PC-9801FA motherboard jumper and CPU accelerator

Started by yukin, September 02, 2014, 11:58:58 PM

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I have a PC-9801FA for a long time now. I have a CPU accelerator installed since i got the computer. It's a Buffalo HFA-16H who is multiplying the cpu speed up to 6x time. So i have 96mhz.

When i try Touhou by example, i can see that my computer doesn't run that fast. It is slow the majority of the time and if i remove the cpu accelerator, it doesn't change anything.

I think maybe there is a jumper and/or dip sw on the motherboard first that need to be setup correctly and also there is a dip sw on the CPU accelerator but i cannot find anything about it.



The PC-9801Fa series is basically (along with most upgrade CPUs) described here:


If the info from the above site is unable to help you, I have three possible ideas to why it is not working:

1. You need some sort of program to get it to work (something to do with cache). The Viper Powermulti thread here has several useful links on it that you could use.

2. The hardware is unable to support the upgrade. Perhaps it is a lack of RAM or the overall max speed the hardware can support is low. I'm pretty sure the Fa series was originally intended to be upgraded with i487, so the hardware might have issues with a newer CPU. That link I posted probably provides more info into this, however.

3. For some reason, the new CPU is not disabling the i486. This can be caused by numerous reasons, including a wrong pin layout or incompatible hardware.

By the way, exactly how slow do the Touhou games run on the PC-9801 Fa's original i486 (16 Mhz)? Are they even playable?


Yeah, i already checked on the website. I think they say something about a jumper setting but there is not additional info.

I can play touhou but slow as hell sometime. If there is 0 enemy on the screen, the game play great. if there is some enemy with bullets, it is a little slow. boss fights are very slow but playable(make it too easy to dodge bullets)

I will get myself a new 486 ODP and will try. But i think i really do need the jumper configured correctly and i don't know the settings.