H5 ROM programming/compatibility

Information and progress towards the H5 board.
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thomasM74
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Joined: Sat Feb 26, 2022 2:51 pm
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H5 ROM programming/compatibility

Post by thomasM74 »

Hello all

Got a question, regarding the ROM for Phoenix H5 (C1 for me, but valid probably for all MB revision) ...

I do have now the 1.04/2.06 chip, 27C4096 with capacity of 512KB, also some spare empty chips.
Since I do not have the decoder, obviously the upper half (2.06 ROM code) is not usable, my H5 boots into TOS 1.04.

My question is: if I program another 27C4096 chip with the two ROMs reversed, 2.06 first, would it work, the H5 booting in TOS 2.06 ?
I mean, logically the answer would be yes but because the 1.04 is 192k and the 2.06 is 256K I decided to better ask first.

Especially since 27C4096 are One-Time-Programable chips :)

Or maybe put it even more generic: if I program any kind of valid (compatible, bootable) 256K ROM in the first half of EPROM chip, would that work (on a H5 motherboard without decoder) ?

Thx.
Thomas
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JezC
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Joined: Mon Aug 28, 2017 11:44 pm

Re: H5 ROM programming/compatibility

Post by JezC »

Hi, short answer is no.

You need additional decoding to get the 256k ROM to work on the basic board.

There are decoders in the shop and on the ST-TF536 plus others (on TRUDIE for example).

Another option might be to run a RAM image of the OS - that avoids the decoding issue.
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thomasM74
Posts: 6
Joined: Sat Feb 26, 2022 2:51 pm
Location: EU

Re: H5 ROM programming/compatibility

Post by thomasM74 »

Understood.

Thx. for information.
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