It will be slower. You;'ll get somewhere between 50-75mbps transfer rate. You are limited by the bus.
Your Mac originally came with a Rage 128 video card. Since you want cheap, I'd try and find another one of those. They are about the cheapest (both in price and quality) cards you can get for this machine. You'd be overcharged if someone wanted $10 for one.
Sorry mate, but in this instance, you're under a bit of a misconception:
The expected maximum throughput on PCI-33 is roughly
133MB/s, which is the highest DRT possible with ATA-6 (ATA/133), although the
ATA bus on the G4 systems is ATA/100, which is 100MB/s, not 100Mb/s (it's 800Mb/s, or the same speed as FW800).
Firewire 400 has a DRT maximum of 400M
b/s, or
50MB/s, which is dramatically less than using the PCI bus, via either a SATA or a PATA controller. Now, you won;t see the full 133MB/s DTR in most cases, but you can expect at least half of that in any given instance, or roughly 67MB/s (536Mb/s), which still
outperforms the maximum DTR of Firewire 400.
Then, you need to calculate that FW400 loses some total bandwidth in exchange through various bus controllers (latency). A SATA or PATA card should outperform FW400 in most cases, unless there is significant latency on the PCI bus, as
the entire bandwidth of the PCI bus is shared with all devices connected to it.
You would see an improvement with a SATA card, over FW400, but not much of a difference in contrast to the internal PATA bus with ATA/100 drives. What you can achieve with PCI-33 and SATA is eSATA, with nearly identical performance to the internal HDDs, but the more drives that you add to it, the more you hamper the performance.
The main problem is that all PCI devices, all FW devices, and all ATA devices are routed through the same Southbridge, so the more you add to a system, the more you hinder the performance of the entire bus architecture. AGP is via the Northbridge, so systems with AGP video cards do not suffer the same problem, but systems with only PCI or PCI-X do. (Ethernet, and USB are also routed through the Southbridge controller.)
I don;t know what the maximum throughput is, on the Souhtbridge on this system, off hand, but I would expect that it has the capability of driving the PCI bus, and the other systems routed through it at roughly equal speed, and with equal bandwidth; however, I cant be certain of that without testing it.
You want to
avoid a PCI graphics card, and use an AGP card, tro maximise the amount of bandwidth available to PCI devices, and avoid unnecessary use of the FW and USB buses to lower the load ont he Southbridge. That will give your on-board ATA, and PCI buses a marked improvement; especially if you want to use any PCI cards, such as an eSATA card.
You will need PCI-33 cards, and you will not find a USB 3.0 card in that format. Locating a PCI-33 SATA card is not difficult, but most will not boot the system. You can modify the firmware on some, to allow them to boot the system, however if you are not concerned with booting the system, a decent PCI-33 SATA card is useful for adding additional volumes.
You also needn't worry if the card has a header for eSATA, as you an always buy an eSATA header, mount it in an empty slot, and attach it with a cable to a port normally used for an internal SATA device.
If the HDD from the MBP is SATA-II, it would work on PCI-33 SATA cards, however if it is SATA-III, it
may not. In any event, a PCI SATA card is not much of an improvement over the on-board ATA/100 bus, and you would not see the full potential of SATA/150 mechanisms, as they would be hampered by the PCI-33 bus, down to the same level of performance as ATA/133 devices, and further, due to shared bandwidth.
The only advantage is that SATA devices are easier, and less expensive to obtain than PATA devices, especially in capacities =>500GB. The largest PATA drives were 750GB, and those are both quite rare, and expensive; and of course, are likely to be used, with a limited lifespan.
