CPC6128 ROM chip

Fran123 · 13:19, 04 January 25

Hello

I read the ROM chip is a 27128 (https://downloads.reactivemicro.com/Electronics/ROM/27128%20EPROM.pdf) that has only 14 pins for address, then, how can it distinguish when to use the lower rom or the upper rom?

Thanks

Bryce · 13:32, 04 January 25

Quote from: Fran123 on 13:19, 04 January 25Hello

I read the ROM chip is a 27128 (https://downloads.reactivemicro.com/Electronics/ROM/27128%20EPROM.pdf) that has only 14 pins for address, then, how can it distinguish when to use the lower rom or the upper rom?

Thanks

Not sure where you read that, but it's wrong. ROM7 (AMSDOS) is a 27C128, but the Firmware/Basic EPROM is a 27C256.

Bryce.

Fran123 · 13:38, 04 January 25

They are similar. Both have the same pinout (https://ww1.microchip.com/downloads/en/devicedoc/11003L.pdf)

Fran123 · 14:05, 04 January 25

I was wrong

. That chip is used in 464 model, it has only 16 kb and 14 pins for address. 6128 uses the 27C256 rom chip, that it has 32kb and 15 pins.

Bryce · 15:34, 04 January 25

Quote from: Fran123 on 14:05, 04 January 25I was wrong . That chip is used in 464 model, it has only 16 kb and 14 pins for address. 6128 uses the 27C256 rom chip, that it has 32kb and 15 pins.

Still not quite right: The 464 has a 27C256 (Firmware and Basic) and the 6128 has a 27C256 (Firmware and Basic) and a 27C128 (AMSDOS).

Bryce.

Fran123 · 18:27, 07 January 25

But... CPC6128 has three ROMS: firmware, BASIC and AMSDOS. Does it use a different chip?

robcfg · 19:17, 07 January 25

Firmware and Basic go together in one 27C256 chip and AmsDOS goes into a 27C128 chip.

Roms are 16KB in size thus in a 27C256 chip (32KB) there's room for two of them, while on a 27C128 there's room for only one.

So, these two chips hold three different roms.

GUNHED · 21:32, 07 January 25

btw... No EPROMs are used for firmware + BASIC, it's an 32 KB PROM.

robcfg · 23:40, 07 January 25

That's correct, but if you need to replace them or use your own, you'll need equivalent EPROMS, which are the ones mentioned

Bryce · 23:58, 07 January 25

Quote from: Fran123 on 18:27, 07 January 25But... CPC6128 has three ROMS: firmware, BASIC and AMSDOS. Does it use a different chip?

Really? Show me a 6128 PCB with three ROM's on the board.

[/quote]

Quote from: Bryce on 15:34, 04 January 25Still not quite right: The 464 has a 27C256 (Firmware and Basic) and the 6128 has a 27C256 (Firmware and Basic) and a 27C128 (AMSDOS).

Bryce.

Bryce.

GUNHED · 15:32, 08 January 25

Quote from: robcfg on 23:40, 07 January 25That's correct, but if you need to replace them or use your own, you'll need equivalent EPROMS, which are the ones mentioned

Yep! Or some external (Flash-)ROM expansion or the M4, or the SF3, or ... that's for another topic

eto · 15:42, 08 January 25

Quote from: Fran123 on 18:27, 07 January 25But... CPC6128 has three ROMS: firmware, BASIC and AMSDOS. Does it use a different chip?

3 ROMS but only 2 ICs

1) Firmware + BASIC are in one 32KB chip together (in all CPC models). The first 16K are the firmware, the upper 16K are BASIC. You can use a 27C256 Eprom to burn a replacement.

2) AMSDOS in 664 and 6128 has its own 16KB chip. You can use a a 27C128 Eprom to burn a replacement.

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CPC6128 ROM chip