I have been writing about various components and ICs found on the dell laptop motherboard. Following the powering sequence outlined in the note how laptops and PCs start up? I started taking note from the DC power input circuit to the I/O controller or KBC(Keyboard Controller) to Panther Point PCH(Platform Controller Hub) and the Ivy/Sandy Bridge Intel CPU. Yesterday I wrote about the DDR3(Double Data Rate 3) SDRAM and AMD Thames Pro ROBSON GPU that are connected to the CPU. The next important integrated circuit(IC) which is connected to the GPU is the VRAM (GDDR5) 128M x 16b x 4 (1GB). Here I wanted to write about the VRAM(Video RAM) used in my dell laptop.
Following circuit diagram shows the how the GPU is connected to the VRAM.
The "VRAM (GDDR5) 128M x 16b x 4 (1GB)" refers to the configuration of the dedicated video memory (VRAM) in the Dell laptop, which is connected to the AMD Thames Pro (Robson) GPU.
However my Dell laptop motherboard has an empty VRAM slot (unpopulated GDDR5 memory chips) and still works, depending on how the GPU is configured. Here’s what’s likely happening:
GPU Uses Shared System RAM (No Dedicated VRAM Installed)
Some laptops with AMD Thames Pro (Robson) GPUs (like the Radeon HD 8670M) can operate in "UMA mode" (Unified Memory Architecture), meaning they do not require dedicated VRAM and instead use shared system RAM (stolen from main memory).
If the GDDR5 chips are missing, the GPU may still work but with much lower performance since system RAM (DDR3/DDR4) is slower than GDDR5.
Here's a breakdown of what it means:
1. VRAM Type: GDDR5
GDDR5 (Graphics Double Data Rate 5) is a high-speed memory type designed for graphics processing.
It offers higher bandwidth compared to DDR3 or DDR4, making it better suited for gaming and GPU workloads.
2. Memory Organization: 128M x 16b
128M (Megawords) = 128 million memory locations.
16b (bits) = Each location stores 16 bits (2 bytes) of data.
Total per chip = 128M × 16b = 2 Gb (Gigabits) or 256 MB (Megabytes) per GDDR5 chip.
3. Number of Chips: ×4
There are 4 GDDR5 memory chips installed.
Total VRAM capacity = 256MB × 4 = 1GB (1024 MB).
4. AMD Thames Pro (Robson) GPU
This is an older AMD Radeon HD 7000M/8000M series GPU (likely HD 8670M or similar).
It was commonly used in mid-range laptops around 2012-2014.
Supports DirectX 11, OpenGL 4.2, and basic gaming/video tasks.
5. Bandwidth Calculation (Approximate)
If the GDDR5 runs at ~1000 MHz (effective 4000 MHz due to DDR):
Per chip bandwidth = 16b × 4000 MHz = 8 GB/s
Total (4 chips) = 8 GB/s × 4 = 32 GB/s
Conclusion
My Dell laptop has:
1GB of GDDR5 VRAM
4 memory chips (128M × 16b each)
~32 GB/s memory bandwidth (depending on clock speed)
AMD Thames Pro (Robson) GPU (likely Radeon HD 8670M class)
This setup was decent for light gaming (720p low/medium settings) and multimedia tasks at the time but is now considered outdated for modern gaming.
