4004 and IC history / was Re: Vintage computer photogallery

---snip---> > - RAM: no provision it appears, so you still need a 4002 > (or get by with registers, or via I/O) Hi It looks like one would need to build a full bus monitor. One would no longer need the 4008/9 since one could use the same circuit to moitor all. The way the ROM and RAM chips work is that they watch the instructions on the bus, going to the processor. When they see instructions that require specific actions, they then execute that operation on the bus. As an example, if they see a write to RAM, the RAM chip sees the instruction and then does the write at the correct timing cycle. One can use the circuitry used for the EPROM on the SIM4-01 as an example of how to monitor the instruction flow. With some extra work, one doesn't need 4002s. They do show up on ebay now and then. Do remember, there are two types. There are 4002-1s and 4002-2s The enable is inverted so these can be used on the same select line. Dwight _________________________________________________________________ Windows Live Hotmail and Microsoft Office Outlook ? together at last. ?Get it now. http://office.microsoft.com/en-us/outlook/HA102225181033.aspx?pid=CL1006269…