They are quite different. The Duron 1300 is based on the 0.18 micron Morgan core and uses a 100MHz (DDR200) FSB. The Duron 1300 will practically run on any socket A motherboard you can find. The Duron 1400 is based on the 0.13 micron Applebred core and uses a 133MHz (DDR266) FSB. It will require a motherboard that is able to run with 133MHz FSB and able to 'understand' 0.13 micron CPU's so the Duron 1400 won't run on all early socket A motherboards.

The Duron 1400 is actually an Athlon XP Thoroughbred but with parts of the L2-cache disabled. Physically it still has the Athlon XP core but the CPU is configured to run with 64KB L2-cache. In some cases the Duron 1400 is, in terms of performance, equal to the Athlon XP 1600+ (1400MHz, DDR266) and in some cases it falls behind because of the reduced L2-cache. The early versions of the Duron Applebred can be modified to work as Athlon XP if you're lucky and usually the Duron Applebred is quite a good overclocker whereas the Duron Morgan is already clocked near it's maximum (and run's a lot hotter).

Well ..I guess I can only hope the 1300 Morgan will work in my board ..
I am a bit confused already tbh ..as It currently is running a Duron 950 ..which is out of spec according to the manual ..
Unless I'm misunderstanding something..
This is an extract from the manual.

>>>
Support AMD Athlon 700∼1GHz processor
∗ Support AMD Duron 600∼750MHz processor
∗ Support 100MHz F.S.B.
∗ Support 200MHz (Double Data Rate)
∗ Reserves support for future AMD Athlon/Duron processors
>>>

I guess the getout is the last line which includes the word 'reserves'

maybe I should look at Athlon cpus instead ?

Thanks for the explanation btw

What board is it?

Well, it may support more than that with a newer BIOS. Maybe your particular board does already have a newer BIOS than the quoted manual. And it may even boot with CPUs that "aren't supported". I've seen an Abit KT7A run with a Barton, the last iteration of the K7 family. It detected it as "unknown CPU" but it worked with it.

(Unlike my H67 board that just wouldn't POST with the Ivy Xeon that I write on now, after a BIOS upgrade.)

Mobo is a Jetway 663AS

CPU INFO
CENTRAL PROCESSING UNITS
Manufacturer AMD
Family Duron(tm)
Internal Clock 952 MHz
Internal Clock Maximum 952 MHz
External Clock 100 MHz
Socket Designation Socket A
Type <unknown>
Upgrade Slot 1
Capabilities MMX, CMov, RDTSC, 3DNow!, Extended 3DNow!
Version AMD Duron(TM)
CPUID 0x00000631

MOTHERBOARD INFO
Manufacturer
Model 8363-686A/B
Version N/A
BIOS Vendor Award Software International, Inc.
BIOS Version 6.00 PG
BIOS Release Date 03/26/2001
BIOS Properties Plug and Play, Flash, AGP

Vipersan wrote:

Mobo is a Jetway 663AS

According to CPU-Upgrade (a grain of salt is always advised) it can handle any Spitfire/Morgan Duron but and Applebred won't cut it.
So the 1300 should be okay but the 1400 wont't work or will - but slower than specified.