MHz, although this stuff could usually be heavily overclocked, if you kept it at room temperature, and did not load the outputs to maximum specs. Nevertheless it intrigues me to think what I could have built to make the maximum of that. Probably something with a Harvard architecture, and a quite wide instruction bus (like 24 bits), so that each word from program memory could encode for one memory operation and two instructions, the CPU running twice as fast as the memory. I would not have had as much memory as the Gigatron, however.


Last edited by H.G.Muller on Tue Dec 05, 2017 9:07 pm; edited 1 time in total
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Subject Author Date/Time
The Gigatron project H.G.Muller Tue Dec 05, 2017 6:32 pm
      Re: The Gigatron project H.G.Muller Tue Dec 05, 2017 7:12 pm
            Re: The Gigatron project H.G.Muller Tue Dec 05, 2017 9:45 pm
                  Re: The Gigatron project H.G.Muller Wed Dec 06, 2017 2:44 pm
                        Re: The Gigatron project H.G.Muller Wed Dec 06, 2017 11:05 pm
                              Re: The Gigatron project Rémi Coulom Wed Dec 06, 2017 11:51 pm
                              Re: The Gigatron project H.G.Muller Sun Dec 10, 2017 11:51 am
                                    Re: The Gigatron project H.G.Muller Sun Dec 10, 2017 10:10 pm
                                          Re: The Gigatron project Rasmus Althoff Sun Dec 10, 2017 10:20 pm
                                                Re: The Gigatron project H.G.Muller Sun Dec 10, 2017 10:30 pm
                                          Re: The Gigatron project Stefano Gemma Mon Dec 11, 2017 11:15 am
                                                Re: The Gigatron project H.G.Muller Mon Dec 11, 2017 12:15 pm
                        Re: The Gigatron project Rasmus Althoff Thu Dec 07, 2017 9:44 pm
      Re: The Gigatron project Stan Arts Tue Dec 05, 2017 7:23 pm
      Re: The Gigatron project Dann Corbit Tue Dec 05, 2017 8:11 pm
            Re: The Gigatron project H.G.Muller Tue Dec 05, 2017 8:58 pm
      Re: The Gigatron project Rasmus Althoff Tue Dec 05, 2017 9:04 pm
      Re: The Gigatron project Fulvio Benini Wed Dec 06, 2017 8:31 am
      Re: The Gigatron project Martin Sedlak Wed Dec 06, 2017 11:42 am
            Re: The Gigatron project H.G.Muller Wed Dec 06, 2017 12:15 pm
                  Re: The Gigatron project Martin Sedlak Thu Dec 07, 2017 10:48 pm
      Re: The Gigatron project Ian Osgood Thu Dec 07, 2017 12:17 am
      Re: The Gigatron project Rémi Coulom Thu Dec 07, 2017 9:58 pm
            Re: The Gigatron project H.G.Muller Fri Dec 08, 2017 8:45 am
                  Re: The Gigatron project Stefano Gemma Fri Dec 08, 2017 11:07 pm
                        Re: The Gigatron project H.G.Muller Sat Dec 09, 2017 1:16 pm
                              Re: The Gigatron project Stefano Gemma Sat Dec 09, 2017 1:44 pm
                                    Re: The Gigatron project H.G.Muller Sat Dec 09, 2017 2:21 pm
                  Re: The Gigatron project Rasmus Althoff Sat Dec 09, 2017 7:27 pm
                        Re: The Gigatron project H.G.Muller Sat Dec 09, 2017 8:29 pm
                        Re: The Gigatron project Charles Roberson Sat Dec 09, 2017 9:30 pm
                              Re: The Gigatron project Rasmus Althoff Sat Dec 09, 2017 9:36 pm
                                    Re: The Gigatron project Martin Sedlak Sat Dec 09, 2017 9:57 pm
                                          Re: The Gigatron project Rasmus Althoff Sat Dec 09, 2017 10:10 pm
                                                Re: The Gigatron project H.G.Muller Sat Dec 09, 2017 11:31 pm
                                                      Re: The Gigatron project Stefano Gemma Sun Dec 10, 2017 9:01 am
                                                            Re: The Gigatron project H.G.Muller Sun Dec 10, 2017 11:32 am
                                                                  Re: The Gigatron project Stefano Gemma Sun Dec 10, 2017 12:24 pm
                                                                        Re: The Gigatron project H.G.Muller Sun Dec 10, 2017 8:44 pm
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