Search found 3 matches

by graz
Mon May 07, 2018 5:22 pm
Forum: ROM UPGRADES
Topic: Strange TOS 1.04 Issue
Replies: 6
Views: 1667

Re: Strange TOS 1.04 Issue

Thanks to everyone for the suggestions. As I said, those EPROMs were in the machine when I got it and worked with the older TOS. I have to assume they're rated fast enough, but I can't actually find any information about NEC D27256D and don't know what speed they are actually rated for. I have anoth...
by graz
Mon May 07, 2018 4:31 pm
Forum: ROM UPGRADES
Topic: Strange TOS 1.04 Issue
Replies: 6
Views: 1667

Re: Strange TOS 1.04 Issue

Attached. TOS104US.{LO0/LO1/LO2/HI0/HI1/HI2}. Original 192K image from tos104us.zip from the above site. Those ones were split with ROMSPLIT on Steem and verified as identical to the burned ROMs.
by graz
Mon May 07, 2018 4:08 pm
Forum: ROM UPGRADES
Topic: Strange TOS 1.04 Issue
Replies: 6
Views: 1667

Strange TOS 1.04 Issue

I have been trying to upgrade my 520ST from TOS 1.02 to 1.04. It had six NEC D27256D EPROMs in it containing the old TOS and were working fine. I erased said EPROMs in a real EPROM eraser (none of this leaving them in the sun business) and then programmed them with a QG-4X programmer which I've used...

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