Forum Discussion

Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
13 years ago

what is the meaning of"cant place all ram cells in design"?

hi all: i make a project with quartus 11.1,and the chip is ep3c55f780c8. when i complie the design,an error occured.the message is"error(170040):cant place all ram cells in design".but the ram...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
13 years ago

On CIII devices, memory is fitted into M9k blocks.

With 32bit wide ram you can only use 8/9 of each block and you are not allowed to use spare bits elsewhere. This is a device constraint.

EP3C55 has 260 M9k blocks: each will be used in 256 x 32bit configuration, so you waste 256 x 4bits for each block. You need 256 blocks to synthesise your 2Mbit ram but you actually commit 2359296 physical memory bits.