CPC iRAM

CPC iRAM is a series of open source, DIY friendly, internal RAM expansions for the CPC 6128 and CPC 464/664 (later hopefully also for the Plus/GX4000).

The iRAM expansion sits in the CPU socket and requires no additional soldering inside the CPC.

Compatibility

So far no incompatibilities have been reported.

The first 512K of expansion RAM follow the DK'Tronics addressing mode standard, giving up to 576K of RAM to legacy software. More modern software that supports the extended 1M-4M standard will be able to access all the provided RAM.

Unlike other RAM expansions the iRAM can be used in parallel to an external RAM expansion. The iRAM has priority over external RAM expansions and only requests above the iRAM memory limit will be passed to an external RAM expansion. External memory expansions that are smaller than the iRAM will be ignored. This is particularly helpful for external feature-expansions that also provide a RAM expansion. Those expansions usually cannot be connected in parallel to another (bigger) RAM expansion. E.g. DDI-5/6, ULIFAC and Pico CPC limit the CPC to the RAM provided by those expansions. A great use case is to put the ULIFAC in ROM board mode which limits the RAM to 192 or 256K - but with the iRAM installed the CPC still has access to the full RAM provided by the iRAM.

released

CPC 6128 - iRAM/640

• 

  iRAM/640

• 

  iRAM/640 built-in

• 

  RAM Test

• for CPC 6128 only
• 512K expansion
• total accessible RAM of 640K in a 6128 (64K Base RAM + 512K RAM expansion + 64K secondary RAM bank of the 6128)
• easy to assemble, all through-hole components
• perfectly fits into a CPC 6128, even with socketed ROM or RAM. In Schneider CPC 6128 the metal shielding needs to be removed or altered.

Status: Released - see https://github.com/etomuc/CPC6128_iRAM-640

CPC 6128 - iRAM/1088

• 

  iRAM/1088 for CPC 6128

• for CPC 6128 only
• 1024K expansion
• total accessible RAM of 1088K in a 6128 (64K Base RAM + 1024K RAM expansion)
• easy to assemble, but SRAMs are in SMD packaging (SOP32) due to size constraints in the CPC 6128
• perfectly fits into a CPC 6128, even with socketed ROM or RAM. In Schneider CPC 6128 the metal shielding needs to be removed or altered.

Status: Released - see https://github.com/etomuc/CPC6128_iRAM-1088

currently in development

CPC 464/664 - iRAM/1024

• 

  iRAM/1024 for CPC 464/664

• 

  SymbOS on CPC 464

• for CPC 464 and 664
• offers two sockets for SRAMs
• upgrade to 576K (1 SRAM) or 640K/1024K (2 SRAMS)
• first SRAM: Upgrade to 576K, following the DK'Tronics standard without support of C3 mode (like many other RAM expansions)
• second SRAM: upgrade to 1024K (512K SRAM) or optionally also 640K (128K SRAM)
• C3 RAM banking supported if both SRAMs are fitted
• easy to assemble, all through-hole components

Status: Finished, final PCB design will be tested, will be released in late 2025

considered

PLUS iRAM/1024

• 1Mb upgrade for Plus series
• less DIY friendly, probably needs more complex CPLDs (ATF1504)

Status: very early stage, still considering if it's feasible

GX iRAM/512

• 512K upgrade for GX4000
• less DIY friendly, probably needs more complex CPLDs (ATF1504)

Status: just an idea

abandoned

CPC 6128 - iRAM/640s

• minified iRAM/640
• for CPC 6128
• size just a tiny bit bigger than Z80 CPU socket
• TSSOP SMD components below Z80
• requires good soldering skills and special tools to program SMD CPLDs

Status: fully designed, abandoned as it offers no advantage over DIY friendly version and would only benefit commercial sellers (Hint: Lotharek offers a similar expansion commercially for a good price)

CPC 464/664 - iRAM/1024s

• smaller than iRAM/1024, more similar in size to iRAM/640
• for CPC 464 and 664
• single 1MB SMD SRAM, upgrade to 1024K
• C3 RAM banking supported
• easy to assemble, mostly through-hole components but one SMD SRAM

Status: working prototype

CPC 6128 - iRAM/576

• for CPC 6128 only
• 512K expansion
• total accessible RAM of 576K in a 6128 (following the DK'Tronics standard)
• easy to assemble, all through-hole components

Status: Abandoned in favor of the iRAM/640 which uses the exact same components but offers more total memory.

CPC 464/664 - iRAM/512

• for CPC 464/664
• 512K expansion
• total accessible RAM of 512K in a CPC, following the DK'Tronics standard and support of C3 mode.
• or 576K without C3 support (512K_C3 / 576K selection per manual switch)
• easy to assemble, all through-hole components

Status: Abandoned as CPC iRAM/1024 will fit into all 464s/664s and is more flexible