On Wed, Dec 25, 2019 at 06:55:59PM +0000, jim bell wrote: > On Wednesday, December 25, 2019, 09:44:21 AM PST, jim bell > <[email protected]> wrote: > > > >The New York Times: Chuck Peddle Dies at 82; His $25 Chip Helped Start the > PC Age. > https://www.nytimes.com/2019/12/24/technology/chuck-peddle-dead.html > >6502 microprocessor. > I was a fan of the Z80 microprocessor, which I viewed as 'the 8080 done > right'. https://en.wikipedia.org/wiki/Zilog_Z80 > Single +5 supply, single-phase clock, TTL compatible I/O (except > for the CLK, which was pulled to +5 with a resistor), and a decoded > memory and I/O system.
What does that mean (decoded memory, decoded IO)? > I also thought the relatively large number > of internal registers, much more than 6800 or 6502, was more > efficient, minimizing memory accesses. The Z80 also had a > mirrored set of registers, and an enhanced instruction set, > including relative-addressing. It also generated a 7-bit refresh > address, making use of DRAM easy. This, however led to a problem > when some DRAM manufacturers of 64K DRAMs (I think, including > Micron Technology) built DRAM chips needing an 8-bit refresh > address. It meant that those DRAMs simply would not work > (reliably) if they depended on Z-80 refreshing. If Zilog had only > added another counter to that chip in the beginning! > Starting in the summer of 1978, I built my homebrew "Bellyache I", the name > parodied from the "Illiac IV". https://en.wikipedia.org/wiki/ILLIAC_IV > I used what would look like S-100 bus hardware, but I was so disgusted by > the (lack of) 'architecture' in the S-100 that I merely used a motherboard > and prototype boards, and I completely re-defined the bus. This meant that I > only could add functions I myself had designed and constructed. The > Bellyache I eventually had as many as 600 IC's, and this included my > prototype "SemiDisk", a S-100 prototype card with 32 memory sockets, each > with 8, 2118 (16K, 5-volt only) DRAMs in CERDIP packages, stacked 8 chips > high. This was completed in about October 1980. (I started work at Intel > early July 1980) It looked like a brick, and weighed just about as half of > one! In implementing that, I had just invented the Disk Emulator, or > semiconductor disk. Technically, there may have been a similar thing for > mainframes, but mine was the first for Personal Computers. > My company, SemiDisk Systems, Inc, eventually built boards for the S-100 bus, > Radio Shack Model 2, IBM PC (8-bit bus), IBM AT (16-bit bus), and the Epson > QX-10. > Jim Bell
