diff --git a/lua/entities/gmod_wire_cpu.lua b/lua/entities/gmod_wire_cpu.lua
index 853d1fa..b9b0b26 100644
--- a/lua/entities/gmod_wire_cpu.lua
+++ b/lua/entities/gmod_wire_cpu.lua
@@ -140,7 +140,12 @@ local memoryModels = {
 	["flat"]    = {      0, 0      },
 }
 
-function ENT:SetMemoryModel(model)
+function ENT:SetMemoryModel(model,cram,crom)
+	if model == "custom" then
+		self.VM.RAMSize = (tonumber(cram) or 512)*128 -- 65536
+		self.VM.ROMSize = (tonumber(crom) or 512)*128 -- 65536
+		return
+	end
 	self.VM.RAMSize = memoryModels[model][1] or 65536
 	self.VM.ROMSize = memoryModels[model][2] or 65536
 end
diff --git a/lua/wire/stools/cpu.lua b/lua/wire/stools/cpu.lua
index 2d0aa7e..118c89f 100644
--- a/lua/wire/stools/cpu.lua
+++ b/lua/wire/stools/cpu.lua
@@ -19,7 +19,9 @@ TOOL.ClientConVar = {
   model             = "models/cheeze/wires/cpu.mdl",
   filename          = "",
   memorymodel       = "64krom",
-  extensions        = ""
+  extensions        = "",
+  customram         = 0,
+  customrom         = 0
 }
 
 if CLIENT then
@@ -46,7 +48,7 @@ if SERVER then
     if player:KeyDown(IN_SPEED) then
       if (trace.Entity:IsValid()) and
          (trace.Entity:GetClass() == "gmod_wire_cpu") then
-        trace.Entity:SetMemoryModel(self:GetClientInfo("memorymodel"))
+        trace.Entity:SetMemoryModel(self:GetClientInfo("memorymodel"),self:GetClientInfo("customram"),self:GetClientInfo("customrom"))
         trace.Entity:FlashData({})
         net.Start("CPULib.InvalidateDebugger") net.WriteUInt(0,2) net.Send(player)
       end
@@ -76,7 +78,7 @@ if SERVER then
   end
   function TOOL:MakeEnt(ply, model, Ang, trace)
     local ent = WireLib.MakeWireEnt(ply, {Class = self.WireClass, Pos=trace.HitPos, Angle=Ang, Model=model})
-    ent:SetMemoryModel(self:GetClientInfo("memorymodel"))
+    ent:SetMemoryModel(self:GetClientInfo("memorymodel"),self:GetClientInfo("customram"),self:GetClientInfo("customrom"))
     ent:SetExtensionLoadOrder(self:GetClientInfo("extensions"))
     self:LeftClick_Update(trace)
     return ent
@@ -181,7 +183,7 @@ if CLIENT then
 
 
     ----------------------------------------------------------------------------
-    panel:AddControl("ComboBox", {
+    local memPanel = panel:AddControl("ComboBox", {
       Label = "Memory model",
       Options = {
         ["128 bytes ROM only"]  = {wire_cpu_memorymodel = "128rom"},
@@ -194,9 +196,29 @@ if CLIENT then
         ["8KB RAM only"]        = {wire_cpu_memorymodel = "8k"},
         ["128KB RAM/ROM"]       = {wire_cpu_memorymodel = "128krom"},
         ["No internal RAM/ROM"] = {wire_cpu_memorymodel = "flat"},
+        ["Custom RAM/ROM"]      = {wire_cpu_memorymodel = "custom"},
       }
     })
     panel:AddControl("Label", {Text = "Sets the processor memory model (determines interaction with the external devices)"})
+    local customMemPanel = {
+      panel:AddControl("Label", {Text = "Custom memory size for RAM and ROM is in pages(128 bytes)"}),
+      panel:AddControl("Slider", {Label = "RAM size", Command = "wire_cpu_customram", Min = 0, Max = 1024}),
+      panel:AddControl("Slider", {Label = "ROM size", Command = "wire_cpu_customrom", Min = 0, Max = 1024}),
+    }
+    local memoryModel = GetConVar("wire_cpu_memorymodel")
+    function memPanel:OnSelect(index, value, data)
+      if data.wire_cpu_memorymodel == "custom" then
+        for _,i in ipairs(customMemPanel) do
+          i:Show()
+        end
+      else
+        for _,i in ipairs(customMemPanel) do
+          i:Hide()
+        end
+      end
+      -- Overriding this turns off the automatic convar write, so we have to do it ourselves.
+        memoryModel:SetString(data.wire_cpu_memorymodel)
+    end
 
     local enabledExtensionOrder = {}
     local enabledExtensionLookup = {}