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A Trip Down
Memory Lane
Matt Jenkins <mdj@emdeejay.net>
Monday, 29 July 13
RAM and the Apple II
• Static and Dynamic types
• Static RAM an array of flip-flops (latches)
• Dynamic RAM an array of capa...
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
Or...
RAM and the Apple II
Apple II memory map
48k
I/O
ROM
$0000
$BFFF
$C000
$CFFF
$D000
$FFFF
Monday, 29 July 13
RAM and the Apple II
• Designed for Apple Pascal
• Adds 16k more RAM
• Bank switched to overlay ROM area
The Language Syst...
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
Ove...
RAM and the Apple II
• Saturn Systems 64k and 128k Cards
• Just like having 4 or 8 Language Cards
• Register controls whic...
RAM and the Apple IIe
• RAM gets cheaper, move to 64k DRAM
• Language Card built in
• Optional Auxiliary 64k RAM
Monday, 2...
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 $D00...
RAM and the Apple IIe
• Multibank Auxiliary Cards Appear
• 256k DRAM becomes affordable
• Applied Engineering RAMWorks
Thi...
The RamWorks Card
• Bank Select Register allows 256 banks
• (in theory) 16MB is possible
• 1MB of RAM on Board
• Daughter ...
The RamWorks Card
• Can be used as RamDisk
• Extends the AppleWorks Desktop
• Print buffering
• Most “power” applications ...
The RamWorks Card
• Apple went another way (Slinky)
• Tricky to program for
• Getting hard to find
• Extender cards unobtai...
Alternatives
• Apple II Memory Expansion Card (Slinky)
• Provides extra RAM as secondary storage
• Essentially a RAMDisk c...
Today
• Can we recreate the RamWorks ?
• DRAM or SRAM ?
• Just how much RAM can we add ?
Monday, 29 July 13
SRAM
• Cypress CY62167ELL-45ZXI
• Can run at 5V
• 16mbit configurable as 2mb x 8
• TSOP-48 package
• 2.2mA at 1Mhz
• Afford...
Auxiliary Slot
• Address bus multiplexed
• Borrows motherboard RAM refresh
• No access to IO areas
• C07x strobe is availa...
SRAM Card
AUX
Slot
Multiplexed
Address Bus
Address
DeMux
Data Bus
Bank
Select
Register
Decoded 24 bit
Address
Video Data B...
SRAM Card
• 7400 series logic all we need
• 74HCT simplifies design
• Test socket for SRAM
• Only 8 chips required
• Easily...
ScramWorks I
• Static RAM
• CMOS Design
• Replaces RamWorks
Monday, 29 July 13
The Future
• Prototype PCB
• More testing
• Does anyone want one ?
• Replicate RamWorks daughtercard ports ?
• Possible mo...
Questions ?
Monday, 29 July 13
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A trip down memory lane

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Slides from the presentation of my "Scramworks" prototype Ramworks compatible memory card for the Apple IIe

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A trip down memory lane

  1. 1. A Trip Down Memory Lane Matt Jenkins <mdj@emdeejay.net> Monday, 29 July 13
  2. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 15. Today • Can we recreate the RamWorks ? • DRAM or SRAM ? • Just how much RAM can we add ? Monday, 29 July 13
  16. 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. 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. 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. 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. 20. ScramWorks I • Static RAM • CMOS Design • Replaces RamWorks Monday, 29 July 13
  21. 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. 22. Questions ? Monday, 29 July 13

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