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Apple IIGS Memory Expansion Card

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Apple IIGS Memory Expansion Card
The 256K card as shipped: eight soldered DRAMs at UA1-UA8 and 24 empty sockets (owner's guide cover)
Manufacturer Apple Computer
Type RAM expansion card
Interface Apple IIGS memory expansion slot
Compatible Apple IIGS; Apple IIe with the Apple IIGS Upgrade
Model A2B6002
Power +5 V; 200 mA operating at 256K, 600 mA at 1 MB
Part number 670-0025 (board)

The Apple IIGS Memory Expansion Card is Apple's RAM card for the memory expansion slot of the Apple IIGS. It came with 256K and could be filled to 512K or 1 MB in 256K steps with Apple 256K Memory Expansion Kits.[1] Apple's order number for the card was A2B6002.[1] Its owner's guide is dated 1986.[2] See Apple II Memory Expansion Cards Documentation for the manuals.

Apple IIGS Memory Expansion Card configurations
Size RAM fitted Jumpers
256K UA1-UA8, soldered None
512K UA1-UA16 J2
1 MB UA1-UA16 and UB1-UB16 J1 and J2

Apple's service manual gives the chip positions and jumpers.[3] The owner's guide describes the same thing as one jumper block on the lower set of pins for 512K and blocks on both sets for 1 MB.[2]

Memory map

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The card's RAM extends the IIGS's own memory: Apple's data sheet says it is "addressed linearly",[1] and applications written for the IIGS use it automatically.[2] The IIGS hardware reference describes the slot as taking up to 4 MB of RAM in four rows of eight chips. With 256K-bit chips each row is 256K, so the Apple card's 1 MB is the full four rows.[4]

A partly filled card leaves holes in the memory map. On the original 256K IIGS, only 256K, 512K and 1 MB cards give contiguous memory; 768K does not.[4] Apple's owner's guide and data sheet both advise against 768K because some programs cannot handle it.[2][1] Apple's Tech Info Library adds that a 768K card causes memory "ghosting", where addressing an empty upper bank returns a lower bank, and leaves gaps that can confuse the Memory Manager.[5]

Apple's figures for the total system RAM with a full card are 1.25 MB on a ROM 01 machine (256K on the board) and 2 MB on a ROM 03 machine (1 MB on the board).[6]

Part of the card's memory can be set aside as a RAM disk from the RAM disk screen of the Control Panel, with a minimum and a maximum size. The RAM disk appears to programs as a drive in slot 5, ahead of the 3.5-inch drives, and loses its contents when the power goes off. With ProDOS versions earlier than 1.2 the minimum and maximum must be set to the same value.[2]

RAM chips

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The card takes 256K × 1 dynamic RAMs, 150 ns or faster, with CAS-before-RAS refresh. Apple's own part was 334-0021. Apple's Tech Info Library lists compatible parts from Fujitsu (MB81256-15), NEC (UPD41256C-15), Texas Instruments (TMS4256-15NL), Mitsubishi (M5M4256AP-15), Hitachi (HM50256P-15), OKI (M41256-15), Micron (MT1259-15), Samsung (KM41256AP-15), Motorola (MCM6256BP-15) and Toshiba (TMM41256P-15), and warns that chips outside the specification cause crashes, lock-ups and memory errors.[7] There is no way to tell from the package whether a chip has CAS-before-RAS refresh, so specify it when buying.[3]

Each Apple 256K Memory Expansion Kit held eight chips. Fit them with the notched end pointing down, and straighten splayed pins by rolling the chip on its side on a flat surface before inserting it.[2] Owners today use 41256-type chips, often salvaged from old PC memory cards.[8]

Installing

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  1. Switch the IIGS off but leave it plugged into an earthed socket, then wait at least 30 seconds.[2]
  2. Remove the lid: hold the latches in at the rear corners and push the lid up.
  3. Touch the power supply case to discharge static.
  4. Fit any extra RAM chips and the jumper blocks before installing the card (see the table above).
  5. Press the card into the memory expansion slot, rocking it from front to back until it seats. Do not wiggle it from side to side.
  6. Refit the lid, then hold Option while switching on to enter the Control Panel. Under RAM disk, the "Largest selectable" figure should match the memory on the card.[2] On an Apple IIe with the IIGS upgrade, hold Control and Closed-Apple and press Reset at power-on instead.[3]

Apple's service manual says the memory expansion slot is designed only for the Apple IIGS Memory Expansion Card, and that no other card should go in it unless its maker says so.[3]

Faults

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Apple IIGS Memory Expansion Card faults
Symptom Likely cause Action
Random crashes or lock-ups RAM that does not meet Apple's specification. Apple found some of its own NEC chips lacked CAS-before-RAS refresh: those stamped "UK" under the NEC name, and those stamped "Japan" with P as the first letter of the date code (the fifth character) Replace the socketed RAM with chips that meet the specification. If the bad RAM is soldered, Apple replaced the card[3]
Wrong size under RAM disk in the Control Panel, or "out of RAM" errors Missing or wrong jumper, chips in the wrong sockets, a faulty chip, or a RAM disk taking the memory Check the jumpers against the table, check for a RAM disk set in the Control Panel, and run the diagnostics[9][2]
Diagnostic lists chip positions Faulty socketed RAM Replace the chips named (UA9-UA16, UB1-UB16) and retest[3]
Diagnostic shows "Soldered IC's" Faulty soldered RAM at UA1-UA8 Apple exchanged the card[3]
Diagnostic shows "Out of Spec IC(s)" A chip without CAS-before-RAS refresh or too slow Replace the chips named[3]

Apple's test for the card is on the Apple II Diagnostic Disk, in the RAM Tests folder, and takes 10 to 15 minutes.[3]

Other memory cards in the IIGS

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An Apple II Memory Expansion Card in one of the IIGS's seven peripheral slots does not add to the IIGS's memory. GS/OS and ProDOS treat it as a RAM disk, named after its slot (/RAM4 in slot 4).[10][11]

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References

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  1. ↑ 1.0 1.1 1.2 1.3 Apple Computer, Apple II Memory Expansion Cards data sheet, July 1987, A2F2222, pp. 53-56. Hosted as File:Apple II Memory Expansion Cards data sheet (A2F2222, July 1987).pdf. Source for: 256K standard, expandable to 1 MB in 256K steps (p. 53); 768K not recommended on the IIGS, dealer configuration recommended, memory addressed linearly (p. 54); power consumption (p. 55); order numbers A2B6002 (card) and A2M2058 (Apple 256K Memory Expansion Kit), one kit for 512K and three for 1 MB (p. 56).
  2. ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 Apple Computer, Apple IIGS Memory Expansion Card Owner's Guide, 030-1310-B, © 1986. Hosted as File:Apple IIGS Memory Expansion Card Owner's Guide (030-1310-B, 1986).pdf. Introduction (p. v): adds 256K, 512K or 1 MB; each Apple 256K memory expansion kit adds 256K. Chapter 1 (pp. 1-2): installation. Chapter 2 (pp. 3-9): RAM disk. Chapter 3 (pp. 11-13): upgrading, jumper blocks and chip installation; 768K "not a good idea".
  3. ↑ 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 Apple Computer, Apple Service Technical Procedures, Apple II Family, Volume One, PN 072-0229 (March 1992), Apple IIGS section: Diagnostics pp. 3.14-3.15 (Apple IIGS Memory Expansion Card Test, 10 to 15 minutes; failure types; UA1-UA16 and UB1-UB16 markings, UA1-UA8 not replaceable; "Soldered IC's" and "Out of Spec IC(s)" messages); Troubleshooting p. 4.3 (the memory expansion slot is designed only for the Apple IIGS Memory Expansion Card; Control Panel access on an upgraded Apple IIe with Control, Closed-Apple and Reset) and p. 4.8 (random crashes or lock-ups; NEC RAM that does not meet the CAS-before-RAS requirement); Additional Procedures pp. 5.4-5.6 (RAM specification; 256K, 512K and 1 MB configurations with jumpers J1 and J2; board 670-0025; exchange modules shipped without socketed RAM; cards with all RAM soldered). Archive.org item Apple_Service_Technical_Procedures_Apple_II_Family_Volume_One_1992-03_Apple_PN_072-0229, https://archive.org/details/Apple_Service_Technical_Procedures_Apple_II_Family_Volume_One_1992-03_Apple_PN_072-0229 (retrieved 2026-10-04).
  4. ↑ 4.0 4.1 Apple IIGS Hardware Reference, second edition, Apple Computer, 1989, Chapter 3 "Memory", "Memory expansion" to "Address multiplexing", pp. 49-54: 4 MB RAM and 768K ROM on a card; Table 3-4, memory-card interface signals, +5 V ±5 per cent, 600 mA maximum; four rows of eight ICs; ghost addresses and holes in the memory map with partly filled cards; 256K, 512K and 1 MB cards give contiguous memory on the 256K IIGS; the MSIZE signal. Hosted as File:Apple IIGS Hardware Reference 1989.pdf (see Apple IIGS Hardware Reference).
  5. ↑ Apple Computer, Tech Info Library article 1135, Apple IIGS Memory Expansion Card: Don't Set It to 768K (10/94), created 12 November 1987, absurdengineering.org library. Cites the card's manual (030-1310-A), chapter 3, p. 11; memory ghosting and gaps in the memory map with 768K.
  6. ↑ Apple Computer, Tech Info Library article 7894, IIGS Memory Expansion Card: Description (11/96), created 31 May 1991, absurdengineering.org library. Up to 1 MB in 256K increments; total RAM 1.25 MB with ROM 01 or 2 MB with ROM 03; requires an Apple IIGS or an Apple IIe with the Apple IIGS Upgrade; 4.75-5.25 V; 200 mA operating and 140 mA standby at 256K, 600 mA and 370 mA at 1 MB.
  7. ↑ Apple Computer, Tech Info Library article 2668, Apple IIGS Memory Expansion Cards: RAM Chip Specs & Vendors, created 22 March 1988, updated 9 February 1993, absurdengineering.org library. 150 ns, 256K × 1, CAS-before-RAS refresh; Apple part 334-0021; the vendor list.
  8. ↑ Applefritter forum, "What memory do I buy to upgrade my base Apple iigs memory expansion?", June 2014, https://www.applefritter.com/content/what-memory-do-i-buy-upgrade-my-base-apple-iigs-memory-expansion (retrieved 2026-10-04). Replies by dorkbert: 41256 (256K × 1) DIP DRAMs, often salvaged from old PC ISA memory cards, Fujitsu MB81256-15 as an equivalent; the asker's card is a 256K 670-0025.
  9. ↑ Apple Computer, Tech Info Library article 8150, Apple IIGS: Troubleshooting Out of RAM 04 Message, 14 May 1991, absurdengineering.org library. GS/OS boots in 512K and needs 768K for network services; check for a RAM disk; faulty RAM on the board or card; the card misreading its jumpers.
  10. ↑ Apple Computer, Tech Info Library article 8232, Apple IIGS: Contiguous RAM Depends on Memory Board, 14 May 1991, absurdengineering.org library. The Apple II Memory Expansion Card in slots 1-7 is not contiguous RAM; GS/OS and ProDOS make it a RAM disk at startup.
  11. ↑ Apple Computer, Tech Info Library article 611, Apple II Memory Expansion Card: Using it on the Apple IIGS, last reviewed 14 September 1987, absurdengineering.org library. The card appears as a volume named after its slot, such as /RAM4.


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