diff --git a/app/api/util.ts b/app/api/util.ts
index ea227eb65..fea182b7b 100644
--- a/app/api/util.ts
+++ b/app/api/util.ts
@@ -23,13 +23,13 @@ import type {
   VpcFirewallRuleUpdate,
 } from './__generated__/Api'
 
-// API limits encoded in https://github.com/oxidecomputer/omicron/blob/main/nexus/src/app/mod.rs
+// API limits encoded in https://github.com/oxidecomputer/omicron/blob/b7af5f8e/nexus/src/app/mod.rs
 
 export const MAX_NICS_PER_INSTANCE = 8
 
 export const INSTANCE_MAX_CPU = 64
 export const INSTANCE_MIN_RAM_GiB = 1
-export const INSTANCE_MAX_RAM_GiB = 256
+export const INSTANCE_MAX_RAM_GiB = 1024
 
 export const MIN_DISK_SIZE_GiB = 1
 /**
diff --git a/app/forms/instance-create.tsx b/app/forms/instance-create.tsx
index ca4e39efa..7c0bf3f58 100644
--- a/app/forms/instance-create.tsx
+++ b/app/forms/instance-create.tsx
@@ -432,14 +432,13 @@ export default function CreateInstanceForm() {
               label="CPUs"
               name="ncpus"
               min={1}
-              max={INSTANCE_MAX_CPU}
               control={control}
               validate={(cpus) => {
                 if (cpus < 1) {
                   return `Must be at least 1 vCPU`
                 }
                 if (cpus > INSTANCE_MAX_CPU) {
-                  return `CPUs capped to ${INSTANCE_MAX_CPU}`
+                  return `Can be at most ${INSTANCE_MAX_CPU}`
                 }
               }}
               disabled={isSubmitting}
@@ -450,7 +449,6 @@ export default function CreateInstanceForm() {
               label="Memory"
               name="memory"
               min={1}
-              max={INSTANCE_MAX_RAM_GiB}
               control={control}
               validate={(memory) => {
                 if (memory < 1) {
diff --git a/app/pages/project/instances/InstancePage.tsx b/app/pages/project/instances/InstancePage.tsx
index f04931327..d69c5a5f8 100644
--- a/app/pages/project/instances/InstancePage.tsx
+++ b/app/pages/project/instances/InstancePage.tsx
@@ -374,7 +374,7 @@ export function ResizeInstanceModal({
                   return `Must be at least 1 vCPU`
                 }
                 if (cpus > INSTANCE_MAX_CPU) {
-                  return `CPUs capped to ${INSTANCE_MAX_CPU}`
+                  return `Can be at most ${INSTANCE_MAX_CPU}`
                 }
                 // We can show this error and therefore inform the user
                 // of the limit rather than preventing it completely
diff --git a/mock-api/msw/handlers.ts b/mock-api/msw/handlers.ts
index 54405c318..b1caf43fe 100644
--- a/mock-api/msw/handlers.ts
+++ b/mock-api/msw/handlers.ts
@@ -412,11 +412,8 @@ export const handlers = makeHandlers({
 
     const instanceId = uuid()
 
-    // TODO: These values should ultimately be represented in the schema and
-    // checked with the generated schema validation code.
-
     if (body.memory > INSTANCE_MAX_RAM_GiB * GiB) {
-      throw `Memory must be less than ${INSTANCE_MAX_RAM_GiB} GiB`
+      throw `Memory can be at most ${INSTANCE_MAX_RAM_GiB} GiB`
     }
 
     if (body.memory < INSTANCE_MIN_RAM_GiB * GiB) {
diff --git a/test/e2e/instance-create.e2e.ts b/test/e2e/instance-create.e2e.ts
index 8d0cd614a..c93ce63d4 100644
--- a/test/e2e/instance-create.e2e.ts
+++ b/test/e2e/instance-create.e2e.ts
@@ -613,3 +613,37 @@ test('create instance with additional disks', async ({ page }) => {
   await expectRowVisible(otherDisksTable, { Disk: 'new-disk-1', size: '5 GiB' })
   await expectRowVisible(otherDisksTable, { Disk: 'disk-3', size: '6 GiB' })
 })
+
+test('Validate CPU and RAM', async ({ page }) => {
+  await page.goto('/projects/mock-project/instances-new')
+
+  await page.getByRole('textbox', { name: 'Name', exact: true }).fill('db2')
+  await selectASiloImage(page, 'ubuntu-22-04')
+
+  await page.getByRole('tab', { name: 'Custom' }).click()
+
+  const cpu = page.getByRole('textbox', { name: 'CPU' })
+  await cpu.fill('999')
+
+  // blur CPU
+  const memory = page.getByRole('textbox', { name: 'Memory' })
+  await memory.click()
+
+  // make sure it's not clamping the value
+  await expect(cpu).toHaveValue('999')
+
+  await memory.fill('1025')
+
+  const submitButton = page.getByRole('button', { name: 'Create instance' })
+
+  const cpuMsg = page.getByText('Can be at most 64').first()
+  const memMsg = page.getByText('Can be at most 1024 GiB').first()
+
+  await expect(cpuMsg).toBeHidden()
+  await expect(memMsg).toBeHidden()
+
+  await submitButton.click()
+
+  await expect(cpuMsg).toBeVisible()
+  await expect(memMsg).toBeVisible()
+})