Lower ROM Board

[Bryce]

Hi All,
     I'm hoping to get some quality hardware time in over the Christmas break and was going to make myself a (MegaFlash compatible) Lower ROM board, just to mess about with. Is anyone else interested in having one of these? If so, vote above.
The board will be a simple single EPROM board with on/off switch which allows you to install BASIC 1.1 on a 464 or BASIC 1.0 on a 664/6128. Let me know your thoughts with the poll above and I will see what I can do. The standalone device would also work with the MegaFlash, it just wouldn't plug on top like a module. It will not be flashable or anything fancy, just a simple EPROM. Also: 6128 users would need to put ROM 7 on a MegaFlash or other external ROMBoard, as the Lower ROMBoard disables the internal ROM 7.

Bryce.

[steve]

I would not know what to put in it, I did put basic 1.1 in my 464 when it was possible to buy the rom.
Basic 1.0 was socketed and they may have stopped selling the rom separately because they had, or intended to, stop using sockets.

[Bryce]

That's all there is to put in it. But I just thought I'd ask anyway, because several people were discussing this lately.

Bryce.

[steve]

I was thinking that one day I night try to control a reprap with a CPC and have the software in rom, replacing the arduino, and maybe printing one layer at a time as I draw the object on the CPC.
It takes many hours to print an object so the CPC should be fast enough.

[Bryce]

You don't need to replace ROM 0 to do that though. That software could be in any ROM.

Bryce.

[steve]

Yes that's right, but I might have the control routines in lower rom like the firmware, and have the drawing program in the upper rom.
I would replace the basic rom so there would be no need for an external rom card or box.

[beaker]

Hi Bryce,

Would this work with a 6128+ so I could turn on machine the system cartridge being inserted?

[TFM]

@Bryce: Great to see that you're going to create finally the Lower ROM-Box I've been waiting for such a device for decades.


Now I can change the character set of my CPC every day!!! Yay!!! Guess a Flash can be used instad of an EPROM, so burning can be done a bit more quick.



EDIT:
I know you will beat the carp out of me now, but... what's about a Lower-Flash-ROM-Box, that can be programmed using the CPC itself? *duck-und-weg* 

[00WReX]

So this would mean that I can turn that Spanish 464 I have (with English ROM) back to the way it should be  .

And I'm with TFM/FS, if this could possibly be a flash version...even better. 
But please don't go beating up his carp...leave his fish out of it...

If it could be flash, is there any possibility of incorporating the ROM 7 for those of us without any ROM device / megaflash.



Cheers,
Shane

[Cpcmaniaco]

I Vote as a module that plugs onto the MegaFlash.

But really I would like to have the 2 options, probably many work.

Any of them, I want it for my collection.

[steve]

Would it be possible to redesign megaflash to provide 1 lower rom and 31 upper roms?

[TFM]

So this would mean that I can turn that Spanish 464 I have (with English ROM) back to the way it should be  .

And I'm with TFM, if this could possibly be a flash version...even better. 

Yes you can change it. The character set begins in the lower ROM at address &3800 and ends at &3FFF. So you can have Spanish, French, English character sets and for any other language, just make them. But I like to use once a while a charset that just looks different.

I will go to a c64 meeting and use the c64 charcter set and tell them: "Look I got an c64 emulator on my CPC 464 and it's even faster than the original c64" Hehehehe. (Ok, I change some bytes more in the lower ROM to get the appropriate colors ;-)

Having a lower ROM box will never be boring ;-)

[Bryce]

@Beaker: Technically it would work on a CPC Plus, but you would still need a cartridge inserted for the ACID, so it makes less sense on a Plus.

@TFM: You could use a Flash IC instead of an EPROM, but making the device flashable is pretty much impossible, because the CPC wouldn't boot when it's inserted and hasn't yet been flashed. Even a switch to disable it before flashing would cause a crash as soon as you switched to program mode. It would also make an otherwise small cheap expansion very expensive.

@Steve: Yes, but it would mean a complete re-design and the end result would be more or less the same as a MegaFlash plus the new board. So I don't plan on doing this.

Bryce.

[00WReX]

Will this be a DIY kit or will you provide the option to purchase one pre built ?

[TotO]

I would like a standalone board with 1MB flash chip shared for 512K RAM and 512K ROM (lower & upper)

[Bryce]

Well with only 6 people showing any interest, I may not make any at all. But if I do make some, I would build them completely and supply the EPROM/Flash too, that way I'm sure everyone gets a working device.

@TotO: yeah sure! Should it make coffee too?

Bryce.

[TotO]

No coffee for me, but an AMSDOS patched version for booting |CPM disk from B drive too.

In fact, why doing RAM or ROM board but not both ?
It will cost less for the final user and don't have to plug many boards on the back of the computer.
A 1MB flash IC cost the same price than a 512KB version.

[Bryce]

Well the MegaFlash was designed to have 32 ROMs = 512K, not because 1MB was cheaper or whatever, but because more than 32 ROMs at one time on a CPC doesn't make sense. As far as RAM and ROM on one board is concerned, I keep them seperate because some people only want one of the two and aren't prepared to pay double for the half that they don't want/need. There are plans however for a MegaFlash RAM Module add-on, so you have both, but still only have one device plugged on to the back of the CPC, but more about that later...

Bryce.

[TotO]

Well the MegaFlash was designed to have 32 ROMs = 512K, not because 1MB was cheaper or whatever, but because more than 32 ROMs at one time on a CPC doesn't make sense.

I know. I said a 1MB chip may be shared for 512K RAM / 512K ROM.

As far as RAM and ROM on one board is concerned, I keep them seperate because some people only want one of the two and aren't prepared to pay double for the half that they don't want/need.

They don't cost the double because using the same memory chip and only one PCB instead of two or tree. May cost 10% to 20% more.

There are plans however for a MegaFlash RAM Module add-on, so you have both, but still only have one device plugged on to the back of the CPC, but more about that later...

Megaflash + Lower ROM + RAM modules ?

[beaker]

Just thinking about the possibility of making my 6128+ machine as universal as possible: if it fits in the Megaflash and overrides the system cartridge, I could have the French 'Downgrade' System Cartridge on your proposed unit as it's something I wouldn't need very often but could be useful to have at the click of a switch (as opposed to an hacked cartridge that I'd probably misplace and spend half the day looking for).

In regards to another hardware project Bryce, did you ever make a batch of the PS2 mouse interface (http://www.cpcwiki.eu/index.php/PS2Mouse) or was it only a DIY project? I was also thinking if FutureOS can be placed at ROM 0 then the 2 may complement each other

[Bryce]

@totO: You can't split the IC into ROM and RAM: The MegaFlash uses a Flash IC, that can only be read in complete pages and only has a certain amount of write cycles. If it used a 1MB RAM IC, then it would need a battery backup and would be called a MegaBatteryBackedRAMThingy (doesn't sound as cool) The main advantage of the MegaFlash is that it doesn't need a battery. Also, the price wouldn't be doubled because of the price of the Memory IC, rather it would need a much bigger PCB and several more TTL ICs, which is what really drives the price up.

@Beaker: One solution for your universal 6128+ might be another project of mine that I never released. The "ACID Inside" is a small PCB that gets soldered to the back of the riser PCB inside the Plus (The PCB with the Cartridge Socket). Its just a tiny PCB with an ACID on it, but it means that the cartridges don't need to have an ACID, so homemade ACID-less cartridges work and it would also be possible to use the Lower ROM/ MegaFlash solution to swap the Firmware. I only ever built one and never released the schematics, but if anyone is interested I can search them out and put them on the Wiki.
As far as the USB and PS/2 Mouse Adapters are concerned, I think I made about 6 or 7 of them, I probably still have one somewhere if you want one.

Bryce.

[beaker]

Hi Bryce, yes please if you have one of the mice adapters going spare. PM me with the price and I'll transfer the money to you

That ACID inside sounds perfect. I assume the machine wouldn't freak out if there are 2 acid chips present, for example if I inserted a normal game cartridge into the slot? Also would I need previous experience of making my own PCB's, or would it be a good starter project to learn how to?

[TFM]

@TFM: You could use a Flash IC instead of an EPROM, but making the device flashable is pretty much impossible, because the CPC wouldn't boot when it's inserted and hasn't yet been flashed. Even a switch to disable it before flashing would cause a crash as soon as you switched to program mode. It would also make an otherwise small cheap expansion very expensive.

That's right, if using a Flash it will need to contain a working Lower-ROM from the beginning.

But if it already has the regular lower ROM it is no problem to alter it. From the software side it will be no problem to exchange the lower ROM or parts of it.

So you would be easily able to replace the character set or patch the lower ROM just by using the connected CPC and you wouldn't require a PC to do that. You could even do it "in Game".

I know it is probably asked too much, but I like expansions that can be managed by the CPC itself without requiring an other computer. My philosophy in short: It needs a CPC, and it runs on/with the CPC ;-)

I would like a standalone board with 1MB flash chip shared for 512K RAM and 512K ROM (lower & upper)

Well, if you want a serious expansion: 4 MB RAM (compatible to RAM7 and Jareks expansions), should be in S-RAM, D-RAM, not Flash. Further 2 MB ROM (Flash). That's a good start. 0.5 MB is outdated and too small IMO.

Well the MegaFlash was designed to have 32 ROMs = 512K, not because 1MB was cheaper or whatever, but because more than 32 ROMs at one time on a CPC doesn't make sense.

That's right of course. However, one day in future I will finish my ROM disc and then it will make sense. But not 2011 though ;-)

[TFM]

In regards to another hardware project Bryce, did you ever make a batch of the PS2 mouse interface (http://www.cpcwiki.eu/index.php/PS2Mouse) or was it only a DIY project? I was also thinking if FutureOS can be placed at ROM 0 then the 2 may complement each other

Good idea!

[steve]

Is there is any need or opportunity for a community written enhanced/ faster firmware?
If so this might increase the number of people who would want a lower rom board.
What improvements are needed in the firmware?