iMac G3 (Rev A -> C) G4 CPU Upgrade

croissantking · Tuesday at 12:00 AM

indibil said:
I'm attaching the Wallstreet EEPROM file, and also the DA 466MHz EEPROM. Although it won't be of any use to us in this project, it might be useful to someone.

Do you think it's possible to modify something in the Wallstreet EEPROM to be able to work with a 2:1 ratio with the processor at 500MHz and the bus at 83MHz?

Thank you for providing these, I used the Wallstreet EEPROM on my heavily modded iMac/233 CPU board so it would recognise the full 1MB cache I'd soldered on.

Note the following findings for cache ratios:

CPU Speed (MHz)	Bus Speed (MHz)	Cache Ratio
300	66	2:1
300	100	3:2 (see photo)
350	100	2:1

indibil · Tuesday at 5:40 AM

croissantking said:
Thank you for providing these, I used the Wallstreet EEPROM on my heavily modded iMac/233 CPU board so it would recognise the full 1MB cache I'd soldered on.

Note the following findings for cache ratios:

CPU Speed (MHz) Bus Speed (MHz) Cache Ratio
300 66 2:1
300 100 3:2 (see photo)
350 100 2:1

View attachment 93518

Great!!

croissantking · Tuesday at 8:06 AM

indibil said:
Great!!

That your upload helped, or that the finding is useful?

In general, have we figured out how the ratio selection works? I’m guessing it would be possible to create a utility that calculates code for the EEPROM with options for cache size and ratio at a given clock speed.

iMac G3 (Rev A -> C) G4 CPU Upgrade

croissantking

indibil

croissantking

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