I discovered that the m27c160 has a slightly faster access time than the m27c801 so it allows me to overclock games faster. I managed to get starfox 1 running fine on the chip by doubling the rom image in a hex editor and burning it. The highest address line I just tied to ground. I tried the same trick with stunt race fx and starfox 2 and they glitch out a bit then freeze. Did I do something wrong?
It doesn't have a faster access time. Access time is on the specific part. There are various speeds for both Chip models.
If you don't need the full capacity of a chip you should double your ROM image till it fits, and then tie the unused address lines to ground which you did get right. But you should remember that if you tie the address line down, you can't have that pin connected to the normal point if it sits on a bus because you'll be shorting that address line for the whole bus.
I don't know why it worked for you once but not the other times. Check your connections I guess.
Yes I didn't connect the pin to anything but ground. And yes I doubled the images of all games I burned. Tomorrow I'll try running stunt race fx and starfox 2 at default clock speeds and see if that helps at all. Stunt race fx has weird things happening I'll be driving normally and suddenly my car will jump and take damage like I just drove into an invisible wall.
Also any theories as to why the 27c160 runs faster if it's not access speed?
*edit* darn it does seem to be an overclock related thing. Any idea why starfox 1 overclocks super fast with this chip but other games don't?
I don't know, you never mentioned any access timings for either chip you are using. When you're trying to overclock you need the ROM to keep up. Normal MaskROMs are probably slower than the more modern memory you can get these days. Glitches and crashes are expected when you alter the timing of the hardware anyway.
Well the sad thing is this 27c160 barely increases the speed, oh well. More luck than anything else haha. As for access speed I burned some rom images to a m27c801-80 (80ns) chip and it made no difference. It just seems these ST chips overclock better than the Amtel chips.