GPUSTAT DMA Bits

Reads the DMA request and ready bits of GPUSTAT around a draw in each DMA direction.

GPUSTAT DMA Bits
Machine	SCPH-5501
Program	gpu/gpustat (ps1-tests)

This is an old revision of this page, as edited by RemmyLee at 05:18, 23 October 2026. Edit this revision | Latest revision

Overview

The program draws by CPU writes to GP0 and by a DMA list. It also draws by DMA in sync mode 1 with GP1(04h) direction 1 (FIFO) and with direction 2 (CPU to GP0). Before, during and after each draw it checks bits 25 to 30 of GPUSTAT against its own expected values.¹ The bits it checks are bit 25 (DMA request), bit 26 (ready to receive a command word), bit 27 (ready to send VRAM to the CPU), bit 28 (ready to receive a DMA block) and bits 29 and 30 (DMA direction).²

Results

In the runs from 27 September 2026 on, the SCPH-5501 passed all 13 checks.²

In the run of 25 September 2026 the check during a sync mode draw with direction 2 failed. GPUSTAT read bit 25 set (02000000h) and bit 28 set (10000000h), where the test expected both clear. The other 12 checks passed in that run.²

Runs

25 September 2026

07GST.txt

===== 07 GST GPU GPUSTAT | BIOS 19951204 System ROM Version 3.0 11/18/96 A

gpu/gpustat
Bits in GPUSTAT description:
Bit 25 - DMA Request 
  - When DMA Direction == 0 (Off) - always 0
  - When DMA Direction == 1 (FIFO) - ?
  - When DMA Direction == 2 (CPUtoGP0) - same as Bit 28
  - When DMA Direction == 3 (GPUREADtoCPU) - same as Bit 27
Bit 26 - Ready to receive Cmd Word
Bit 27 - Ready to send VRAM to CPU
Bit 28 - Ready to receive DMA Block
Bits 29-30 - DMA Direction (0 - Off, 1 - FIFO, 2 - CPUtoGP0, 3 - GPUREADtoCPU)

pass - testGpustat_CPU_beforeRender
pass - testGpustat_CPU_duringRender
pass - testGpustat_CPU_afterRender
pass - testGpustat_linkedListDMA_beforeRender
pass - testGpustat_LinkedListDMA_duringRender
pass - testGpustat_LinkedListDMA_afterRender
pass - testGpustat_SyncModeDMA_dir1_beforeRender
pass - testGpustat_SyncModeDMA_dir1_duringRender
pass - testGpustat_SyncModeDMA_dir1_afterRender
pass - testGpustat_SyncModeDMA_dir2_beforeRender
fail - testGpustat_SyncModeDMA_dir2_duringRender:254 `(stat) & (1 << 25) == 0 << 25`, given: 0x2000000, expected: 0x0 
fail - testGpustat_SyncModeDMA_dir2_duringRender:257 `(stat) & (1 << 28) == 0 << 28`, given: 0x10000000, expected: 0x0 
pass - testGpustat_SyncModeDMA_dir2_afterRender
Done.

27 September 2026

07GST.txt

===== 07 GST GPU GPUSTAT | BIOS 19951204 System ROM Version 3.0 11/18/96 A

gpu/gpustat
Bits in GPUSTAT description:
Bit 25 - DMA Request 
  - When DMA Direction == 0 (Off) - always 0
  - When DMA Direction == 1 (FIFO) - ?
  - When DMA Direction == 2 (CPUtoGP0) - same as Bit 28
  - When DMA Direction == 3 (GPUREADtoCPU) - same as Bit 27
Bit 26 - Ready to receive Cmd Word
Bit 27 - Ready to send VRAM to CPU
Bit 28 - Ready to receive DMA Block
Bits 29-30 - DMA Direction (0 - Off, 1 - FIFO, 2 - CPUtoGP0, 3 - GPUREADtoCPU)

pass - testGpustat_CPU_beforeRender
pass - testGpustat_CPU_duringRender
pass - testGpustat_CPU_afterRender
pass - testGpustat_linkedListDMA_beforeRender
pass - testGpustat_LinkedListDMA_duringRender
pass - testGpustat_LinkedListDMA_afterRender
pass - testGpustat_SyncModeDMA_dir1_beforeRender
pass - testGpustat_SyncModeDMA_dir1_duringRender
pass - testGpustat_SyncModeDMA_dir1_afterRender
pass - testGpustat_SyncModeDMA_dir2_beforeRender
pass - testGpustat_SyncModeDMA_dir2_duringRender
pass - testGpustat_SyncModeDMA_dir2_afterRender
Done.

27 September 2026 run 2

07GST.txt

===== 07 GST GPU GPUSTAT | BIOS 19951204 System ROM Version 3.0 11/18/96 A

gpu/gpustat
Bits in GPUSTAT description:
Bit 25 - DMA Request 
  - When DMA Direction == 0 (Off) - always 0
  - When DMA Direction == 1 (FIFO) - ?
  - When DMA Direction == 2 (CPUtoGP0) - same as Bit 28
  - When DMA Direction == 3 (GPUREADtoCPU) - same as Bit 27
Bit 26 - Ready to receive Cmd Word
Bit 27 - Ready to send VRAM to CPU
Bit 28 - Ready to receive DMA Block
Bits 29-30 - DMA Direction (0 - Off, 1 - FIFO, 2 - CPUtoGP0, 3 - GPUREADtoCPU)

pass - testGpustat_CPU_beforeRender
pass - testGpustat_CPU_duringRender
pass - testGpustat_CPU_afterRender
pass - testGpustat_linkedListDMA_beforeRender
pass - testGpustat_LinkedListDMA_duringRender
pass - testGpustat_LinkedListDMA_afterRender
pass - testGpustat_SyncModeDMA_dir1_beforeRender
pass - testGpustat_SyncModeDMA_dir1_duringRender
pass - testGpustat_SyncModeDMA_dir1_afterRender
pass - testGpustat_SyncModeDMA_dir2_beforeRender
pass - testGpustat_SyncModeDMA_dir2_duringRender
pass - testGpustat_SyncModeDMA_dir2_afterRender
Done.

27 September 2026 run 3

07GST.txt

===== 07 GST GPU GPUSTAT | BIOS 19951204 System ROM Version 3.0 11/18/96 A

gpu/gpustat
Bits in GPUSTAT description:
Bit 25 - DMA Request 
  - When DMA Direction == 0 (Off) - always 0
  - When DMA Direction == 1 (FIFO) - ?
  - When DMA Direction == 2 (CPUtoGP0) - same as Bit 28
  - When DMA Direction == 3 (GPUREADtoCPU) - same as Bit 27
Bit 26 - Ready to receive Cmd Word
Bit 27 - Ready to send VRAM to CPU
Bit 28 - Ready to receive DMA Block
Bits 29-30 - DMA Direction (0 - Off, 1 - FIFO, 2 - CPUtoGP0, 3 - GPUREADtoCPU)

pass - testGpustat_CPU_beforeRender
pass - testGpustat_CPU_duringRender
pass - testGpustat_CPU_afterRender
pass - testGpustat_linkedListDMA_beforeRender
pass - testGpustat_LinkedListDMA_duringRender
pass - testGpustat_LinkedListDMA_afterRender
pass - testGpustat_SyncModeDMA_dir1_beforeRender
pass - testGpustat_SyncModeDMA_dir1_duringRender
pass - testGpustat_SyncModeDMA_dir1_afterRender
pass - testGpustat_SyncModeDMA_dir2_beforeRender
pass - testGpustat_SyncModeDMA_dir2_duringRender
pass - testGpustat_SyncModeDMA_dir2_afterRender
Done.

27 September 2026 run 4

07GST.txt

===== 07 GST GPU GPUSTAT | BIOS 19951204 System ROM Version 3.0 11/18/96 A

gpu/gpustat
Bits in GPUSTAT description:
Bit 25 - DMA Request 
  - When DMA Direction == 0 (Off) - always 0
  - When DMA Direction == 1 (FIFO) - ?
  - When DMA Direction == 2 (CPUtoGP0) - same as Bit 28
  - When DMA Direction == 3 (GPUREADtoCPU) - same as Bit 27
Bit 26 - Ready to receive Cmd Word
Bit 27 - Ready to send VRAM to CPU
Bit 28 - Ready to receive DMA Block
Bits 29-30 - DMA Direction (0 - Off, 1 - FIFO, 2 - CPUtoGP0, 3 - GPUREADtoCPU)

pass - testGpustat_CPU_beforeRender
pass - testGpustat_CPU_duringRender
pass - testGpustat_CPU_afterRender
pass - testGpustat_linkedListDMA_beforeRender
pass - testGpustat_LinkedListDMA_duringRender
pass - testGpustat_LinkedListDMA_afterRender
pass - testGpustat_SyncModeDMA_dir1_beforeRender
pass - testGpustat_SyncModeDMA_dir1_duringRender
pass - testGpustat_SyncModeDMA_dir1_afterRender
pass - testGpustat_SyncModeDMA_dir2_beforeRender
pass - testGpustat_SyncModeDMA_dir2_duringRender
pass - testGpustat_SyncModeDMA_dir2_afterRender
Done.

28 September 2026

07GST.txt

===== 07 GST GPU GPUSTAT | BIOS 19951204 System ROM Version 3.0 11/18/96 A

gpu/gpustat
Bits in GPUSTAT description:
Bit 25 - DMA Request 
  - When DMA Direction == 0 (Off) - always 0
  - When DMA Direction == 1 (FIFO) - ?
  - When DMA Direction == 2 (CPUtoGP0) - same as Bit 28
  - When DMA Direction == 3 (GPUREADtoCPU) - same as Bit 27
Bit 26 - Ready to receive Cmd Word
Bit 27 - Ready to send VRAM to CPU
Bit 28 - Ready to receive DMA Block
Bits 29-30 - DMA Direction (0 - Off, 1 - FIFO, 2 - CPUtoGP0, 3 - GPUREADtoCPU)

pass - testGpustat_CPU_beforeRender
pass - testGpustat_CPU_duringRender
pass - testGpustat_CPU_afterRender
pass - testGpustat_linkedListDMA_beforeRender
pass - testGpustat_LinkedListDMA_duringRender
pass - testGpustat_LinkedListDMA_afterRender
pass - testGpustat_SyncModeDMA_dir1_beforeRender
pass - testGpustat_SyncModeDMA_dir1_duringRender
pass - testGpustat_SyncModeDMA_dir1_afterRender
pass - testGpustat_SyncModeDMA_dir2_beforeRender
pass - testGpustat_SyncModeDMA_dir2_duringRender
pass - testGpustat_SyncModeDMA_dir2_afterRender
Done.

References

^ ps1-tests, gpu/gpustat. https://github.com/JaCzekanski/ps1-tests.
^ ^a ^b ^c SCPH-5501 output: main/07GST.txt and the files beside it, with the other runs listed under Runs.

Categories: Hardware tests