640-KB
Micro 8088 default turbo option
I've noticed that the default CPU clock set for Micro 8088 is 9.54 MHz, 4 RAM WS and this is not good, as it will fail on boards with 14.3MHz quartz. 7.15 MHz, 0 RAM WS would be much safer.
Is there any option to switch the "Turbo Mode" ON and OFF?
Yes, the speed is hot-key switchable during run time with the ctrl-alt-+ key stroke, which toggles between the default speed of 9.54MHz, 4 RAM WS and 7.15 MHz, 0 RAM WS.
This behavior is in fact customizable by changing TURBO_TYPE = TURBO_REV to TURBO_TYPE = TURBO_STD in the Configuration for micro_8088, which will make the startup speed be the "non-Turbo" 7.15 MHz, 0 RAM WS and the ctrl-alt-+ speed be the 9.54MHz, 4 RAM WS.
Alternately the FE_CPU_CFG value can be customized too for the default speed if it was ever desired to be something other than the current default of 011b for 7.15 MHz, 0 RAM WS or 100b for 9.54MHz, 4 RAM WS.
Your suggestion makes a lot of sense though to have an option so that boards with the slower quartz will work properly, which could look like either a separate image - perhaps the high-speed boot in the "high" image and the low-speed boot in the "low" image or possibly a configurable byte in the Flash image. Would that do the trick?
Thanks for the testing and the suggestion! Let me work on this a bit and I'll post an updated image.
Actually, for me, after changing crystal to 28.64MHz it switches between 9.54MHz and 4.77MHz, but that's completely fine. I may or may not have sth to do with the fact I'm using a Proton PT8010AF chipset, as the Faraday FE4010A is impossible to buy.
That's interesting. Perhaps the PT8010AF has slightly different speed register settings. How does it work on the micro_8088 BIOS?
On Micro8088 BIOS I have all 3 speeds (4.77MHz, 7.15MHz & 9.54MHz) available. I have verified clock frequency, with a frequency counter.
I just looked back at the code and toggling between highest and lowest (4.77) was what I intended (I just forgot that's how it worked). I'll look into what it would take to add three state toggling for it.