3 ms·
I think they used SRAM and not DRAM, which is how it was faster than a clock cycle.
by smolder 3y ago
I think they used SRAM and not DRAM, which is how it was faster than a clock cycle.
- Gracana 3y agoNope, they used 16k x 1-bit DRAM ICs.
- monocasa 3y agoBoth were faster. DRAM was a little cheaper, but required more circuitry to handle refresh on most CPUs making it a wash cost-wise on some designs. Typical woz engineering got the cost of the refresh circuitry down to where DRAM made sense economically on the Apple ][. Interestingly Z80s had DRAM refresh circuitry builtin which which was one reason for their prevalence.
- peterfirefly 3y agoScreen output was the DRAM refresh. And for the Z80: also that it only needed GND and 5V. The 8080 also needed 12V. And the Z80 only needed a single clock phase -- the 8080 needed two. The 6502 also only needed 5V and a single clock input (the 6800 needed two clock phases). The 6502 and Z80 were simply a lot easier to work with than most of the competition.