Took me some effort to get that, so maybe these 2 functions can be useful for others as well:

uses
  ... , Unix, sysctl ...;

...

function GetCPUBrandAndModel: AnsiString;
var
  CharLen : size_t;
  cpuChar : PChar;
begin
  Result :='Unknown CPU';

  if fpSysCtlByName('machdep.cpu.brand_string', Nil, @CharLen, Nil, 0)<>0 then exit;

  cpuChar := GetMem(CharLen);

  try
    if fpSysCtlByName('machdep.cpu.brand_string', cpuChar, @CharLen, Nil, 0)=0 then
      Result := cpuChar;
  finally
    FreeMem(cpuChar);
  end;
end;


function GetCPUArchitecture: AnsiString;
var
  mib     : array of Integer;
  CharLen : size_t;
  cpuArch : PChar;
begin
  mib := CTL_HW;
  mib := HW_MACHINE;

  if fpSysCtl(PCInt(@mib), Length(mib), Nil, @CharLen, Nil, 0)<>0 then exit;

  cpuArch := GetMem(CharLen);

  try
    if fpSysCtl(PCInt(@mib), Length(mib), cpuArch, @CharLen, Nil, 0)=0 then
     Result := cpuArch;
  finally
    FreeMem(cpuArch);
  end;
end;


...

// Example call:
  ShowMessage('CPU Brand and Model: ' + GetCPUBrandAndModel + LineEnding + LineEnding + 'CPU Architecture: ' + GetCPUArchitecture);