• 150 mA for TMS9995 CPU
• 100 mA for TMS9902 UART
• 23 mA for 32K RAM HM62256LP-10
• 10 mA for 32K ROM
• 7 mA for 74LS04
• 10 mA for 74LS32
• 10 mA for 74LS138
• 310 mA total

The L suffix of the HM62256L indicating "low power" refers the the standby current. In normal operation, it consumes as much power as the normal-power part. The power is 40 milliwatts at 1 MHz,  which is 8 mA at 5 volts. However, the current-frequency graph indicates a linear relationship. The 85 ns part consumes 100% of 70 mA at full speed (10 MHz)  and about 25% (17 mA) at 2 MHz. A TMS9995 with 12 MHz crystal has a 3 MHz cycle rate which sets an upper bound of around 23 mA.

The currents above exceed the 100 mA of the minimum power USB peripheral, so I have not joined the VCC rail to the VCC of the USB cable connector.