Re: Modifying microcode
On 06/02/2018 03:33 PM, Antonio Carlini via cctech wrote: On 02/06/18 15:17, allison via cctech wrote: It was my understanding from using the 730 that there was limited (really limited) microcode enough to load the WCS as the tu58 was a serial device (standard tu58) and the 730 had to unpack and stuff the WCS. You need little to do that but far from even PDP11 instruction set. The Microcode was loaded was the "what made it a VAX stuff". Allison Well something has to load the ucode but whether that's a fixed part of ucode itself or whether it's a hardware state machine (or something) that feeds the loaded ucode into the appropriate RAM, I don't know. I've never delved that deeply into the relevant FMP sets. Actually, the 8085 could load a small bootloader from 8085 ROM to the 730 microcode. That would be the most logical way to do it, assuming the microcode bootloader was really small. The IBM 360/25 had all microcode in the top 16K of main core memory, and the emulator of your choice could be loaded from binary punch cards. The microcode bootloader was hand-loaded through the front panel switches, and occupied 16 16-bit words. Jon
Re: Modifying microcode
On 02/06/18 15:17, allison via cctech wrote: It was my understanding from using the 730 that there was limited (really limited) microcode enough to load the WCS as the tu58 was a serial device (standard tu58) and the 730 had to unpack and stuff the WCS. You need little to do that but far from even PDP11 instruction set. The Microcode was loaded was the "what made it a VAX stuff". Allison Well something has to load the ucode but whether that's a fixed part of ucode itself or whether it's a hardware state machine (or something) that feeds the loaded ucode into the appropriate RAM, I don't know. I've never delved that deeply into the relevant FMP sets. Antonio -- Antonio Carlini arcarl...@iee.org
Re: Modifying microcode
On 06/01/2018 02:46 PM, Antonio Carlini via cctech wrote: > On 01/06/18 18:40, Eric Smith via cctalk wrote: >> On Fri, Jun 1, 2018 at 11:08 AM, Robert Armstrong wrote: >> Eric Smith wrote: The control stores of the 11/785, 8600, and 8650 were entirely WCS. All other VAXen had (relatively) large ROM control store and tiny WCS or patch store. >>> You forgot the 11/730 and 725. The KA730 used 2901 bit slicers >>> and the >>> control store was entirely in RAM. After power on it was a paperweight >>> until the 8085 CFE loaded the microcode. >> >> Thanks for the correction! I've never used those models. >> > > In the Digital Technical Journal #2 (the one that describes the > development of the MicroVAX II) > > they say that they used the VAX-11/730 as a testbed > > the 78032 chip. The VAX-11/730 was chosen because it was "an entirely > 'soft' machine". > > > (The VAX-11/725 is essentially the same hardware but in different > packaging). > > > Antonio > > It was my understanding from using the 730 that there was limited (really limited) microcode enough to load the WCS as the tu58 was a serial device (standard tu58) and the 730 had to unpack and stuff the WCS. You need little to do that but far from even PDP11 instruction set. The Microcode was loaded was the "what made it a VAX stuff". Allison
