Beta-07 has improved support for the IBM Personal Computer Power Series 850 Model 6070 (RS/6000 7248 (43P)).

lolo799 wrote on 2025-08-13, 18:08:

I'll test the new version when I can, in a week or 10 days from now.

I have just released SIV V5.83 Beta-08 which further improves the Windows NT V4.00 SP2 + PowerPC support so please use that.

Sorry, it took a while.
The iBook hdd is having problems coldstarting.

lolo799 wrote on 2025-09-06, 16:44:

The iBook hdd is having problems coldstarting.

Thank you and I guess this is down to the age of the system. I had to replace the disk in my Motorola PowerStack as there were a vast number of bad blocks, I hope the replacement keeps working.

Since your last run I changed SIV to read the TB (mftbu+mftb) but the returned values are not what I expected which is why the speed is reported as 133 MHz, what speeds are reported when the system posts?

For PowerPC 604 I need to scale the value by 8 and wonder if I need to scale it by 30 for PowerPC 750cx, but feel I need to see what happens with a few other CPUs to figure out what is needed. Looking at http://www.cap-lore.com/code/TB/ it specifies scaling by 16.

red-ray wrote on 2025-09-06, 17:59:

Since your last run I changed SIV to read the TB (mftbu+mftb) but the returned values are not what I expected which is why the speed is reported as 133 MHz, what speeds are reported when the system posts?

The G3 cpu in my iBook is a 500MHz model, with a bus speed of 66MHz.
There's no such thing as a Post screen with system info on a new world mac (there is the Open Firmware shell but it doesn't show up by default) and the NT loader screen only shows the ram available.

You can see what the NT4 setup process looks like using Wack0's fork of the dingusppc emulator, here for example:
https://virtuallyfun.com/2024/07/22/a-quick-v … macintosh-0-05/

lolo799 wrote on 2025-09-07, 09:10:

The G3 cpu in my iBook is a 500MHz model, with a bus speed of 66MHz.

I have been looking into what is happening and it seems that the TB register is not derived from the CPU speed, but rather the FSB speed.

After discovering this I have been pondering how to get the FSB to CPU speed ratio, on recent x32/x64 systems (PentiumPro and later) it's quite easy as it's in a MSR, but for PowerPC this is not the case.

I have just uploaded SIV32P V5.83 Beta-09 which should work, please will you try it and post new save files?

Below is what I got in testing, you should get similar, but with a x7.5 rather than a x2 multiplier. The code should also work when the FSB is 100 MHz, etc., but I don't have a system I can test this on.

Here you go:

lolo799 wrote on 2025-09-08, 17:58:

Here you go:

Thank you, the ratio calculation worked as I hoped it would. I have just uploaded SIV32P V5.83 Beta-09 which includes a few more improvements, it really needs to be validated with a few more CPU types/speeds though.

Above is using the Tahoma font, below is what happens when it's not installed.