A trip down memory lane

1. A Trip Down Memory Lane Matt Jenkins <mdj@emdeejay.net> Monday, 29 July 13

2. RAM and the Apple II • Static and Dynamic types • Static RAM an array of ﬂip-ﬂops (latches) • Dynamic RAM an array of capacitors • SRAM faster, less dense, more power • DRAM denser, slower, requires refresh Monday, 29 July 13

3. RAM and the Apple II • Supported two types of DRAM chip • 3 banks of 8 chips • 4kbit or 16kbit DRAMs for a total of 48k Original Apple II/II+ Monday, 29 July 13

4. RAM and the Apple II Apple II memory map 48k I/O ROM $0000 $BFFF $C000 $CFFF $D000 $FFFF Monday, 29 July 13

5. RAM and the Apple II • Designed for Apple Pascal • Adds 16k more RAM • Bank switched to overlay ROM area The Language System Monday, 29 July 13

6. RAM and the Apple II RAM 48k I/O ROM 12k $0000 $BFFF $C000 $CFFF $D000 $FFFF 8k 4k Bank4k Bank $D000-$DFFF $E000 $FFFF Overlays ROM 16k Language Card Motherboard RAM and ROM Monday, 29 July 13

7. RAM and the Apple II • Saturn Systems 64k and 128k Cards • Just like having 4 or 8 Language Cards • Register controls which is active Third Party Extensions Monday, 29 July 13

8. RAM and the Apple IIe • RAM gets cheaper, move to 64k DRAM • Language Card built in • Optional Auxiliary 64k RAM Monday, 29 July 13

9. RAM and the Apple IIe 8k 4k Bank4k Bank $D000-$DFFF $E000 $FFFF RAM 48k I/O $0000 $BFFF $C000 $CFFF 8k 4k Bank4k Bank $D000-$DFFF $E000 $FFFF RAM 48k I/O $0000 $BFFF $C000 $CFFF Main Memory Auxiliary Memory Switches with zero page Switchable reads and writes Monday, 29 July 13

10. RAM and the Apple IIe • Multibank Auxiliary Cards Appear • 256k DRAM becomes affordable • Applied Engineering RAMWorks Third Party Extensions Monday, 29 July 13

11. The RamWorks Card • Bank Select Register allows 256 banks • (in theory) 16MB is possible • 1MB of RAM on Board • Daughter Cards allow extension to 3MB • RGB video and 65816 processor options Monday, 29 July 13

12. The RamWorks Card • Can be used as RamDisk • Extends the AppleWorks Desktop • Print buffering • Most “power” applications can use it • Adds real RAM Advantages Monday, 29 July 13

13. The RamWorks Card • Apple went another way (Slinky) • Tricky to program for • Getting hard to ﬁnd • Extender cards unobtainium • Only really useful for programmers Disadvantages Monday, 29 July 13

14. Alternatives • Apple II Memory Expansion Card (Slinky) • Provides extra RAM as secondary storage • Essentially a RAMDisk card • Can’t directly address the RAM • Somewhat pointless when fast secondary storage available. Monday, 29 July 13

15. Today • Can we recreate the RamWorks ? • DRAM or SRAM ? • Just how much RAM can we add ? Monday, 29 July 13

16. SRAM • Cypress CY62167ELL-45ZXI • Can run at 5V • 16mbit conﬁgurable as 2mb x 8 • TSOP-48 package • 2.2mA at 1Mhz • Affordable Monday, 29 July 13

17. Auxiliary Slot • Address bus multiplexed • Borrows motherboard RAM refresh • No access to IO areas • C07x strobe is available • Other signals for video expansion Monday, 29 July 13

18. SRAM Card AUX Slot Multiplexed Address Bus Address DeMux Data Bus Bank Select Register Decoded 24 bit Address Video Data Bus Static RAM Upper 8 bits of address disabled during video fetch (PH1) Upper 8 bits of address enabled during CPU fetch (PH0) Monday, 29 July 13

19. SRAM Card • 7400 series logic all we need • 74HCT simpliﬁes design • Test socket for SRAM • Only 8 chips required • Easily assembled on a Breadboard Monday, 29 July 13

20. ScramWorks I • Static RAM • CMOS Design • Replaces RamWorks Monday, 29 July 13

21. The Future • Prototype PCB • More testing • Does anyone want one ? • Replicate RamWorks daughtercard ports ? • Possible move to low voltage large SRAMs • BGA tough to work with Monday, 29 July 13

22. Questions ? Monday, 29 July 13

A trip down memory lane

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A trip down memory lane

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