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. 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
