define what PCI stands for

architecture/README.md

@@ -73,7 +73,7 @@
     - latency: usually much higher than  CPU's ➔ the more parallel threads are run the less the price of high latency is paid (latency "hiding") 
     - spatial locality is extremely critical
   - A portion of the GPU-RAM is accessible to the CPU ➔ the GPU performs the copies
-  - The PCI-Bus bottleneck: data needs to flow from main (CPU) memory to GPU memory and back!
+  - The PCI-Bus (Peripheral Component Interconnect bus) is the bottleneck: data needs to flow from main (CPU) memory to GPU memory and back!
   - Problems on a cluster: the GPU does not really support simultanous multiple users payloads!
 
 # Computer Architecture (a concrete example)
@@ -94,7 +94,7 @@ My Laptop:
     - Internal clock 650 MHz, 1.54 ns
     - CAS Latency 34 cycles, Total latency = CAS latency x cycle = 13.09 ns, Throughput 40.6 GB/s
   - DMI (Direct Media Interface): 8×16 GT/s (≈128 GB/s)
-  - PCI Express bridges:
+  - PCI (Peripheral Component Interconnect) Express bridges:
     - Graphics: 16 GT/s (≈ 8 GB/s)
     - 2× Thunderbolt: 2.5 GT/s (≈ 1 GB/s) and 16 GT/s (≈ 8 GB/s)
   - GPU Intel Iris, Internal clock 300 Mhz-1.30 GHz, memory 4 GB/2.1 GHz with a bandwidth of 68 GB/s