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A2088 XT Bridge Board

A2088 Upgrades and modifications

A2088 Upgrade ROM

A new ROM revision has been issued to upgrade the A2088.
ROM - U28 - Part Number - 380788-06
This ROM fixes Auto-Configuration errors caused by some third part software and hardware.
This is an in-line change and is not covered under standard warranty. Dealer billing is $7.70.

Source: Commodore Techtopics 27/3-7.1 and 28/3-4.1

A2088 use external 1020 as drive A:

A2088 XT Emulator is configured to see the internal 5 1/4 drive as drive A:. Some customers are requesting that an external 5 1/4 be configured as drive A:. To modify the A2088 you must reverse the drive select signals .

Remove the A2088 Bridge card from unit. Locate IC U49 (74LS175), see page 26 in A2000 System Schematics.
Note: Pin 10 (*DRVSEL1) is tied to pin 1 of U44 (7406) and pin 15 (*DRVSEL2) is tied to pin 3 of U44.

On bottom side (trace side) of PCB cut traces on pins 10 and 15 of U49. Solder a jumper wire from pin 10 of U49 to pin 3 of U44. Solder second jumper from U15 of U49 to pin 1 of U44. External 1020 will now be configured as drive A: and internal 5 1/4 will be configured as drive B:.

Note: This modification is done at the customer's request, and will void the warranty on the A2088. Commodore will not assume any liability for this modification and no credit will be given for PCB's retured which have this modification.

Source: Commodore Techtopics 19/3-4.1

A2088 Parts List

Integrated Circuits
PositionDescriptionPart numberNotes
U40Address Bus Translator380658-01
U41Data Bus Translator 5718380659-01
U29PAL RAM Decoder Emulator380783-01Produced of 16L8; PN-380219-01
U50PAL I/O Decoder380784-01Produced of 16L8; PN-380219-01
U39PAL Configuration380785-01Only used if jumper JA1 open
U7FE 2010380786-01Vendor: Faraday
U12..U27DRAM 256k X 1, 150 ns380223-01
U32..U35DRAM 64k X 4, 150 ns380256-01
U42FDC 9268380787-01Vendor: SMC
U28BIOS PC-Emulator380788-01Produced of 27128 EPROM or ROM 23128 TAC = 250 ns
U10, U1174 HCT 158380227-04
U36, U3774 HCT 257380227-58
U43, U447406901522-06
U4574 LS 08901521-03
U4674 LS 14901521-30
U4774 LS 125901521-20
U3874 LS 133901521-15
U4874 LS 164901521-28
U4974 LS 175901521-34
U8, U974 LS 244901521-13
U3, U30, U5174 LS 245901521-46
U4..U674 LS 373901521-29
U31Digital Delay Line324667-01

A2088 Connectors and jumpers

Connectors and jumpers
J12x3 pin header (903345-03)Default display jumperMonochrome: 3-5 + 4-6, Color 40x25: 3-5 + 2-4, Color 80x25: 1-3 + 4-6, None: 1-3 + 2-4
J21x2 pin header (903326-02)Speaker
J32x17 pin header (903345-17)Internal Floppy Disk A:Pin 3 removed at assembly
J423 pin SUB-D female (327033-01, 310975-01)External Floppy Disk B:Amiga-compatible
J52x50 cardedgeAmiga 2000 bus
J62x31 cardedgePC bus
J71x8 pin header (903326-08)Test connectorPin 6 removed at assembly
JA1Wire jumper (903781-01)
JA2Wire jumper (903781-01)

Copyright © 2007 Ronald van Dijk - All rights reserved
Last update: 26 February 2012
Source: System Schematics A2000 PN-314135-01 August, 1990 © 1990 Commodore Electronics Limited