Xilinx-Artix-7 FPGA

FPGA Upgrade: Artix-7 vs Spartan-6

The ZX Spectrum Next Kickstarter model KS2 (Issue 4 board) uses the Xilinx Artix-7 XC7A15T FPGA, replacing the Xilinx Spartan-6 XC6SLX16 FPGA used in the original KS1 (Issue 2B board). The Artix-7 is a more modern device, offering better performance, lower power consumption, and access to newer development tools.

The KS3 will use an Artix-7 XC7A35T-2 which pretty much doubles the logic cells, block RAM and DSP slices.

Below is a comparison between the three FPGAs:

Feature	Spartan-6 XC6SLX16 (KS1 - Issue 2B)	Artix-7 XC7A15T (KS2 - Issue 4)	Artix-7 XC7A35T-2 (KS3)
Technology Node	45 nm	28 nm	28nm
Logic Cells	~14,579	~16,640	~33,280
Flip-Flops	18,224	20,800	41,600
Block RAM	576 Kbits	918 Kbits	1,800 Kbits
DSP Slices	32	45	90
Power Consumption	Higher	Lower (static & dynamic)	Lower (static & dynamic)
Clock Management	PLL-based	MMCMs and PLLs (more flexible)	MMCMs and PLLs (more flexible)
Toolchain	Xilinx ISE (legacy)	Xilinx Vivado (modern)	Xilinx Vivado (modern)
Partial Reconfiguration	Not supported	Supported	Supported

Although the two FPGA models require different bitstreams due to the differing FPGA architectures, all systems are designed to remain feature-identical wherever possible in the Next Core to avoid splitting the user base. The KS2 and KS3 larger FPGA's could provide alternate cores with extra features - e.g. the Official QL core has Sprites on a KS2 to create an enhanced QL.

The only additions exclusive to KS2 (Issue 4) are four extra Category:Next Configuration Registers used for low-level hardware access:

• {{#ask:

TBRegisterNumber::$F0 }} ($F0) – XDEV CMD

• {{#ask:

TBRegisterNumber::$F8 }} ($F8) – XADC REG

• {{#ask:

TBRegisterNumber::$F9 }} ($F9) – XADC D0

• {{#ask:

TBRegisterNumber::$FA }} ($FA) – XADC D1

These registers allow developers to interact with internal Xilinx features such as the DNA ID and XADC (analog-to-digital converter). Technical documentation for these registers can be found on their respective pages.

External Links

• Xilinx Spartan-6 XC6SLX16 Data Sheet
• Xilinx Artix-7 XC7A15T CSG324-1 Data Sheet