Author Topic: ROM Board with SRAM.  (Read 883 times)

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Offline rpalmer

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ROM Board with SRAM.
« on: 14:43, 12 May 21 »
Well folks after a period of time I have managed to create a ROM/RAM board which can now handle 32K EPROMs.
There is a 3rd ROM socket for the OS/BASIC ROM which can be used to hold and external OS as required. This is now likely to soon be enabled.

I will also be able to use an SRAM chip to hold upto 63 ROM Images.The SRAM chip is battery backed using a CR2032, meaning it can act just like a flash memory version.
The intent of the board is to have enabled FHOSIL (AKA HDOS32) which will enable my system to access the IDE interface (also under development) and CF card which will hold eventually my software and stuff for my development of EVA (External Video Adapter) - You can find this elsewhere on the forum.
Here is a Youtube link to a 28 second video of it in operation:
https://www.youtube.com/watch?v=omXrzrynSoU(Sorry for the poor lighting and image quality but I have poor lighting for where I have my CPC positioned and my attempt to improve the situation was well not good enough, but you can get an idea of is going on).
rpalmer

Offline GUNHED

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Re: ROM Board with SRAM.
« Reply #1 on: 17:26, 12 May 21 »
63 ROMs is just nice!!!  :) :) :)
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Offline ComSoft6128

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Re: ROM Board with SRAM.
« Reply #2 on: 17:32, 12 May 21 »
EVA?

Offline SkulleateR

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Offline zhulien

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Re: ROM Board with SRAM.
« Reply #4 on: 08:22, 18 May 21 »
why 63 roms and not 64?

Offline Bryce

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Re: ROM Board with SRAM.
« Reply #5 on: 09:55, 18 May 21 »
Probably because he has one space reserved for the LowerROM?

Bryce.

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Re: ROM Board with SRAM.
« Reply #6 on: 19:54, 18 May 21 »
why 63 roms and not 64?
The checksum of 63 is 9 and 9 is the prefect number.  8)
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Offline zhulien

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Re: ROM Board with SRAM.
« Reply #7 on: 20:53, 19 May 21 »
Probably because he has one space reserved for the LowerROM?

Bryce.


I would hope the lower rom is available as normal so hack it can be put there.

Offline rpalmer

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Re: ROM Board with SRAM.
« Reply #8 on: 23:17, 19 May 21 »
zhulien,
Yes there will be a Full ROM 0 which has both the lower and Upper ROM slot.
The reason there is only 63 ROMs is that ROM 0 cannot setup in RAM, whereas all of the other ROM positions can.
rpalmer

Offline GUNHED

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Re: ROM Board with SRAM.
« Reply #9 on: 18:55, 20 May 21 »
Not sure if I understand you right, however there are ROM 0 replacements (which don't make much sense, but they work).
http://futureos.de --> Get the revolutionary FutureOS (Update: 2021.01.24)
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Offline TotO

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Re: ROM Board with SRAM.
« Reply #10 on: 20:07, 20 May 21 »
I can imagine that is because the CPC ROM is 32K and only the upper 16K are mapped as ROM0 for the BASIC and the lower 16K are as mapped to #0000 for the firmware (no ROM ID to access it).
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Offline GUNHED

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Re: ROM Board with SRAM.
« Reply #11 on: 02:41, 21 May 21 »
Well, the good Dobberting EPROM expansion can also use 32 KB EPROMs, but you can (using jumpers) set a ROM number (0-15) for every single 16 KB block of ROM.
http://futureos.de --> Get the revolutionary FutureOS (Update: 2021.01.24)
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Offline Bryce

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Re: ROM Board with SRAM.
« Reply #12 on: 10:06, 21 May 21 »
Not sure if I understand you right, however there are ROM 0 replacements (which don't make much sense, but they work).

Why don't they make much sense? The LowerROM board is one of the boards I use most often.

Bryce.

Offline GUNHED

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Re: ROM Board with SRAM.
« Reply #13 on: 16:45, 21 May 21 »
Why don't they make much sense? The LowerROM board is one of the boards I use most often.

Bryce.
Obviously I talked about ROM 0 (the BASIC ROM) and not the lower ROM (Firmware).
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Offline zhulien

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Re: ROM Board with SRAM.
« Reply #14 on: 03:49, 27 May 21 »
If you haven't used Siren's HackIt ROM, it is a replacement ROM 0 that you can switch in and reset the CPC in the middle of a game - it takes over in some ways like a multiface 2, but you cannot resume the game again - you can however manipulate memory, save it and various other things which make it a really handy debugging / cracking tool.


My ROMBO RomBox works 100% with a HackIt ROM in slot 0 - of course that is a physical ROM and there is no reason for CPC modern ROMBoards to allow selection of that ROM via an alternative mechanism for programming, but then via a button for selection with the reset.

Offline GUNHED

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Re: ROM Board with SRAM.
« Reply #15 on: 18:04, 27 May 21 »
Multiface II does switch in an 8 KB lower ROM (and 8 KB SRAM). Don't know about Hackit though.
http://futureos.de --> Get the revolutionary FutureOS (Update: 2021.01.24)
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