cpc 464 eprom conversion , repairing an 464

[cuberdon]

And the newbie again , 


Confusion regarding replacing the 40009 rom for an eprom .

40009 is a 512k rom , so bios and firmware are in there 2 times 

Can a 27c256 eprom be used as a replacement or does it need to be a 27c512 ?



Regarding the diagnosis rom( s ) ,

can a lower ram and upper ram diagnostic version be integrated in one eprom , or do i need separate eproms for both ( 27c128 ).

[Bryce]

And the newbie again ,


Confusion regarding replacing the 40009 rom for an eprom .

40009 is a 512k rom , so bios and firmware are in there 2 times

Can a 27c256 eprom be used as a replacement or does it need to be a 27c512 ?



Regarding the diagnosis rom( s ) ,

can a lower ram and upper ram diagnostic version be integrated in one eprom , or do i need separate eproms for both ( 27c128 ).

Eh, nope. The 40009 is a 32k ROM and the Firmware and BASIC are only stored once in it. But yes, you can use a 27C256 as a drop in replacement.

Bryce.

[cuberdon]

Bryce , 

Thanks again , 

in goes the socket with the eprom .

[Bryce]

If you have a 27C512 spare, and you're adding a socket anyway, then you can always expand your CPC a little by doing this:  https://www.cpcwiki.eu/index.php/DualOS

Bryce.

[cuberdon]

firstly i need to get something else than a black screen ...........................

but i will modify the socket for multi-os .

[Bryce]

firstly i need to get something else than a black screen ...........................

but i will modify the socket for multi-os .

Ok, if the CPC already has issues, then start with a 27C256 with the correct image. Once you get it working you can decide if you want to expand it.

Bryce.

[cuberdon]

socket is in , and both a low-ram-diagnostic and a 40009 copy have been made .

now waiting for the new powersupply to give the board 5volt and see what the signals say on the scope .


-verified the original 40009 rom , and it has 2 sets of software in it 

[Bryce]

socket is in , and both a low-ram-diagnostic and a 40009 copy have been made .

now waiting for the new powersupply to give the board 5volt and see what the signals say on the scope .


-verified the original 40009 rom , and it has 2 sets of software in it

The 40009 should have the firmware in the first 16k and BASIC in the second 16k. The pin that would be A15 on a 27C512 is not connected to anything on the 40009 (ie: like a 27C256), but of course if you tell the EPROM reader that it's a 64k chip it will tell you that it found the same thing twice, but the chip is only 32k and definitely only has one copy stored in it.

Bryce.

[cuberdon]

Understood ;  firmware in first block , os in the second .


Re. dual os eprom , i assume the switch is used to switch between upper and lower 32 k ?
so 512 divided into 2 x 256 .

what leads me to the silly question about what firmware and os could be used in the 464 , or better said to make it an 6128 albeit without the correct amount of memory ......

[McArti0]

what leads me to the silly question about what firmware and os could be used in the 464 , or better said to make it an 6128

Of course firmware and os from 6128 

[cuberdon]

thus resulting in an 6128 in a 464 case , 

is there anything more to keep an eye on ?

sorry newbieeeeeeeeeeeeeeeeeeeeee , 40+ years ago a started the same way in the sinclair and commodore -world 

[cuberdon]

Anyway , 

Thank you everyone for your help !!

Eproms are burnt , i hope they will help me finding the next issue with this 464 .
Here i need your assistance a bit more .


This subject is closed , i go on with the black-screen thread .