exxos's Atari, Amiga & retro forum

Dear All.

I have been looking into how FastROM can be activated, mainly on the Mega ST motherboard. Some of the research I have done says the ST has 0 wait states (for ROM), yet some info says that there is a ROM delay. My HBS240 accelerator board has jumpers for 0,1,2 wait states, when set to 0, and the CPU running at 16Mhz, the FastROM result is as expected. However, some of my accelerators don't have FastROM jumpers, so I was wondering if anybody can explain to me how this could be achieved?



I have 45ns and 70ns ROM chips in place. They made a fractional difference, but not the desired difference, i.e Gembench 6 reports around 170% (no CPU cache)when successful, as does the Exxos 16Mhz booster with FastROM enabled.

I have read some Exxos info about when he/they were developing the 32Mhz CPU/FastROM booster for the STE. It talked about changing a resistor and/or reprogramming a GAL chip to control ROM speed/delay.



Can anyone please give me some 'easy to understand' technical info? I could be out of my depth here, but eager to learn still. Many thanks.



Regards James

I'm not really sure what you're asking...

The 16mmhz booster gives these results https://www.exxosforum.co.uk/atari/last ... /index.htm

There are no waitstates involved as the ROM is 55ns and can easily keep up with 16mhz.

32mhz also works on the same ROM.

https://www.exxosforum.co.uk/atari/last/V1STE/index.htm

There's nothing else to it.

As for other boosters and boosters and the what they do, no idea.

Hello Exxos. Thank you for your reply.

I will explain it a different way. I have some boosters/accelerators with FastROM and some without. So I will use my HBS240 as the first example. It has jumper settings to enable FastROM/FastTOS. If these jumper settings are set to off, the ROM/TOS speed reports 100% in Gembench 6. When set to 0 wait state, Gembench 6 reports around 170%. However, I can't do this with my T16 or 3rd Coast 16Mhz boosters (yes they can use CPU cache, but this isn't the same as FastROM). Is there a way to speed up ROM/TOS speed for these 16MHz boosters please? Can a mod be made on the STFM/Mega motherboard or would the mod need to be on the CPU accelerator board please? Hope this makes sense. If not pls let me know, and I will try to explain it differently again. Many thanks.

Regards James

Speeding up someone else's boosters without explicit circuit diagrams and GAL code would be next to impossible I think. Even if you had those it would be a phenomenal amount of work to figure it all out and make corrections. I don't believe anyone would invest the amount of time into such a project.

exxos wrote: 09 Jun 2025 14:53 Speeding up someone else's boosters without explicit circuit diagrams and GAL code would be next to impossible I think. Even if you had those it would be a phenomenal amount of work to figure it all out and make corrections. I don't believe anyone would invest the amount of time into such a project.

Ok thank you for your advice. The more I think about it, the more I think whoever designed the boosters put delays in on purpose so the booster would work with the slower ROM chips such as 200ns and 250ns. If I use my HBS 240 at full ROM speed with old slow ROM chips, the machine won't boot at all. If I fit my 45ns or 70ns ROM chips, there is no problem. The Third Coast booster has socketed GAL chips, so might take a look at what is on them. Many thanks again.

Regards James