Cyrix GXm

Cyrix GXm is a family of highly integrated microprocessors targeted for low-end systems. The GXm CPUs are based on 5x86 core and incorporate all of 5x86 core features: superpipelined (but not superscalar) micro-architecture, 16 KB level 1 write-back cache, integrated Floating Point Unit, branch prediction and ability to execute floating point instructions in parallel with integer instructions. In addition to 5x86 core features, the Cyrix GXm includes full set of MMX instructions and 12 extended MMX instructions. Like other Cyrix processors with the 5x86 core, the GXm processors have good integer performance and poor floating point performance.

Cyrix GXm processors were manufactured in 320-pin ceramic PGA package and 352-ball BGA package. Although the GXm microprocessors in ceramic PGA package fit into socket 7, they have completely different pinout and they do not work in that socket.

One of benefits of MediaGX CPUs is a large number of integrated peripherals. The CPU includes SDRAM memory controller, Display controller with 2D graphics accelerator, and PCI controller on the same chip. The CPU can be used together with Cx5520 or Cx5530 companion chips, which integrate the following:

• 16-bit stereo sound.
• IDE interface
• ISA interface
• AT compatibility logic
• Ultra DMA/33 interface (Cx5530 only)
• MPEG2 video accelerator (Cx5530 only)

Integrating many features in just two chips considerably reduces system cost. At the same time to reduce system cost Cyrix had to make certain design decisions, such as using part of main memory as video memory, or not including level 2 cache, that negatively affected system performance. As a result, Cyrix GXm-based system performs slower than similar clocked Pentium MMX or Pentium II system.