diff --git a/README.md b/README.md
index 57a1b6f2..59398f72 100644
--- a/README.md
+++ b/README.md
@@ -95,7 +95,7 @@ In addition, Stella was used as reference in the following areas:
 * During the development of the CDF cartridge formats. These recent formats don't
 seem to be documented anywhere accept in the Stella source.
 
-* Cartridge fingerprints for ParkerBros, Wickstead Design and SCABS.
+* Cartridge fingerprints for ParkerBros, Wickstead Design, SCABS and UA.
 
 * As a reference for the audio implementation (the 6502.ts project was also
   referenced for this reason).
diff --git a/cartridgeloader/extensions.go b/cartridgeloader/extensions.go
index c21487ea..a79dbef1 100644
--- a/cartridgeloader/extensions.go
+++ b/cartridgeloader/extensions.go
@@ -18,8 +18,9 @@ package cartridgeloader
 // FileExtensions is the list of file extensions that are recognised by the
 // cartridgeloader package.
 var FileExtensions = [...]string{
-	".BIN", ".ROM", ".A26", ".2K", ".4K", ".F8", ".F6",
-	".F4", ".2K+", ".2KSC", ".4K+", ".4KSC", ".F8+", ".F8SC", ".F6+", ".F6SC", ".F4+", ".F4SC",
-	".FA", ".FE", ".E0", ".E7", ".3F", ".AR", ".DF", "3E", "3E+", "SB",
-	".DPC", ".DP+", "CDF", ".WAV", ".MP3", ".MVC",
+	".BIN", ".ROM", ".A26", ".2K", ".4K", ".F8", ".F6", ".F4", ".2K+", ".2KSC",
+	".4K+", ".4KSC", ".F8+", ".F8SC", ".F6+", ".F6SC", ".F4+", ".F4SC", ".CV",
+	".FA", ".FE", ".E0", ".E7", ".3F", ".UA", ".AR", ".DF", ".3E", ".E3P",
+	".E3+", ".3E+", ".EF", ".EFSC", ".SB", ".WD", ".ACE", ".CDF0", ".CDF1", ".CDFJ",
+	".CDFJ+", ".DP+", ".DPC", ".CDF", ".WAV", ".MP3", ".MVC",
 }
diff --git a/cartridgeloader/loader.go b/cartridgeloader/loader.go
index fc2562e8..ae95cb31 100644
--- a/cartridgeloader/loader.go
+++ b/cartridgeloader/loader.go
@@ -200,6 +200,8 @@ func NewLoader(filename string, mapping string) (Loader, error) {
 			fallthrough
 		case ".3F":
 			fallthrough
+		case ".UA":
+			fallthrough
 		case ".AR":
 			fallthrough
 		case ".DF":
diff --git a/hardware/memory/cartridge/cartridge.go b/hardware/memory/cartridge/cartridge.go
index 93600af4..d45d0b12 100644
--- a/hardware/memory/cartridge/cartridge.go
+++ b/hardware/memory/cartridge/cartridge.go
@@ -299,6 +299,8 @@ func (cart *Cartridge) Attach(cartload cartridgeloader.Loader) error {
 		cart.mapper, err = newMnetwork(cart.env, *cartload.Data)
 	case "3F":
 		cart.mapper, err = newTigervision(cart.env, *cartload.Data)
+	case "UA":
+		cart.mapper, err = newUA(cart.env, *cartload.Data)
 	case "AR":
 		cart.mapper, err = supercharger.NewSupercharger(cart.env, cartload)
 	case "DF":
diff --git a/hardware/memory/cartridge/fingerprint.go b/hardware/memory/cartridge/fingerprint.go
index 2d204676..252c660b 100644
--- a/hardware/memory/cartridge/fingerprint.go
+++ b/hardware/memory/cartridge/fingerprint.go
@@ -214,6 +214,24 @@ func fingerprintSCABS(b []byte) bool {
 	return false
 }
 
+func fingerprintUA(b []byte) bool {
+	// ua fingerprint taken from Stella
+	fingerprint := [][]byte{
+		{0x8D, 0x40, 0x02}, // STA $240 (Funky Fish, Pleiades)
+		{0xAD, 0x40, 0x02}, // LDA $240 (???)
+		{0xBD, 0x1F, 0x02}, // LDA $21F,X (Gingerbread Man)
+		{0x2C, 0xC0, 0x02}, // BIT $2C0 (Time Pilot)
+		{0x8D, 0xC0, 0x02}, // STA $2C0 (Fathom, Vanguard)
+		{0xAD, 0xC0, 0x02}, // LDA $2C0 (Mickey)
+	}
+	for _, f := range fingerprint {
+		if bytes.Contains(b, f) {
+			return true
+		}
+	}
+	return false
+}
+
 func fingerprintDPCplus(b []byte) bool {
 	if len(b) < 0x23 {
 		return false
@@ -301,6 +319,10 @@ func fingerprint8k(data []byte) func(*environment.Environment, []byte) (mapper.C
 		return newSCABS
 	}
 
+	if fingerprintUA(data) {
+		return newUA
+	}
+
 	return newAtari8k
 }
 
diff --git a/hardware/memory/cartridge/mapper_atari.go b/hardware/memory/cartridge/mapper_atari.go
index 020f1bf8..d5e59291 100644
--- a/hardware/memory/cartridge/mapper_atari.go
+++ b/hardware/memory/cartridge/mapper_atari.go
@@ -195,8 +195,8 @@ func (cart *atari) access(addr uint16) (uint8, uint8, bool) {
 	return 0, mapper.CartDrivenPins, false
 }
 
-// accessDriven implements the mapper.CartMapper interface.
-func (cart *atari) accessDriven(addr uint16, data uint8, poke bool) error {
+// accessVolatile implements the mapper.CartMapper interface.
+func (cart *atari) accessVolatile(addr uint16, data uint8, poke bool) error {
 	if cart.state.ram != nil {
 		if addr <= 0x7f {
 			cart.state.ram[addr] = data
@@ -335,7 +335,7 @@ func (cart *atari4k) Access(addr uint16, peek bool) (uint8, uint8, error) {
 
 // AccessVolatile implements the mapper.CartMapper interface.
 func (cart *atari4k) AccessVolatile(addr uint16, data uint8, poke bool) error {
-	return cart.atari.accessDriven(addr, data, poke)
+	return cart.atari.accessVolatile(addr, data, poke)
 }
 
 // atari2k is the half-size cartridge of 2048 bytes:
@@ -411,7 +411,7 @@ func (cart *atari2k) CopyBanks() []mapper.BankContent {
 
 // AccessVolatile implements the mapper.CartMapper interface.
 func (cart *atari2k) AccessVolatile(addr uint16, data uint8, poke bool) error {
-	return cart.atari.accessDriven(addr, data, poke)
+	return cart.atari.accessVolatile(addr, data, poke)
 }
 
 // atari8k (F8):
@@ -482,7 +482,7 @@ func (cart *atari8k) AccessVolatile(addr uint16, data uint8, poke bool) error {
 		}
 	}
 
-	return cart.atari.accessDriven(addr, data, poke)
+	return cart.atari.accessVolatile(addr, data, poke)
 }
 
 // bankswitch on hotspot access.
@@ -580,7 +580,7 @@ func (cart *atari16k) AccessVolatile(addr uint16, data uint8, poke bool) error {
 		}
 	}
 
-	return cart.atari.accessDriven(addr, data, poke)
+	return cart.atari.accessVolatile(addr, data, poke)
 }
 
 // bankswitch on hotspot access.
@@ -684,7 +684,7 @@ func (cart *atari32k) AccessVolatile(addr uint16, data uint8, poke bool) error {
 		}
 	}
 
-	return cart.atari.accessDriven(addr, data, poke)
+	return cart.atari.accessVolatile(addr, data, poke)
 }
 
 // bankswitch on hotspot access.
diff --git a/hardware/memory/cartridge/mapper_ef.go b/hardware/memory/cartridge/mapper_ef.go
index 4704f1be..770b2b33 100644
--- a/hardware/memory/cartridge/mapper_ef.go
+++ b/hardware/memory/cartridge/mapper_ef.go
@@ -83,7 +83,7 @@ func (cart *ef) AccessVolatile(addr uint16, data uint8, poke bool) error {
 		}
 	}
 
-	return cart.accessDriven(addr, data, poke)
+	return cart.accessVolatile(addr, data, poke)
 }
 
 // bankswitch on hotspot access.
diff --git a/hardware/memory/cartridge/mapper_tigervision.go b/hardware/memory/cartridge/mapper_tigervision.go
index a2deecfe..db395993 100644
--- a/hardware/memory/cartridge/mapper_tigervision.go
+++ b/hardware/memory/cartridge/mapper_tigervision.go
@@ -162,13 +162,6 @@ func (cart *tigervision) Patch(offset int, data uint8) error {
 
 // AccessPassive implements the mapper.CartMapper interface.
 func (cart *tigervision) AccessPassive(addr uint16, data uint8) error {
-	// tigervision is seemingly unique in that it bank switches when an address
-	// outside of cartridge space is written to. for this to work, we need the
-	// listen() function.
-	//
-	// update: tigervision is not unique. the 3e+ mapper also uses this
-	// mechanism. and superbank
-
 	// although address 3F is used primarily, in actual fact writing anywhere
 	// in TIA space is okay. from  the description from Kevin Horton's document
 	// (quoted above) whenever an address in TIA space is written to, the lower
diff --git a/hardware/memory/cartridge/mapper_ua.go b/hardware/memory/cartridge/mapper_ua.go
new file mode 100644
index 00000000..5ddf5604
--- /dev/null
+++ b/hardware/memory/cartridge/mapper_ua.go
@@ -0,0 +1,162 @@
+// This file is part of Gopher2600.
+//
+// Gopher2600 is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Gopher2600 is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Gopher2600.  If not, see <https://www.gnu.org/licenses/>.
+
+package cartridge
+
+import (
+	"crypto/sha1"
+	"fmt"
+
+	"github.com/jetsetilly/gopher2600/environment"
+	"github.com/jetsetilly/gopher2600/hardware/memory/cartridge/mapper"
+	"github.com/jetsetilly/gopher2600/hardware/memory/memorymap"
+	"github.com/jetsetilly/gopher2600/logger"
+)
+
+type ua struct {
+	env *environment.Environment
+
+	mappingID string
+
+	// ua cartridges are 8k in size and have two banks of 4096 bytes
+	bankSize int
+	banks    [][]uint8
+
+	// identifies the currently selected bank
+	bank int
+
+	// the hotspot addresses are swapped
+	swappedHotspots bool
+}
+
+func newUA(env *environment.Environment, data []byte) (mapper.CartMapper, error) {
+	cart := &ua{
+		env:             env,
+		mappingID:       "UA",
+		bankSize:        4096,
+		swappedHotspots: false,
+	}
+
+	if len(data) != cart.bankSize*cart.NumBanks() {
+		return nil, fmt.Errorf("UA: wrong number of bytes in the cartridge data")
+	}
+
+	cart.banks = make([][]uint8, cart.NumBanks())
+
+	for k := 0; k < cart.NumBanks(); k++ {
+		cart.banks[k] = make([]uint8, cart.bankSize)
+		offset := k * cart.bankSize
+		copy(cart.banks[k], data[offset:offset+cart.bankSize])
+	}
+
+	// only one cartridge dump is known to have swapped hotspots
+	if fmt.Sprintf("%0x", sha1.Sum(data)) == "6d4a94c2348bbd8e9c73b73d8f3389196d42fd54" {
+		cart.swappedHotspots = true
+		logger.Logf("UA", "swapping hotspot address for this cartridge (Sorcerer's Apprentice)")
+	}
+
+	return cart, nil
+}
+
+// MappedBanks implements the mapper.CartMapper interface
+func (cart *ua) MappedBanks() string {
+	return fmt.Sprintf("Bank: %d", cart.bank)
+}
+
+// ID implements the mapper.CartMapper interface
+func (cart *ua) ID() string {
+	return cart.mappingID
+}
+
+// Snapshot implements the mapper.CartMapper interface
+func (cart *ua) Snapshot() mapper.CartMapper {
+	n := *cart
+	return &n
+}
+
+// Plumb implements the mapper.CartMapper interface
+func (cart *ua) Plumb(env *environment.Environment) {
+	cart.env = env
+}
+
+// Reset implements the mapper.CartMapper interface
+func (cart *ua) Reset() {
+	cart.bank = len(cart.banks) - 1
+}
+
+// Access implements the mapper.CartMapper interface
+func (cart *ua) Access(addr uint16, _ bool) (uint8, uint8, error) {
+	return cart.banks[cart.bank][addr], mapper.CartDrivenPins, nil
+}
+
+// AccessVolatile implements the mapper.CartMapper interface
+func (cart *ua) AccessVolatile(addr uint16, data uint8, poke bool) error {
+	if poke {
+		cart.banks[cart.bank][addr] = data
+	}
+	return nil
+}
+
+// NumBanks implements the mapper.CartMapper interface
+func (cart *ua) NumBanks() int {
+	return 2
+}
+
+// GetBank implements the mapper.CartMapper interface
+func (cart *ua) GetBank(addr uint16) mapper.BankInfo {
+	// ua cartridges are like atari cartridges in that the entire address
+	// space points to the selected bank
+	return mapper.BankInfo{Number: cart.bank}
+}
+
+// Patch implements the mapper.CartMapper interface
+func (cart *ua) Patch(offset int, data uint8) error {
+	return fmt.Errorf("UA: patching unsupported")
+}
+
+// AccessPassive implements the mapper.CartMapper interface
+func (cart *ua) AccessPassive(addr uint16, data uint8) error {
+	switch addr & 0x1260 {
+	case 0x0220:
+		if cart.swappedHotspots {
+			cart.bank = 1
+		} else {
+			cart.bank = 0
+		}
+	case 0x0240:
+		if cart.swappedHotspots {
+			cart.bank = 0
+		} else {
+			cart.bank = 1
+		}
+	}
+	return nil
+}
+
+// Step implements the mapper.CartMapper interface
+func (cart *ua) Step(_ float32) {
+}
+
+// IterateBank implements the mapper.CartMapper interface
+func (cart *ua) CopyBanks() []mapper.BankContent {
+	c := make([]mapper.BankContent, len(cart.banks))
+	for b := 0; b < len(cart.banks); b++ {
+		c[b] = mapper.BankContent{Number: b,
+			Data:    cart.banks[b],
+			Origins: []uint16{memorymap.OriginCart},
+		}
+	}
+	return c
+}